Hysteresis loops of spin-dependent electronic current in a paramagnetic resonant tunnelling diode

International Nuclear Information System (INIS)

Wójcik, P; Spisak, B J; Wołoszyn, M; Adamowski, J

2012-01-01

Nonlinear properties of the spin-dependent electronic transport through a semiconductor resonant tunnelling diode with a paramagnetic quantum well are considered. The spin-dependent Wigner–Poisson model of the electronic transport and the two-current Mott’s formula for the independent spin channels are applied to determine the current–voltage curves of the nanodevice. Two types of the electronic current hysteresis loops are found in the current–voltage characteristics for both the spin components of the electronic current. The physical interpretation of these two types of the electronic current hysteresis loops is given based on the analysis of the spin-dependent electron densities and the potential energy profiles. The differences between the current–voltage characteristics for both the spin components of the electronic current allow us to explore the changes of the spin polarization of the current for different electric fields and determine the influence of the electronic current hysteresis on the spin polarization of the current flowing through the paramagnetic resonant tunnelling diode. (paper)

Three-Dimensional Phase Field Simulations of Hysteresis and Butterfly Loops by the Finite Volume Method

International Nuclear Information System (INIS)

Xi Li-Ying; Chen Huan-Ming; Zheng Fu; Gao Hua; Tong Yang; Ma Zhi

2015-01-01

Three-dimensional simulations of ferroelectric hysteresis and butterfly loops are carried out based on solving the time dependent Ginzburg–Landau equations using a finite volume method. The influence of externally mechanical loadings with a tensile strain and a compressive strain on the hysteresis and butterfly loops is studied numerically. Different from the traditional finite element and finite difference methods, the finite volume method is applicable to simulate the ferroelectric phase transitions and properties of ferroelectric materials even for more realistic and physical problems. (paper)

Thermal Hysteresis Loop, Dynamical Breakdown, and Emission-Current Spike in Quantum-Well Photodetectors

National Research Council Canada - National Science Library

Huang, Danhong

2001-01-01

.... For the time-dependent temperature, a counterclockwise hysteresis loop in the tunneling current as a function of the swept temperature is predicted and attributed to a blockade or an enhancement...

Asymmetrically shaped hysteresis loop in exchange-biased FeNi/FeMn film

International Nuclear Information System (INIS)

Gnatchenko, S.L.; Merenkov, D.N.; Bludov, A.N.; Pishko, V.V.; Shakhayeva, Yu.A.; Baran, M.; Szymczak, R.; Novosad, V.A.

2006-01-01

The magnetization reversal of the bilayer polycrystalline FeNi(50 A)/FeMn(50 A) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field applied along the easy axis. The specific features of magnetization reversal were explained within the phenomenological model that involves high-order exchange anisotropy and misalignment of the easy axes of the antiferromagnetic and ferromagnetic layers. It has been shown that the film can exist in one of three equilibrium magnetic states in the field applied along the easy axis. The transitions between these states occur as first-order phase transitions. The observed hysteresis loop asymmetry is related to the existence of the metastable state

Open-loop position tracking control of a piezoceramic flexible beam using a dynamic hysteresis compensator

International Nuclear Information System (INIS)

Nguyen, Phuong-Bac; Choi, Seung-Bok

2010-01-01

This paper proposes a novel hysteresis compensator to enhance control accuracy in open-loop position tracking control of a piezoceramic flexible beam. The proposed hysteresis compensator consists of two components: a rate-independent hysteresis compensator and a nonlinear filter. The compensator is formulated based on the inverse Preisach model, while the weight coefficients of the filter are identified adaptively using a recursive least square (RLS) algorithm. In this work, two dynamic hysteresis compensators (or rate-independent hysteresis compensators) are developed by adopting two different nonlinear filters: Volterra and bilinear filters. In order to demonstrate the improved control accuracy of the proposed dynamic compensators, a flexible beam associated with the piezoceramic actuator is modeled using the finite element method (FEM) and Euler–Bernoulli beam theory. The beam model is then integrated with the proposed hysteresis model to achieve accurate position tracking control at the tip of the beam. An experimental investigation on the tip position tracking control is undertaken by realizing three different hysteresis compensators: a rate-independent hysteresis compensator, a rate-dependent hysteresis compensator with a Volterra nonlinear filter and a rate-independent hysteresis compensator with a bilinear nonlinear filter. It is shown that the proposed dynamic hysteresis compensators can provide much better tracking control accuracy than conventional rate-independent hysteresis compensators

Investigation of scaling laws in frequency-dependent minor hysteresis loops for ferromagnetic steels

International Nuclear Information System (INIS)

Kobayashi, S.; Tsukidate, S.; Kamada, Y.; Kikuchi, H.; Ohtani, T.

2012-01-01

Scaling laws in dynamical magnetic minor hysteresis loops have been investigated in the magnetizing frequency range of 0.05-300 Hz for various steels including Cr-Mo-V steel subjected to creep, cold rolled steels, and plastically deformed Ni. Although scaling laws in the medium magnetization range found previously fail in the high magnetization frequency regime owing to a significant contribution of eddy currents, a scaling power law of the relation between remanence and remanence work of minor loops, associated with a constant exponent of approximately 1.9, holds true in a very low magnetization regime, irrespective of magnetization frequency and investigated materials. The coefficient of the law is proportionally related to Vickers hardness over the wide frequency range. These observations demonstrate that the scaling analysis of dynamical minor loops enables us to evaluate materials degradation in a short measurement time with low measurement field and high sensitivity to defect density. - Highlights: → We performed hysteresis scaling for dynamical minor loops in ferromagnetic steels. → An universal scaling power law with an exponent of 1.9 was observed. → Coefficient of the scaling law reflects defect density due to creep and deformation. → This method is useful for on-line non-destructive evaluation.

Impact of choice of stabilized hysteresis loop on the end result of investigation of high-strength low-alloy (HSLA steel on low cycle fatigue

Directory of Open Access Journals (Sweden)

S. Bulatović

2014-10-01

Full Text Available High strength low-alloy steel under low cycle fatigue at a certain level of strain controlled achieve stabilized condition. During the fatigue loading stabilized hysteresis loop is determined, which typical cycle of stabilization is calculated as half number of cycles to failure. Stabilized hysteresis loop is a representative of all hysteresis and it’s used to determine all of the parameters for the assessment of low cycle fatigue. This paper shows comparison of complete strain-life curves of low cycle fatigue for two chosen stabilized hysteresis loop cycles of base metal HSLA steel marked as Nionikral 70.

A mechanical brake hardware-in-the-loop simulation of a railway vehicle that accounts for hysteresis and pneumatic cylinder dynamics

Directory of Open Access Journals (Sweden)

Dong-Chan Lee

2015-11-01

Full Text Available A brake hardware-in-the-loop simulation system for a railway vehicle provides an effective platform for testing the braking performance under various dangerous braking conditions. However, in general, four-brake calipers are required to implement a mechanical brake system for one car. In this article, we implement a brake hardware-in-the-loop simulation system only with one brake caliper and three air tanks accounting for hysteresis and pneumatic cylinder dynamics, ultimately saving installation space and reducing financial budget costs. Since the brake caliper has a high nonlinearity, such as hysteresis resulting from friction and from the precompressed spring of the brake cylinder, we measured the hysteresis of the brake caliper clamping force for a mechanical brake system using loadcells, based on which a mathematical model was constructed for the hysteresis of the clamping force between the brake pad and the disk. Moreover, the pneumatic cylinder dynamics are identified and are implemented in three air tanks, together with hysteresis nonlinearity. The proposed brake hardware-in-the-loop simulation system is applied to the wheel-slide protection simulation of a railway vehicle with an initial speed of 80 km/h and demonstrated experimentally accounting for the hysteresis and brake cylinder dynamics.

Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles

International Nuclear Information System (INIS)

Iglesias, Oscar; Batlle, Xavier; Labarta, Amilcar

2007-01-01

We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromagnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loop shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Overlap functions computed from the spin configurations along the loops have been obtained to explain the origin and magnitude of these features microscopically

Further results on open-loop compensation of rate-dependent hysteresis in a magnetostrictive actuator with the Prandtl-Ishlinskii model

Science.gov (United States)

Al Janaideh, Mohammad; Aljanaideh, Omar

2018-05-01

Apart from the output-input hysteresis loops, the magnetostrictive actuators also exhibit asymmetry and saturation, particularly under moderate to large magnitude inputs and at relatively higher frequencies. Such nonlinear input-output characteristics could be effectively characterized by a rate-dependent Prandtl-Ishlinskii model in conjunction with a function of deadband operators. In this study, an inverse model is formulated to seek real-time compensation of rate-dependent and asymmetric hysteresis nonlinearities of a Terfenol-D magnetostrictive actuator. The inverse model is formulated with the inverse of the rate-dependent Prandtl-Ishlinskii model, satisfying the threshold dilation condition, with the inverse of the deadband function. The inverse model was subsequently applied to the hysteresis model as a feedforward compensator. The proposed compensator is applied as a feedforward compensator to the actuator hardware to study its potential for rate-dependent and asymmetric hysteresis loops. The experimental results are obtained under harmonic and complex harmonic inputs further revealed that the inverse compensator can substantially suppress the hysteresis and output asymmetry nonlinearities in the entire frequency range considered in the study.

Magnetoresistances in Ni80Fe20-ITO granular film

International Nuclear Information System (INIS)

Gao Chunhong; Chen Ke; Yang Yanxia; Xiong Yuanqiang; Chen Peng

2012-01-01

Highlights: ► Magnetoresistance (MR) in Ni 80 Fe 20 -ITO granular film are investigated. ► MR is positive at high temperature, and is negative at low temperature. ► MR results from the competition among three mechanisms. - Abstract: The magnetic properties, electrical properties and magnetoresistance are investigated in Ni 80 Fe 20 -ITO granular film with various volume fractions V NF of Ni 80 Fe 20 . The room temperature magnetization hysteresis of sample with V NF = 25% shows superparamagnetic behavior. Current-voltage curve of sample with V NF = 25% at 175 K shows typical tunneling-type behavior. The magnetoresistances of samples with low V NF are positive at high temperature, and are negative at low temperature. The temperature-dependent magnetoresistances result from the competition among ordinary magnetoresistances, the granular-typed tunneling magnetoresistance and the spin-mixing induced magnetoresistances.

Giant magnetoresistance of hysteresis-free Cu/Co-based multilayers

International Nuclear Information System (INIS)

Huetten, A.; Hempel, T.; Schepper, W.; Kleineberg, U.; Reiss, G.

2001-01-01

It has been demonstrated that hysteresis-free multilayers based on {Cu/Co} and {Cu/Ni 57 Co 43 } can be experimentally realized obtaining room temperature GMR effect amplitudes from 6.5% up to 20%. A critical window for the layer thickness for hysteresis-free GMR curves can be achieved for both systems, ranging from 0.38 to 0.45 nm and 0.59 to 0.7 nm, respectively. The corresponding sensitivities range from 0.075 up to 0.114%/Oe, but are still below that of normal {Cu/Co} multilayers. Hysteresis-free multilayers based on these systems are stable up to 180 deg. C upon isochronal annealing. It is shown that hysteresis-free {Cu/Co or Ni 57 Co 43 }-multilayers are neither a solution to achieve good temperature stability nor a higher sensitivity compared with normal ones and hence are not candidates for application

Physics behind the magnetic hysteresis loop--a survey of misconceptions in magnetism literature

International Nuclear Information System (INIS)

Sung, H.W.F.; Rudowicz, C.

2003-01-01

An extensive survey of misinterpretations and misconceptions concerning presentation of the hysteresis loop for ferromagnetic materials occurring in undergraduate textbooks has recently been carried out. As a follow-up, this article provides similar examples, now drawn from recent magnetism literature. The distinction between the two notions of 'coercivity' referred to the B vs. H curve and the M vs. H curve, which turn out to be often confused in textbooks is elucidated. Various misinterpretations and conceptual problems revealed by our survey of recent magnetism-related scientific journals are summarized. In order to counteract the misinterpretations in question, some real examples of hysteresis loops showing the correct characteristics have also been identified in this search. Various ways of presenting units for the same physical quantity, i.e. the SI or cgs units as well as both units mixed, have been revealed in the regular articles. This is a worrying factor, which calls for a concerted action at the level of the whole magnetism community. A number of intricacies and fundamental conceptual problems in magnetism encountered in a recent review are dealt with in a separate note

Magnetic vortex chirality determination via local hysteresis loops measurements with magnetic force microscopy

Science.gov (United States)

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Manzin, Alessandra; Vinai, Franco; Tiberto, Paola

2016-01-01

Magnetic vortex chirality in patterned square dots has been investigated by means of a field-dependent magnetic force microscopy technique that allows to measure local hysteresis loops. The chirality affects the two loop branches independently, giving rise to curves that have different shapes and symmetries as a function of the details of the magnetisation reversal process in the square dot, that is studied both experimentally and through micromagnetic simulations. The tip-sample interaction is taken into account numerically, and exploited experimentally, to influence the side of the square where nucleation of the vortex preferably occurs, therefore providing a way to both measure and drive chirality with the present technique. PMID:27426442

Magnetoresistance of nanogranular Ni/NiO controlled by exchange anisotropy

International Nuclear Information System (INIS)

Del Bianco, L.; Spizzo, F.; Tamisari, M.; Allia, P.

2013-01-01

A link between exchange anisotropy and magnetoresistance has been found to occur in a Ni/NiO sample consisting of Ni nanocrystallites (mean size ∼13 nm, Ni content ∼33 vol%) dispersed in a NiO matrix. This material shows metallic-type electric conduction and isotropic spin-dependent magnetoresistance as well as exchange bias effect. The latter is the outcome of an exchange anisotropy arising from the contact interaction between the Ni phase and the NiO matrix. Combined analysis of magnetization M(H) and magnetoresistance MR(H) loops measured in the 5–250 K temperature range after zero-field-cooling (ZFC) and after field-cooling (FC) from 300 K reveals that the magnetoresistance is influenced by exchange anisotropy, which is triggered by the FC process and can be modified in strength by varying the temperature. Compared to the ZFC case, the exchange anisotropy produces a horizontal shift of the FC MR(H) loop along with a reduction of the MR response associated to the reorientation of the Ni moments. A strict connection between magnetoresistance and remanent magnetization of FC loops on one side and the exchange field on the other, ruled by exchange anisotropy, is indicated. - Highlights: • Nanogranular Ni/NiO with giant magnetoresistance (MR) and exchange bias effect. • Exchange anisotropy produces a shift of the field-cooled MR(H) loop and reduces MR. • MR, remanence of field-cooled loops and exchange field are three correlated quantities. • It is possible to control MR of nanogranular systems through the exchange anisotropy

Effects of the amorphization on hysteresis loops of the amorphous spin-1/2 Ising system

International Nuclear Information System (INIS)

Essaoudi, I.; Ainane, A.; Saber, M.; Miguel, J.J. de

2009-01-01

We examine the effects of the amorphization on the hysteresis loops of the amorphous spin-1/2 Ising system using the effective field theory within a probability distribution technique that accounts for the self-spin correlation functions. The magnetization, the transverse and longitudinal susceptibilities, and pyromagnetic coefficient are also studied in detail

Nondestructive characterization of recovery and recrystallization in cold rolled low carbon steel by magnetic hysteresis loops

International Nuclear Information System (INIS)

Martinez-de-Guerenu, A.; Gurruchaga, K.; Arizti, F.

2007-01-01

How structure sensitive parameters derived from hysteresis loops can provide nondestructive information about the evolution of the microstructure of cold rolled low carbon steel as a result of recovery and recrystallization processes during the annealing is shown. The coercive field, remanent induction and hysteresis losses can be used to monitor the decrease in the dislocation density during recovery. These parameters are also influenced by the average grain refinement that takes place during recrystallization, which compensates the variation produced by the annihilation of dislocations during recrystallization. The maximum of the induction and of the relative differential permeability are shown to be very sensitive to the onset and to the monitoring of the recrystallization, respectively. The correlations between coercive field and remanent induction and hysteresis losses can also be used to distinguish between recovery and recrystallization

Study on the characteristics of hysteresis loop and resistance of glow discharge plasma using argon gas

Science.gov (United States)

Mathew, Prijil; Sajith Mathews, T.; Kurian, P. J.; Chattopadyay, P. K.

2018-05-01

Hysteresis in discharge current is produced in a low-pressure, magnetic field free, Glow discharge plasma by varying discharge voltage. The variation in area of the hysteresis loops with pressure, electrode distance and load resistor studied. To understand, the nonlinear behaviour of the I-V characteristics, the changes in gas resistance with electrode voltage, pressure and load resistor were studied. After many trials we propose the best suitable empirical equation for the exponential decrease of the gas resistance with electrode voltage as; R = Rmin + Ae-0.008V, which is a novel one and matches well with our experimental results.

Local hysteresis loops measurements on irradiated FeSiB patterned dots by magnetic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Coïsson, M., E-mail: m.coisson@inrim.it [INRIM, Electromagnetism Division, strada delle Cacce 91, 10135 Torino (Italy); Barrera, G. [INRIM, Electromagnetism Division, strada delle Cacce 91, 10135 Torino (Italy); Università di Torino, Dipartimento di Chimica, via P. Giuria 9, 10125 Torino (Italy); Celegato, F.; Enrico, E.; Olivetti, E.S.; Tiberto, P.; Vinai, F. [INRIM, Electromagnetism Division, strada delle Cacce 91, 10135 Torino (Italy)

2015-01-01

Magnetic Force Microscopy (MFM) has been exploited to develop a technique capable of investigating the field-dependent magnetisation reversal processes in patterned systems, allowing the full reconstruction of a local hysteresis loop. Fe–Si–B dots with a lateral size of 6μm and a thickness of 250 nm have been prepared by sputtering and optical lithography. In the as-prepared state, the dots are characterised by a dense stripe domain configuration, clearly visible at the MFM. Subsequently, the dots have been thinned by means of exposition to a focussed ion beam, consisting of Ga{sup +} ions having an energy of 30 keV. The local hysteresis loops have been measured by means of the MFM-derived technique. The progressive thinning of the dots results in the disappearance of the perpendicular anisotropy responsible for the dense stripe domain configuration, with the dominance of the shape anisotropy for thickness values below ≈70nm. The results are consistent with the spin reorientation transition effect studied on similar systems in the form of continuous thin films.

Local hysteresis loops measurements on irradiated FeSiB patterned dots by magnetic force microscopy

International Nuclear Information System (INIS)

Coïsson, M.; Barrera, G.; Celegato, F.; Enrico, E.; Olivetti, E.S.; Tiberto, P.; Vinai, F.

2015-01-01

Magnetic Force Microscopy (MFM) has been exploited to develop a technique capable of investigating the field-dependent magnetisation reversal processes in patterned systems, allowing the full reconstruction of a local hysteresis loop. Fe–Si–B dots with a lateral size of 6μm and a thickness of 250 nm have been prepared by sputtering and optical lithography. In the as-prepared state, the dots are characterised by a dense stripe domain configuration, clearly visible at the MFM. Subsequently, the dots have been thinned by means of exposition to a focussed ion beam, consisting of Ga + ions having an energy of 30 keV. The local hysteresis loops have been measured by means of the MFM-derived technique. The progressive thinning of the dots results in the disappearance of the perpendicular anisotropy responsible for the dense stripe domain configuration, with the dominance of the shape anisotropy for thickness values below ≈70nm. The results are consistent with the spin reorientation transition effect studied on similar systems in the form of continuous thin films

Study of vortex configurations in Yb3Rh4Sn13 via minor hysteresis loops

International Nuclear Information System (INIS)

Sarkar, S.; Tulapurkar, A.A.; Ramakrishnan, S.; Grover, A.K.; Tomy, C.V.

2001-01-01

The tracings of the minor hysteresis loops in the superconductor Yb 3 Rh 4 Sn 13 (i) elucidate the path dependence in J c (H), (ii) help to reach the stable vortex configuration from a given metastable state and (iii) reveal the occurrence of step change in equilibrium magnetization across the peak effect (PE) regime. (author)

3D and 1D calculation of hysteresis loops and energy products for anisotropic nanocomposite films with perpendicular anisotropy

International Nuclear Information System (INIS)

Yuan, X.H.; Zhao, G.P.; Yue, Ming; Ye, L.N.; Xia, J.; Zhang, X.C.; Chang, J.

2013-01-01

In this paper, the magnetic reversal process, hysteresis loops and energy products for exchange-coupled Nd 2 Fe 14 B/α-Fe bilayers are studied systematically by a three-dimensional (3D) model. The 3D calculations are numerically solved using the finite difference method, where the results are carefully compared with those calculated by one-dimensional (1D) model. It is found that the calculated hysteresis loops and energy products based on the two methods are consistent with each other. Both nucleation fields and coercivities decrease monotonically as the soft layer thickness L s increases. In addition, the calculated spatial distributions of magnetization orientations in the thickness direction at various applied fields based on both methods signify a three-step magnetic reversal process, which are nucleation, growth and displacement of the domain wall. The calculated magnetic orientations within the film plane, however, are totally different according to the two methods. The 3D calculation exhibits a process of vortex formation and annihilation. On the other hand, the 1D calculation gives a quasi-coherent one, where magnetization orientation is coherent in the film plane and varies in the thickness direction. This new reversal mechanism displayed in the film plane has a systematic influence on the nucleation fields, coercivity and energy products. - Highlights: • Consistent hysteresis loops and energy products for 3D and 1D calculation. • Domain wall formation, evolution and displacement perpendicular to the film plane. • Vortex formation, annihilation and better loop squareness in 3D calculation. • Larger nucleation fields, remanence and smaller coercivity in 3D calculation

Anomalous magnetoresistance effect in sputtered TbFeCo relating to dispersed magnetic moment

International Nuclear Information System (INIS)

Yumoto, S.; Toki, K.; Okada, O.; Gokan, H.

1988-01-01

The electric resistance is sputtered TbFeCo has been measured at room temperature as a function of magnetic field perpendicular to the film plane. Two kinds of anomalous magnetoresistance have been observed. One is a magnetoresistance peak in the magnetization reversal region. The other is reversible change proportional to the applied magnetic field, appearing in the other region. The magnetoresistance peak agrees well with a curve calculated from experimental Hall loop, using a phenomenological relation between anomalous magnetoresistance and anomalous Hall voltage. The magnetoresistance peak is found to originate from magnetic domain walls. The linear magnetoresistance change for TM dominant samples appears in a direction opposite to that for RE dominant samples. The linear change can't be derived from Hall loop

Study of magnetoresistance in the supercooled state of Dy-Y alloys

Science.gov (United States)

Jena, Rudra Prasad; Lakhani, Archana

2018-02-01

We report the magnetoresistance studies on Dy1-xYx (x ≤ 0.05) alloys across the first order helimagnetic to ferromagnetic phase transition. These alloys exhibit multiple magnetic phases on varying the temperature and magnetic field. The magnetoresistance studies in the hysteresis region shows irreversibility in forward and reverse field cycles. The resistivity values at zero field for these alloys after zero field cooling to the measurement temperatures, are different in both forward and reverse field cycles. The path dependence of magnetoresistance suggests the presence of helimagnetic phase as the supercooled metastable state which transforms to the stable ferromagnetic state on increasing the field. At high magnetic fields negative magnetoresistance following a linear dependence with field is observed which is attributed to the magnon scattering.

Designing Hysteresis with Dipolar Chains

Science.gov (United States)

Concha, Andrés; Aguayo, David; Mellado, Paula

2018-04-01

Materials that have hysteretic response to an external field are essential in modern information storage and processing technologies. A myriad of magnetization curves of several natural and artificial materials have previously been measured and each has found a particular mechanism that accounts for it. However, a phenomenological model that captures all the hysteresis loops and at the same time provides a simple way to design the magnetic response of a material while remaining minimal is missing. Here, we propose and experimentally demonstrate an elementary method to engineer hysteresis loops in metamaterials built out of dipolar chains. We show that by tuning the interactions of the system and its geometry we can shape the hysteresis loop which allows for the design of the softness of a magnetic material at will. Additionally, this mechanism allows for the control of the number of loops aimed to realize multiple-valued logic technologies. Our findings pave the way for the rational design of hysteretical responses in a variety of physical systems such as dipolar cold atoms, ferroelectrics, or artificial magnetic lattices, among others.

Magnetization configurations and hysteresis loops of small permalloy ellipses

International Nuclear Information System (INIS)

Schneider, M; Liszkowski, J; Rahm, M; Wegscheider, W; Weiss, D; Hoffmann, H; Zweck, J

2003-01-01

We investigated systematically the easy axis magnetization reversal of 20 nm thick permalloy ellipses with a fixed major axis of 1.47 μm and minor axes of 0.22-1.47 μm. Lorentz transmission electron microscopy was used to image the micromagnetic configurations during magnetization reversal. Hysteresis loops of single ellipses were recorded by means of micro-Hall magnetometry and could be traced back to certain reversal mechanisms observed by Lorentz microscopy. In most cases, the magnetization reversal is initiated by the evolution of a magnetization buckling, followed by the formation of a single, a double, or a trapped vortex configuration. For ellipses with high aspect ratio (length-to-width ratio), the magnetization switches in the reversed magnetic field without creation of a stable vortex configuration. Our experiments show that the characteristic field values for vortex creation, single vortex annihilation, and switching strongly depend on the shape anisotropy of the elements

Magnetic Biasing of a Ferroelectric Hysteresis Loop in a Multiferroic Orthoferrite

Science.gov (United States)

Tokunaga, Y.; Taguchi, Y.; Arima, T.; Tokura, Y.

2014-01-01

In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign.

Hysteresis compensation of piezoelectric deformable mirror based on Prandtl-Ishlinskii model

Science.gov (United States)

Ma, Jianqiang; Tian, Lei; Li, Yan; Yang, Zongfeng; Cui, Yuguo; Chu, Jiaru

2018-06-01

Hysteresis of piezoelectric deformable mirror (DM) reduces the closed-loop bandwidth and the open-loop correction accuracy of adaptive optics (AO) systems. In this work, a classical Prandtl-Ishlinskii (PI) model is employed to model the hysteresis behavior of a unimorph DM with 20 actuators. A modified control algorithm combined with the inverse PI model is developed for piezoelectric DMs. With the help of PI model, the hysteresis of the DM was reduced effectively from about 9% to 1%. Furthermore, open-loop regenerations of low-order aberrations with or without hysteresis compensation were carried out. The experimental results demonstrate that the regeneration accuracy with PI model compensation is significantly improved.

Inverse Magnetoresistance in Polymer Spin Valves.

Science.gov (United States)

Ding, Shuaishuai; Tian, Yuan; Li, Yang; Mi, Wenbo; Dong, Huanli; Zhang, Xiaotao; Hu, Wenping; Zhu, Daoben

2017-05-10

In this work, both negative and positive magnetoresistance (MR) in solution-processed regioregular poly(3-hexylthiophene) (RR-P3HT) is observed in organic spin valves (OSVs) with vertical La 2/3 Sr 1/3 MnO 3 (LSMO)/P3HT/AlO x /Co configuration. The ferromagnetic (FM) LSMO electrode with near-atomic flatness is fabricated by a DC facing-target magnetron sputtering method. This research is focused on the origin of the MR inversion. Two types of devices are investigated in details: One with Co penetration shows a negative MR of 0.2%, while the other well-defined device with a nonlinear behavior has a positive MR of 15.6%. The MR measurements in LSMO/AlO x /Co and LSMO/Co junctions are carried to exclude the interference of insulating layer and two FM electrodes themselves. By examining the Co thicknesses and their corresponding magnetic hysteresis loops, a spin-dependent hybrid-interface-state model by Co penetration is induced to explain the MR sign inversion. These results proven by density functional theory (DFT) calculations may shed light on the controllable interfacial properties in designing novel OSV devices.

Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

KAUST Repository

Xing, G. Z.

2014-05-23

We report the magnetic and magnetotransport properties of (In 0.985Nd0.015)2O2.89 thin films grown by pulse laser deposition. The clear magnetization hysteresis loops with the complementary magnetic domain structure reveal the intrinsic room temperature ferromagnetism in the as-prepared films. The strong sp-f exchange interaction as a result of the rare earth doping is discussed as the origin of the magnetotransport behaviours. A positive magnetoresistance (∼29.2%) was observed at 5 K and ascribed to the strong ferromagnetic sp-f exchange interaction in (In0.985Nd0.015)2O 2.89 thin films due to a large Zeeman splitting in an external magnetic field of 50 KOe. © 2014 AIP Publishing LLC.

Development of Digital Hysteresis Current Control with PLL Loop Gain Compensation Strategy for PWM Inverters with Constant Switching Frequency

Directory of Open Access Journals (Sweden)

N. Belhaouchet

2008-03-01

Full Text Available Hysteresis current control is one of the simplest techniques used to control the magnitude and phase angle of motor current for motor drives systems. However, this technique presents several disadvantages such as operation at variable switching frequency which can reveal problems of filtering, interference between the phases in the case of the three-phase systems with insulated neutral connection or delta connection, and irregularity of the modulation pulses which especially causes an acoustic noise on the level of the machine for the high power drive. In this paper, a new technique is proposed for a variable-hysteresis-band controller based on dead beat control applied to three phase voltage source PWM inverters feeding AC motors. Its main aim is firstly ensure a constant switching frequency and secondly the synchronization of modulation pulses using the phase-locked-loop with loop gain compensation in order to ensure a better stability. The behavior of the proposed technique is verified by simulation.

Magnetoresistance anomaly in DyFeCo thin films

International Nuclear Information System (INIS)

Wu, J. C.; Wu, C. S.; Wu, Te-ho; Chen, Bing-Mau; Shieh, Han-Ping D.

2001-01-01

Microstructured rare-earth - transition-metal DyFeCo films have been investigated using magnetoresistance and extraordinary Hall-effect measurements. The Hall loops reveal variation of coercive fields depending on the linewidth and the composition of the films. The magnetoresistance curves, with changes up to as high as 1.3%, show positive/negative magnetoresistance peaks centered on the coercive fields depending on the linewidth of the films only. The variation of the coercivity can be attributed to the magnetic moment canting between the Dy and FeCo subcomponents and the existence of the diverged magnetization on the edges, and the anomalous magnetoresistance peaks observed are discussed with the existing theories. [copyright] 2001 American Institute of Physics

Cumulative growth of minor hysteresis loops in the Kolmogorov model

International Nuclear Information System (INIS)

Meilikhov, E. Z.; Farzetdinova, R. M.

2013-01-01

The phenomenon of nonrepeatability of successive remagnetization cycles in Co/M (M = Pt, Pd, Au) multilayer film structures is explained in the framework of the Kolmogorov crystallization model. It is shown that this model of phase transitions can be adapted so as to adequately describe the process of magnetic relaxation in the indicated systems with “memory.” For this purpose, it is necessary to introduce some additional elements into the model, in particular, (i) to take into account the fact that every cycle starts from a state “inherited” from the preceding cycle and (ii) to assume that the rate of growth of a new magnetic phase depends on the cycle number. This modified model provides a quite satisfactory qualitative and quantitative description of all features of successive magnetic relaxation cycles in the system under consideration, including the surprising phenomenon of cumulative growth of minor hysteresis loops.

Exchange bias effect and intragranular magnetoresistance in Nd0.84Sr0.16CoO3

International Nuclear Information System (INIS)

Patra, M; Majumdar, S; Giri, S

2009-01-01

Electrical transport properties as a function of magnetic field and time have been investigated in polycrystalline, Nd 0.84 Sr 0.16 CoO 3 . A strong exchange bias (EB) effect is observed associated with the fairly large intragranular magnetoresistance (MR). The EB effect observed in the MR curve is compared with the EB effect manifested in the magnetic hysteresis loop. A training effect, described as the decrease of EB effect when the sample is successively field cycled at a particular temperature, has been observed in the shift of the MR curve. The training effect could be analyzed by successful models. The EB effect, MR and a considerable time dependence in MR are attributed to the intrinsic nanostructure giving rise to varieties of magnetic interfaces in the grain interior.

Open-loop magneto-resistance sensor-based DC current transformer for FAIR

Energy Technology Data Exchange (ETDEWEB)

Soliman, Eman; Hofmann, Klaus [Technical University Darmstadt (Germany); Reeg, Hansjoerg; Schwickert, Marcus [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany)

2016-07-01

A Novel DC Current Transformer (N-DCCT) is currently under development for FAIR. The N-DCCT is going to be installed inside the SIS100 synchrotron. The proposed system is no longer based on magnetic modulation principle of the conventional DCCT. Instead, a Magneto-resistance sensor is utilized to detect the magnetic field of the ion-beam. For a first prototype the N-DCCT is realized as an open-loop system. It consists of a high permeability slotted ring core and up to two MR sensors. The maximum ion-beam current magnetic field is concentrated inside the ring core air gaps. MR sensors are placed inside the core air gaps. The sensor output voltage is directly proportional to the ion-beam current. The system is implemented using commercial Tunneling MR sensors. Measurements using one single sensor, as well as the application of two sensors are presented in this work. The sensitivity of the proposed N-DCCT is 0.566 [V/A] for one single MR sensor and 1.56 [V/A] when two sensors are implemented.

Kerr hysteresis loop tracer with alternate driving magnetic field up to 10 kHz

Science.gov (United States)

Callegaro, Luca; Fiorini, Carlo; Triggiani, Giacomo; Puppin, Ezio

1997-07-01

A magneto-optical Kerr loop tracer for hysteresis loop measurements in thin films with field excitation frequency f0 from 10 mHz to 10 kHz is described. A very high sensitivity is obtained by using an ultrabright light-emitting diode as a low-noise light source and a novel acquisition process. The field is generated with a coil driven by an audio amplifier connected to a free-running oscillator. The conditioned detector output constitutes the magnetization signal (M); the magnetic field (H) is measured with a fast Hall probe. The acquisition electronics are based on a set of sample-and-hold amplifiers which allow the simultaneous sampling of M, H, and dH/dt. Acquisition is driven by a personal computer equipped with a multifunction I/O board. Test results on a 120 nm Fe film on Si substrate are shown. The coercive field of the film increases with frequency and nearly doubles at 10 kHz with respect to dc.

A simple model of hysteresis behavior using spreadsheet analysis

Science.gov (United States)

Ehrmann, A.; Blachowicz, T.

2015-01-01

Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.

A simple model of hysteresis behavior using spreadsheet analysis

International Nuclear Information System (INIS)

Ehrmann, A; Blachowicz, T

2015-01-01

Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur

Non-linear control of a hydraulic piezo-valve using a generalised Prandtl-Ishlinskii hysteresis model

Science.gov (United States)

Stefanski, Frederik; Minorowicz, Bartosz; Persson, Johan; Plummer, Andrew; Bowen, Chris

2017-01-01

The potential to actuate proportional flow control valves using piezoelectric ceramics or other smart materials has been investigated for a number of years. Although performance advantages compared to electromagnetic actuation have been demonstrated, a major obstacle has proven to be ferroelectric hysteresis, which is typically 20% for a piezoelectric actuator. In this paper, a detailed study of valve control methods incorporating hysteresis compensation is made for the first time. Experimental results are obtained from a novel spool valve actuated by a multi-layer piezoelectric ring bender. A generalised Prandtl-Ishlinskii model, fitted to experimental training data from the prototype valve, is used to model hysteresis empirically. This form of model is analytically invertible and is used to compensate for hysteresis in the prototype valve both open loop, and in several configurations of closed loop real time control system. The closed loop control configurations use PID (Proportional Integral Derivative) control with either the inverse hysteresis model in the forward path or in a command feedforward path. Performance is compared to both open and closed loop control without hysteresis compensation via step and frequency response results. Results show a significant improvement in accuracy and dynamic performance using hysteresis compensation in open loop, but where valve position feedback is available for closed loop control the improvements are smaller, and so conventional PID control may well be sufficient. It is concluded that the ability to combine state-of-the-art multi-layer piezoelectric bending actuators with either sophisticated hysteresis compensation or closed loop control provides a route for the creation of a new generation of high performance piezoelectric valves.

Double switching hysteresis loop in a single layer Fe3Pt alloy thin films

International Nuclear Information System (INIS)

Nahid, M.A.I.; Suzuki, Takao

2008-01-01

The Fe 3 Pt alloy thin films were epitaxially grown on MgO(100) substrate by e-beam evaporation. The films were partially ordered at the substrate deposition temperature above 350 deg. C. These partially ordered films exhibit very large biaxial magnetic anisotropy constant in the order of 10 5 J/m 3 and produce double switching in the hysteresis loops. The difference of the switching field of these films can be up to about 3 x 10 5 A/m by tuning the angle of the applied field with respect to the easy axes. This double switching behavior stems from the large biaxial magnetic anisotropy of the films

Criteria for saturated magnetization loop

International Nuclear Information System (INIS)

Harres, A.; Mikhov, M.; Skumryev, V.; Andrade, A.M.H. de; Schmidt, J.E.; Geshev, J.

2016-01-01

Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe_3O_4 and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one. - Highlights: • Proper estimation of hysteresis-loop parameters is vital in magnetic studies. • We propose criteria for discrimination minor from major hysteresis loops. • The criteria analyze magnetization, remanence and ZFC/FC curves and/or their derivatives. • Examples of their application on real nanoparticles systems are given. • Using the criteria could avoid twofold or bigger saturation-field underestimation errors.

Criteria for saturated magnetization loop

Energy Technology Data Exchange (ETDEWEB)

Harres, A. [Departamento de Física, UFSM, Santa Maria, 97105-900 Rio Grande do Sul (Brazil); Mikhov, M. [Faculty of Physics, University of Sofia, 1164 Sofia (Bulgaria); Skumryev, V. [Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona (Spain); Departament de Física, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Andrade, A.M.H. de; Schmidt, J.E. [Instituto de Física, UFRGS, Porto Alegre, 91501-970 Rio Grande do Sul (Brazil); Geshev, J., E-mail: julian@if.ufrgs.br [Departament de Física, Universitat Autònoma de Barcelona, 08193 Barcelona (Spain); Instituto de Física, UFRGS, Porto Alegre, 91501-970 Rio Grande do Sul (Brazil)

2016-03-15

Proper estimation of magnetization curve parameters is vital in studying magnetic systems. In the present article, criteria for discrimination non-saturated (minor) from saturated (major) hysteresis loops are proposed. These employ the analysis of (i) derivatives of both ascending and descending branches of the loop, (ii) remanent magnetization curves, and (iii) thermomagnetic curves. Computational simulations are used in order to demonstrate their validity. Examples illustrating the applicability of these criteria to well-known real systems, namely Fe{sub 3}O{sub 4} and Ni fine particles, are provided. We demonstrate that the anisotropy-field value estimated from a visual examination of an only apparently major hysteresis loop could be more than two times lower than the real one. - Highlights: • Proper estimation of hysteresis-loop parameters is vital in magnetic studies. • We propose criteria for discrimination minor from major hysteresis loops. • The criteria analyze magnetization, remanence and ZFC/FC curves and/or their derivatives. • Examples of their application on real nanoparticles systems are given. • Using the criteria could avoid twofold or bigger saturation-field underestimation errors.

Compensator design for hysteresis of a stacked PZT actuator using a congruency-based hysteresis model

International Nuclear Information System (INIS)

Nguyen, Phuong-Bac; Choi, Seung-Bok

2012-01-01

This paper proposes a rate-independent hysteresis compensator for a stacked PZT (lead zirconate titanate) actuator. From a congruency-based hysteresis (CBH) model which is derived from the inherent properties of this actuator, especially the congruency, a feedforward compensator associated with it is developed. The formulation of the proposed compensator is based on an assumption that the inverse operator also possesses the same properties as the CBH model does. This implies that the compensator also possesses properties such as the wiped-out loop closing between the consecutive control points and congruency. Consequently, the expressions for the compensator can be conducted by exploiting the equations for the CBH model in two cases of monotonic increase and monotonic decrease of input excitation. In order to assess the performance of the compensator, several experiments in both open-loop and closed-loop controls are undertaken. In the open-loop control experiment, the performance of the feedforward compensator using the CBH model is compared with the classical Preisach model-based one in three cases of reference waveforms. In the closed-loop control experiment, the proposed compensator is incorporated into a PID (proportional-integral-derivative) control system and the performance of this integrated system is then evaluated and compared to that of the PID with and without compensator. (paper)

Giant magnetoresistance associated with a first-order transition between two ferrimagnetic states in Mn2-xZnxSb (x < 0.3) compounds

International Nuclear Information System (INIS)

Zhang, Q; Zhang, Y Q; Li, Y B; Du, J; Feng, W J; Li, D; Zhang, Z D

2008-01-01

A giant magnetoresistance (GMR) is observed in the Mn 2-x Zn x Sb (x 1.9 Zn 0.1 Sb compound. Different from other Mn 2 Sb-based compounds, the GMR in Mn 2-x Zn x Sb is closely correlated with a field-induced transition from a weak ferrimagnetic (WFI) state to a ferrimagnetic (FI) state. It is understood that the influences of both super-zone gap and spin-dependent scattering are responsible for GMR in the present system. Magnetic hysteresis and phase coexistence of the WFI and the FI phases suggest that this WFI-FI transition is of first order. The different mechanisms responsible for butterfly loops of magnetization/resistivity curves in different magnetic states are discussed

Mathematical modelling of frequency-dependent hysteresis and energy loss of FeBSiC amorphous alloy

International Nuclear Information System (INIS)

Koprivica, Branko; Milovanovic, Alenka; Mitrovic, Nebojsa

2017-01-01

The aim of this paper is to present a novel mathematical model of frequency-dependent magnetic hysteresis. The major hysteresis loop in this model is represented by the ascending and descending curve over an arctangent function. The parameters of the hysteresis model have been calculated from a measured hysteresis loop of the FeBSiC amorphous alloy sample. A number of measurements have been performed with this sample at different frequencies of the sinusoidal excitation magnetic field. A variation of the coercive magnetic field with the frequency has been observed and used in the modelling of frequency-dependent hysteresis with the proposed model. A comparison between measured and modelled hysteresis loops has been presented. Additionally, the areas of the obtained hysteresis loops, representing the energy loss per unit volume, have been calculated and the dependence of the energy loss on the frequency is shown. Furthermore, two models of the frequency dependence of the coercivity and two models of the energy loss separation have been used for fitting the experimental and simulation results. The relations between these models and their parameters have been observed and analysed. Also, the relations between parameters of the hysteresis model and the parameters of the energy loss separation models have been analysed and discussed. - Highlights: • A mathematical model of frequency-dependent hysteresis is proposed. • Dependence of coercivity and energy loss per unit volume on frequency is modelled. • Equivalence between models and relation between model parameters are presented.

A device model framework for magnetoresistive sensors based on the Stoner–Wohlfarth model

International Nuclear Information System (INIS)

Bruckner, Florian; Bergmair, Bernhard; Brueckl, Hubert; Palmesi, Pietro; Buder, Anton; Satz, Armin; Suess, Dieter

2015-01-01

The Stoner–Wohlfarth (SW) model provides an efficient analytical model to describe the behavior of magnetic layers within magnetoresistive sensors. Combined with a proper description of magneto-resistivity an efficient device model can be derived, which is necessary for an optimal electric circuit design. Parameters of the model are determined by global optimization of an application specific cost function which contains measured resistances for different applied fields. Several application cases are examined and used for validation of the device model. - Highlights: • An efficient device model framework for various types of magnetoresistive sensors is presented. • The model is based on the analytical solution of the Stoner–Wohlfarth model. • Numerical optimization methods provide optimal model parameters for a different application cases. • The model is applied to several application cases and is able to reproduce measured hysteresis and swiching behavior

Anisotropy of magnetoresistance on trapping magnetic fields in granular HTSC

CERN Document Server

Sukhanov, A A

2003-01-01

The features of magnetoresistance in Bi (Pb)-HTSC ceramics with the magnetic fields trapped are investigated. It is found that on trapping magnetic flux the magnetoresistance in granular HTSC becomes anisotropic. Moreover, for magnetic fields H parallel and currents perpendicular to field H sub i which induces the trapping the magnetoresistance field dependence DELTA R(H) is nonmonotonic and the magnetoresistance is negative for small fields H < Hinv. The effect of trapped field and transport current and their orientations on the dependence DELTA R(H) is investigated. In particular, it is found that the field of magnetoresistance sign inversion Hinv almost linearly grows with increase of the effective trapped magnetic fields. Hinv decreases down to zero as the angle between fields H and H sub i increases up to pi/2 and slightly decreases with increasing transport current. The results are treated in terms of the model of magnetic flux trapping in superconducting grains or 'loops' embedded in a matrix of wea...

Lift hysteresis at stall as an unsteady boundary-layer phenomenon

Science.gov (United States)

Moore, Franklin K

1956-01-01

Analysis of rotating stall of compressor blade rows requires specification of a dynamic lift curve for the airfoil section at or near stall, presumably including the effect of lift hysteresis. Consideration of the magnus lift of a rotating cylinder suggests performing an unsteady boundary-layer calculation to find the movement of the separation points of an airfoil fixed in a stream of variable incidence. The consideration of the shedding of vorticity into the wake should yield an estimate of lift increment proportional to time rate of change of angle of attack. This increment is the amplitude of the hysteresis loop. An approximate analysis is carried out according to the foregoing ideas for a 6:1 elliptic airfoil at the angle of attack for maximum lift. The assumptions of small perturbations from maximum lift are made, permitting neglect of distributed vorticity in the wake. The calculated hysteresis loop is counterclockwise. Finally, a discussion of the forms of hysteresis loops is presented; and, for small reduced frequency of oscillation, it is concluded that the concept of a viscous "time lag" is appropriate only for harmonic variations of angle of attack with time at mean conditions other than maximum lift.

CALCULATION OF DESORPTION BRANCH OF HYSTERESIS LOOP TOR THE ADSORBENTS OF CORPUSCULAR STRUCTURE ON THE BASIS OF MODEL OF CYLINDRICAL PORES

Directory of Open Access Journals (Sweden)

V. V. Kutarov

2015-02-01

Full Text Available The method of calculation of desorption branch of hysteresis loop for the adsorbents of corpus­cular structure is offered. The method is based on the model of cylindrical pores. Applicability of equation is tested by a way comparing of calculation results to information, certain on experimental isotherms, on the example of two adsorption systems with different adsorbents and adsorbats

Frozen magnetoresistance at magnetization reversal of granular Bi(Pb)-HTSC

International Nuclear Information System (INIS)

Sukhanov, A.A.; Omelchenko, V.I.

2004-01-01

The frozen magnetoresistance dependences of granular Bi(Pb)-HTSC samples on fields initiating a magnetic flux trapping and on magnetic reversal fields Rt(Hi, Hr) are investigated. It is found that the Rt (Hr) dependences are nonmonotonous. The frozen magnetoresistance decreases substantially after the first pulse Hr applied (Hr < Hi) but remains practically unchanged at subsequent remagnetization by magnetic pulses of alternating polarity and of the same amplitude. The effect of magnetic reversal on magnetoresistance anisotropy and the negative magnetoresistance phenomenon are studied. Is shown that the results obtained are inconsistent with the model of critical state for SC grains and the model of SC loops but are well described quantitatively by the proposed Bi(Pb)-HTSC model according to which the magnetic flux trapping occurs in normal grains with HTSC shells and the sample resistance is determined by weak link chains

Hysteresis losses in a dense superparamagnetic nanoparticle assembly

Directory of Open Access Journals (Sweden)

S. A. Gudoshnikov

2012-03-01

Full Text Available The hysteresis losses of a dense assembly of magnetite nanoparticles with an average diameter D = 25 nm are measured in the frequency range f = 10 – 200 kHz for magnetic field amplitudes up to H0 = 400 Oe. The low frequency hysteresis loops of the assembly are obtained by means of integration of the electro-motive force signal arising in a small pick-up coil wrapped around a sample which contains 1 – 5 mg of a magnetite powder. It is proved experimentally that the specific absorption rate diminishes approximately 4.5 times when the sample aspect ratio decreases from 11.4 to 1. Theoretical estimate shows that experimentally measured hysteresis loops can be approximately described only by taking into account appreciable contributions of magnetic nanoparticles of both very small, D 30 nm, diameters. Thus the wide particle size distribution has to be assumed.

Simulation of magnetic hysteresis loops and magnetic Barkhausen noise of α-iron containing nonmagnetic particles

International Nuclear Information System (INIS)

Li, Yi; Li, Qiulin; Liu, Wei; Xu, Ben; Hu, Shenyang; Li, Yulan

2015-01-01

The magnetic hysteresis loops and Barkhausen noise of a single α-iron with nonmagnetic particles are simulated to investigate into the magnetic hardening due to Cu-rich precipitates in irradiated reactor pressure vessel (RPV) steels. Phase field method basing Landau-Lifshitz-Gilbert (LLG) equation is used for this simulation. The results show that the presence of the nonmagnetic particle could result in magnetic hardening by making the nucleation of reversed domains difficult. The coercive field is found to increase, while the intensity of Barkhausen noise voltage is decreased when the nonmagnetic particle is introduced. Simulations demonstrate the impact of nucleation field of reversed domains on the magnetization reversal behavior and the magnetic properties

A Novel Hysteresis Model of Magnetic Field Strength Determined by Magnetic Induction Intensity for Fe-3% Si Electrical Steel Applied in Cigarette Making Machines

Directory of Open Access Journals (Sweden)

Hao Wang

2016-01-01

Full Text Available Hysteresis characteristics of grain-oriented electrical steel were studied through the hysteresis loop. Existing hysteresis fitting simulation methods were summarized, and new Fe-3% Si grain-oriented electrical steel hysteresis loop model was proposed. Undetermined coefficients of the magnetic field intensity and magnetic flux density were determined by both the fixed angle method and the least squares method, and the hysteresis loop model was validated with high fitting degree by experimental data.

Constricted double loop hysteresis and exchange bias attributed to the surface anisotropy in nanocrystalline La1/3Sr2/3Fe1−xCrxO3

International Nuclear Information System (INIS)

Sabyasachi, Sk.; Patra, M.; Majumdar, S.; Giri, S.

2013-01-01

We investigate magnetic properties of nanocrystalline ferrites with composition La 1/3 Sr 2/3 Fe 1−x Cr x O 3 (LSFCO) for x=0, 0.02, 0.04 and 0.06. Thermal variation of zero field cooled magnetization displays a weak signature close to the charge (T CO ) as well as antiferromagnetic ordering for x=0, 0.02 and 0.04. In addition, another disordered glassy magnetic transition (T g ) is noticed for all the compositions. T g is predominantly observed, although signature of charge ordering almost disappears for x=0.06. Interestingly, a constricted double loop type magnetic hysteresis loop is observed for x=0.02. This structure in the hysteresis loop disappears with further increase in Cr substitution. A systematic shift in the magnetic hysteresis loop is observed for all the compositions, while samples are cooled in a static magnetic field, which is the manifestation of exchange bias (EB) effect. The EB field (H E ) and magnetization (M E ) decrease remarkably due to minor Cr substitution at x=0.02 and then it reveals a sluggish increase with increasing x. For x=0.04 the EB effect emerges below ∼T CO , increases sluggishly with lowering of temperature and below ∼T g , it increases rapidly. The cooling field dependence exhibits significant increase of H E and M E for x=0.04, which is associated with the considerable increase of coercivity. Possible origin of EB correlated with the magnetic phase coexistence has been argued for nanocrystalline LSFCO. - Highlights: • Constricted double loop structure is observed for minor Cr substitution. • Exchange bias decreases significantly due to Cr substitution. • Intricate magnetic phase coexistence leads to the exchange bias effect

Negative Charge Neutralization in the Loops and Turns of Outer Membrane Phospholipase A Impacts Folding Hysteresis at Neutral pH.

Science.gov (United States)

McDonald, Sarah K; Fleming, Karen G

2016-11-08

Hysteresis in equilibrium protein folding titrations is an experimental barrier that must be overcome to extract meaningful thermodynamic quantities. Traditional approaches to solving this problem involve testing a spectrum of solution conditions to find ones that achieve path independence. Through this procedure, a specific pH of 3.8 was required to achieve path independence for the water-to-bilayer equilibrium folding of outer membrane protein OmpLA. We hypothesized that the neutralization of negatively charged side chains (Asp and Glu) at pH 3.8 could be the physical basis for path-independent folding at this pH. To test this idea, we engineered variants of OmpLA with Asp → Asn and Glu → Gln mutations to neutralize the negative charges within various regions of the protein and tested for reversible folding at neutral pH. Although not fully resolved, our results show that these mutations in the periplasmic turns and extracellular loops are responsible for 60% of the hysteresis in wild-type folding. Overall, our study suggests that negative charges impact the folding hysteresis in outer membrane proteins and their neutralization may aid in protein engineering applications.

Hysteresis losses and specific absorption rate measurements in magnetic nanoparticles for hyperthermia applications.

Science.gov (United States)

Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Martino, Luca; Kane, Shashank N; Raghuvanshi, Saroj; Vinai, Franco; Tiberto, Paola

2017-06-01

Magnetic hysteresis loops areas and hyperthermia on magnetic nanoparticles have been studied with the aim of providing reliable and reproducible methods of measuring the specific absorption rate (SAR). The SAR of Fe 3 O 4 nanoparticles with two different mean sizes, and Ni 1-x Zn x Fe 2 O 4 ferrites with 0 ≤ x ≤ 0.8 has been measured with three approaches: static hysteresis loops areas, dynamic hysteresis loops areas and hyperthermia of a water solution. For dynamic loops and thermometric measurements, specific experimental setups have been developed, that operate at comparable frequencies (≈ 69kHz and ≈ 100kHz respectively) and rf magnetic field peak values (up to 100mT). The hyperthermia setup has been fully modelled to provide a direct measurement of the SAR of the magnetic nanoparticles by taking into account the heat exchange with the surrounding environment in non-adiabatic conditions and the parasitic heating of the water due to ionic currents. Dynamic hysteresis loops are shown to provide an accurate determination of the SAR except for superparamagnetic samples, where the boundary with a blocked regime could be crossed in dynamic conditions. Static hysteresis loops consistently underestimate the specific absorption rate but can be used to select the most promising samples. A means of reliably measure SAR of magnetic nanoparticles by different approaches for hyperthermia applications is presented and its validity discussed by comparing different methods. This work fits within the general subject of metrological traceability in medicine with a specific focus on magnetic hyperthermia. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader. Copyright © 2016 Elsevier B.V. All rights reserved.

Modeling the hysteresis of a scanning probe microscope

DEFF Research Database (Denmark)

Dirscherl, Kai; Garnæs, Jørgen; Nielsen, L.

2000-01-01

Most scanning probe microscopes use piezoelectric actuators in open loop configurations. Therefore a major problem related to these instruments is the image distortion due to the hysteresis effect of the piezo. In order to eliminate the distortions, cost effective software control based on a model...... for hysteresis can be applied to the scanner. We describe a new rate-independent model for the hysteresis of a piezo scanner. Two reference standards were used to determine the accuracy of the model; a one-dimensional grating with a period of 3.0 mum and a two-dimensional grating with 200 nm pitch...

Size dependent thermal hysteresis in spin crossover nanoparticles reflected within a Monte Carlo based Ising-like model

International Nuclear Information System (INIS)

Atitoaie, Alexandru; Tanasa, Radu; Enachescu, Cristian

2012-01-01

Spin crossover compounds are photo-magnetic bistable molecular magnets with two states in thermodynamic competition: the diamagnetic low-spin state and paramagnetic high-spin state. The thermal transition between the two states is often accompanied by a wide hysteresis, premise for possible application of these materials as recording media. In this paper we study the influence of the system's size on the thermal hysteresis loops using Monte Carlo simulations based on an Arrhenius dynamics applied for an Ising like model with long- and short-range interactions. We show that using appropriate boundary conditions it is possible to reproduce both the drop of hysteresis width with decreasing particle size, the hysteresis shift towards lower temperatures and the incomplete transition, as in the available experimental data. The case of larger systems composed by several sublattices is equally treated reproducing the shrinkage of the hysteresis loop's width experimentally observed. - Highlights: ► A study concerning size effects in spin crossover nanoparticles hysteresis is presented. ► An Ising like model with short- and long-range interactions and Arrhenius dynamics is employed. ► In open boundary system the hysteresis width decreases with particle size. ► With appropriate environment, hysteresis loop is shifted towards lower temperature and transition is incomplete.

Mathematical models of hysteresis

International Nuclear Information System (INIS)

1998-01-01

The ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema (not the entire input variations) leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. The origin of such tools can be traced back to the landmark paper of Preisach. Their research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. During the past four years, the study has been by and large centered around the following topics: (1) further development of Scalar and vector Preisach-type models of hysteresis; (2) experimental testing of Preisach-type models of hysteresis; (3) development of new models for viscosity (aftereffect) in hysteretic systems; (4) development of mathematical models for superconducting hysteresis in the case of gradual resistive transitions; (5) software implementation of Preisach-type models of hysteresis; and (6) development of new ideas which have emerged in the course of the research work. The author briefly describes the main scientific results obtained in the areas outlined above

Mathematical models of hysteresis

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-08-01

The ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema (not the entire input variations) leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. The origin of such tools can be traced back to the landmark paper of Preisach. Their research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. During the past four years, the study has been by and large centered around the following topics: (1) further development of Scalar and vector Preisach-type models of hysteresis; (2) experimental testing of Preisach-type models of hysteresis; (3) development of new models for viscosity (aftereffect) in hysteretic systems; (4) development of mathematical models for superconducting hysteresis in the case of gradual resistive transitions; (5) software implementation of Preisach-type models of hysteresis; and (6) development of new ideas which have emerged in the course of the research work. The author briefly describes the main scientific results obtained in the areas outlined above.

A RSM-based predictive model to characterize heat treating parameters of D2 steel using combined Barkhausen noise and hysteresis loop methods

Science.gov (United States)

Kahrobaee, Saeed; Hejazi, Taha-Hossein

2017-07-01

Austenitizing and tempering temperatures are the effective characteristics in heat treating process of AISI D2 tool steel. Therefore, controlling them enables the heat treatment process to be designed more accurately which results in more balanced mechanical properties. The aim of this work is to develop a multiresponse predictive model that enables finding these characteristics based on nondestructive tests by a set of parameters of the magnetic Barkhausen noise technique and hysteresis loop method. To produce various microstructural changes, identical specimens from the AISI D2 steel sheet were austenitized in the range 1025-1130 °C, for 30 min, oil-quenched and finally tempered at various temperatures between 200 °C and 650 °C. A set of nondestructive data have been gathered based on general factorial design of experiments and used for training and testing the multiple response surface model. Finally, an optimization model has been proposed to achieve minimal error prediction. Results revealed that applying Barkhausen and hysteresis loop methods, simultaneously, coupling to the multiresponse model, has a potential to be used as a reliable and accurate nondestructive tool for predicting austenitizing and tempering temperatures (which, in turn, led to characterizing the microstructural changes) of the parts with unknown heat treating conditions.

THE INFLUENCE OF HYSTERESIS IN CONSUMER’S BEHAVIOUR FOR PREMIUM PRICE EVALUATION

Directory of Open Access Journals (Sweden)

Evgeny KRYUKOV

2014-10-01

Full Text Available The paper deals with an example of the manifestation of the hysteresis in consumers’ behaviour for the Latvian company operating on the market closest to oligopoly and having a local brand name. Based on the quota sample of 332 company stores consumers, their loyalty, willingness to pay for domestic cosmetic products and the propensity to buy habitual products were evaluated. In the survey the unfolding bracketing procedure is used. It is shown that the relationship between the number of loyal consumers and the product price depends on the price increase or decrease and has the form of a hysteresis loop. The width of the hysteresis loop depends on the pricing of a competing company. The range of the premium prices bringing a positive economic impact is determined. The obtained results confirm a considerable influence of the hysteresis effect on consumers’ sensitivity to price changes. The findings can be useful for managers in evaluating a possible revenue growth connected with the premium pricing strategy.

Effects of V2O3 buffer layers on sputtered VO2 smart windows: Improved thermochromic properties, tunable width of hysteresis loops and enhanced durability

Science.gov (United States)

Long, Shiwei; Cao, Xun; Sun, Guangyao; Li, Ning; Chang, Tianci; Shao, Zewei; Jin, Ping

2018-05-01

Vanadium dioxide (VO2) is one of the most well-known thermochromic materials, which exhibits a notable optical change from transparent to reflecting in the infrared region upon a metal-insulator phase transition. For practical applications, VO2 thin films should be in high crystalline quality to obtain a strong solar modulation ability (ΔTsol). Meanwhile, narrow hysteresis loops and robust ambient durability are also indispensable for sensitivity and long-lived utilization, respectively. In this work, a series of high-quality V2O3/VO2 bilayer structures were grown on quartz glass substrates by reactive magnetron sputtering. Basically, the bottom V2O3 acts as the buffer layer to improve the crystallinity of the top VO2, while the VO2 serves as the thermochromic layer to guarantee the solar modulation ability for energy-saving. We observed an obvious increase in ΔTsol of 76% (from 7.5% to 13.2%) for VO2 films after introducing V2O3 buffer layers. Simultaneously, a remarkable reduction by 79% (from 21.9 °C to 4.7 °C) in width of hysteresis loop was obtained when embedding 60 nm V2O3 buffer for 60 nm VO2. In addition, VO2 with non-stoichiometry of V2O3±x buffer demonstrates a broadening hysteresis loops width, which is derived from the lattice distortion caused by lattice imperfection. Finally, durability of VO2 has been significantly improved due to positive effects of V2O3 buffer layer. Our results lead to a comprehensive enhancement in crystallinity of VO2 and shed new light on the promotion of thermochromic property by homologous oxides for VO2.

Percolative Theory of Organic Magnetoresistance and Fringe-Field Magnetoresistance

Science.gov (United States)

Flatté, Michael E.

2013-03-01

A recently-introduced percolation theory for spin transport and magnetoresistance in organic semiconductors describes the effects of spin dynamics on hopping transport by considering changes in the effective density of hopping sites, a key quantity determining the properties of percolative transport. Increases in the spin-flip rate open up ``spin-blocked'' pathways to become viable conduction channels and hence, as the spin-flip rate changes with magnetic field, produce magnetoresistance. Features of this percolative magnetoresistance can be found analytically in several regimes, and agree with measurements of the shape and saturation of measured magnetoresistance curves. We find that the threshold hopping distance is analogous to the branching parameter of a phenomenological two-site model, and that the distinction between slow and fast hopping is contingent on the threshold hopping distance. Regimes of slow and fast hopping magnetoresistance are uniquely characterized by their line shapes. Studies of magnetoresistance in known systems with controllable positional disorder would provide an additional stringent test of this theory. Extensions to this theory also describe fringe-field magnetoresistance, which is the influence of fringe magnetic fields from a nearby unsaturated magnetic electrode on the conductance of an organic film. This theory agrees with several key features of the experimental fringe-field magnetoresistance, including the applied fields where the magnetoresistance reaches extrema, the applied field range of large magnetoresistance effects from the fringe fields, and the sign of the effect. All work done in collaboration with N. J. Harmon, and fringe-field magnetoresistance work in collaboration also with F. Macià, F. Wang, M. Wohlgenannt and A. D. Kent. This work was supported by an ARO MURI.

Hysteresis responses of evapotranspiration to meteorological factors at a diel timescale: patterns and causes.

Directory of Open Access Journals (Sweden)

Han Zheng

Full Text Available Evapotranspiration (ET is an important component of the water cycle in terrestrial ecosystems. Understanding the ways in which ET changes with meteorological factors is central to a better understanding of ecological and hydrological processes. In this study, we used eddy covariance measurements of ET from a typical alpine shrubland meadow ecosystem in China to investigate the hysteresis response of ET to environmental variables including air temperature (Ta, vapor pressure deficit (VPD and net radiation (Rn at a diel timescale. Meanwhile, the simulated ET by Priestly-Taylor equation was used to interpret the measured ET under well-watered conditions. Pronounced hysteresis was observed in both Ta and VPD response curves of ET. At a similar Ta and VPD, ET was always significantly depressed in the afternoon compared with the morning. But the hysteresis response of ET to Rn was not evident. Similar hysteresis patterns were also observed in the Ta/VPD response curves of simulated ET. The magnitudes of the measured and simulated hysteresis loops showed similar seasonal variation, with relatively smaller values occurring from May to September, which agreed well with the lifetime of plants and the period of rainy season at this site. About 62% and 23% of changes in the strength of measured ET-Ta and ET-VPD loops could be explained by the changes in the strength of simulated loops, respectively. Thus, the time lag between Rn and Ta/VPD is the most important factor generating and modulating the ET-Ta/VPD hysteresis, but plants and water status also contribute to the hysteresis response of ET. Our research confirmed the different hysteresis in the responses of ET to meteorological factors and proved the vital role of Rn in driving the diel course of ET.

Molecular mechanism of adsorption/desorption hysteresis: dynamics of shale gas in nanopores

Science.gov (United States)

Chen, Jie; Wang, FengChao; Liu, He; Wu, HengAn

2017-01-01

Understanding the adsorption and desorption behavior of methane has received considerable attention since it is one of the crucial aspects of the exploitation of shale gas. Unexpectedly, obvious hysteresis is observed from the ideally reversible physical sorption of methane in some experiments. However, the underlying mechanism still remains an open problem. In this study, Monte Carlo (MC) and molecular dynamics (MD) simulations are carried out to explore the molecular mechanisms of adsorption/desorption hysteresis. First, a detailed analysis about the capillary condensation of methane in micropores is presented. The influence of pore width, surface strength, and temperature on the hysteresis loop is further investigated. It is found that a disappearance of hysteresis occurs above a temperature threshold. Combined with the phase diagram of methane, we explicitly point out that capillary condensation is inapplicable for the hysteresis of shale gas under normal temperature conditions. Second, a new mechanism, variation of pore throat size, is proposed and studied. For methane to pass through the throat, a certain energy is required due to the repulsive interaction. The required energy increases with shrinkage of the throat, such that the originally adsorbed methane cannot escape through the narrowed throat. These trapped methane molecules account for the hysteresis. Furthermore, the hysteresis loop is found to increase with the increasing pressure and decreasing temperature. We suggest that the variation of pore throat size can explain the adsorption/desorption hysteresis of shale gas. Our conclusions and findings are of great significance for guiding the efficient exploitation of shale gas.

submitter Hysteresis Losses and Effective $J_{c}(B)$ Scaling Law for ITER Nb$_{3}$Sn Strands

CERN Document Server

Seiler, E; Bordini, B; Bottura, L; Bessette, D; Vostner, A; Devred, A

2016-01-01

Hysteresis losses of five Nb$_{3}$Sn International Thermonuclear Experimental Reactor reference strands were investigated by means of magnetization loop measurements in a vibrating sample magnetometer in a perpendicularly applied magnetic field. The magnetization loops were recorded while continuously sweeping the applied field between the extreme values $±B_m$, covering a wide range of maximum applied fields (0.2-10 T). In this paper, we compare the directly determined hysteresis losses based on the area of the smaller measured loops and the losses calculated by the integration of the width ΔM of the $B_m$ = 10 T magnetization loop. A suitable fitting function is proposed to describe the ΔM(B) dependence, which leads, for each strand, to an excellent agreement with the experimentally determined hysteresis losses, magnetization, and pinning force. Transport critical current measurements in a perpendicularly applied magnetic field were also performed for all the strands, and on the basis of the comparison w...

Low-field microwave absorption and magnetoresistance in iron nanostructures grown by electrodeposition on n-type lightly doped silicon substrates

Energy Technology Data Exchange (ETDEWEB)

Felix, J.F. [Universidade Federal de Viçosa-UFV, Departamento de Física, 36570-900 Viçosa, MG (Brazil); Universidade de Brasília-UnB, Instituto de Física, Núcleo de Física Aplicada, 70910-900 Brasília, DF (Brazil); Figueiredo, L.C. [Universidade de Brasília-UnB, Instituto de Física, Núcleo de Física Aplicada, 70910-900 Brasília, DF (Brazil); Mendes, J.B.S. [Universidade Federal de Viçosa-UFV, Departamento de Física, 36570-900 Viçosa, MG (Brazil); Morais, P.C. [Universidade de Brasília-UnB, Instituto de Física, Núcleo de Física Aplicada, 70910-900 Brasília, DF (Brazil); Huazhong University of Science and Technology, School of Automation, 430074 Wuhan (China); Araujo, C.I.L. de., E-mail: dearaujo@ufv.br [Universidade de Brasília-UnB, Instituto de Física, Núcleo de Física Aplicada, 70910-900 Brasília, DF (Brazil)

2015-12-01

In this study we investigate magnetic properties, surface morphology and crystal structure in iron nanoclusters electrodeposited on lightly doped (100) n-type silicon substrates. Our goal is to investigate the spin injection and detection in the Fe/Si lateral structures. The samples obtained under electric percolation were characterized by magnetoresistive and magnetic resonance measurements with cycling the sweeping applied field in order to understand the spin dynamics in the as-produced samples. The observed hysteresis in the magnetic resonance spectra, plus the presence of a broad peak in the non-saturated regime confirming the low field microwave absorption (LFMA), were correlated to the peaks and slopes found in the magnetoresistance curves. The results suggest long range spin injection and detection in low resistive silicon and the magnetic resonance technique is herein introduced as a promising tool for analysis of electric contactless magnetoresistive samples. - Highlights: • Electrodeposition of Fe nanostructures on high resistive silicon substrates. • Spin polarized current among clusters through Si suggested by isotropic magnetoresistance. • Low field microwave absorption arising from the sample shape anisotropy. • Contactless magnetoresistive device characterization by resonance measurements.

Fourier transform and controlling of flux in scalar hysteresis measurement

International Nuclear Information System (INIS)

Kuczmann, Miklos

2008-01-01

The paper deals with a possible realization of eliminating the effect of noise in scalar hysteresis measurements. The measured signals have been transformed into the frequency domain, and, after applying digital filter, the spectrums of the filtered signals have been transformed back to the time domain. The proposed technique results in an accurate noise-removal algorithm. The paper illustrates a fast controlling algorithm applying the inverse of the actually measured hysteresis loop, and another proportional one to measure distorted flux pattern. By developing the mentioned algorithms, it aims at the controlling of a more complicated phenomena, i.e. measuring the vector hysteresis characteristics

Contact Angle Hysteresis on Graphene Surfaces and Hysteresis-free Behavior on Oil-infused Graphite Surfaces

Energy Technology Data Exchange (ETDEWEB)

Wu, Cyuan-Jhang; Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Woon, Wei-Yen [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Sheng, Yu-Jane, E-mail: yjsheng@ntu.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Tsao, Heng-Kwong, E-mail: hktsao@cc.ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Department of Physics, National Central University, Jhongli 320, Taiwan (China)

2016-11-01

Highlights: • Contact angle hysteresis(CAH) on four graphitic surfacesisinvestigated. • The hysteresis loopof water drops on the polished graphite sheetshowsparticularly small receding contact angle. • The significant CAH observed on CVD graphene and highly oriented pyrolytic graphite is attributed mainly to adhesion hysteresis. • An oil-infused surface of a graphite sheet is produced by imbibition of hexadecane into its porous structure. • The hysteresis-free property for water drops on such a surface is examined and quantitatively explained. - Abstract: Contact angle hysteresis (CAH) on graphitic surfaces, including chemical vapor deposition (CVD) graphene, reduced electrophoretic deposition (EPD) graphene, highly oriented pyrolytic graphite (HOPG), and polished graphite sheet, has been investigated. The hysteresis loops of water drops on the first three samples are similar but the receding contact angle is particularly small for the polished graphite sheet.The significant CAH observed on CVD graphene and HOPG associated with atom-scale roughness has to be attributed mainly to adhesion hysteresis (surface relaxation), instead of roughness or defects.The difference of the wetting behavior among those four graphitic samples has been further demonstrated by hexadecane drops. On the surface of HOPG or CVD graphene,the contact line expands continuously with time, indicating total wetting for which the contact angle does not exist and contact line pinning disappears. In contrast, on the surface of reduced EPD graphene, spontaneous spreading is halted by spikes on it and partial wetting with small contact angle (θ≈4°) is obtained. On the surface of polished graphite sheet, the superlipophilicity and porous structure are demonstrated by imbibition and capillary rise of hexadecane. Consequently, an oil-infused graphite surface can be fabricated and the ultralow CAH of water (∆θ≈2°) is achieved.

Theoretical approach to the magnetocaloric effect with hysteresis

International Nuclear Information System (INIS)

Basso, V.; Bertotti, G.; LoBue, M.; Sasso, C.P.

2005-01-01

In this paper a thermodynamic model with internal variables is presented and applied to ferromagnetic hysteresis. The out-of-equilibrium Gibbs free energy of a magnetic system is expressed as a function of the internal state of the Preisach model. Expressions for the system entropy and the entropy production are derived. By this approach it is possible to reproduce the characteristic features of the experimentally observed temperature changes (of the order of 10 -4 K around room temperature) induced by the magnetic field along the hysteresis loop performed in iron under adiabatic condition

"Shape function + memory mechanism"-based hysteresis modeling of magnetorheological fluid actuators

Science.gov (United States)

Qian, Li-Jun; Chen, Peng; Cai, Fei-Long; Bai, Xian-Xu

2018-03-01

A hysteresis model based on "shape function + memory mechanism" is presented and its feasibility is verified through modeling the hysteresis behavior of a magnetorheological (MR) damper. A hysteresis phenomenon in resistor-capacitor (RC) circuit is first presented and analyzed. In the hysteresis model, the "memory mechanism" originating from the charging and discharging processes of the RC circuit is constructed by adopting a virtual displacement variable and updating laws for the reference points. The "shape function" is achieved and generalized from analytical solutions of the simple semi-linear Duhem model. Using the approach, the memory mechanism reveals the essence of specific Duhem model and the general shape function provides a direct and clear means to fit the hysteresis loop. In the frame of the structure of a "Restructured phenomenological model", the original hysteresis operator, i.e., the Bouc-Wen operator, is replaced with the new hysteresis operator. The comparative work with the Bouc-Wen operator based model demonstrates superior performances of high computational efficiency and comparable accuracy of the new hysteresis operator-based model.

Polarization-dependent asymmetric hysteresis behavior in ZnCrO layers

International Nuclear Information System (INIS)

Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon; Fu, Dejun

2012-01-01

A ZnCrO layer grown on a Pt (111)/Al 2 O 3 (0001) substrate exhibits a lattice displacement induced ferroelectric behavior due to a modulation in the lattice translation symmetry. The top-to-bottom Pt/ZnCrO/Pt structure shows asymmetric hysteresis loops in positive and negative voltage bias regions. This is attributed to a change in the Schottky emission rate due to the nonlinear polarization of the ZnCrO barrier. The characteristics of the hysteresis loops depend on the film textures of ZnCrO, which vary with the oxygen partial pressure during the growth stage of the ZnCrO layers. The results suggest that ZnCrO has efficacy characteristics for applications in the non-volatile resistive-switching systems.

Magnetoresistance and Microstructure of Magnetite Nanocrystals Dispersed in Indium−Tin Oxide Thin Films

OpenAIRE

Okada, Koichi; Kohiki, Shigemi; Mitome, Masanori; Tanaka, Hidekazu; Arai, Masao; Mito, Masaki; Deguchi, Hiroyuki

2009-01-01

Epitaxial indium−tin oxide (ITO) thin films were fabricated on a yttria-stabilized zirconia (YSZ) substrate by pulsed-laser deposition using magnetite (Fe3O4) nanoparticle dispersed ITO powders as a target. Magnetoresistance of the film at a field of 1 T was 39% at 45 K, and it stayed at 3% above 225 K. The film demonstrated cooling hysteresis in the temperature dependence of direct-current magnetization. Transmission electron microscopy revealed that phase-separated Fe3O4 nanocrystals with w...

Hysteresis in Magnetocaloric Materials

DEFF Research Database (Denmark)

von Moos, Lars

, obtained at the initial low and final high field. However, in first order materials thermal entropy hysteresis loops are obtained through characterization, corresponding to measurements done in an increasing and a decreasing temperature mode. Indirectly determining the MCE through the use of the Maxwell...... order materials, taking the magnetic and thermal history dependence of material properties into account, as well as the heat production due to hysteretic losses. MnFe(P,As) and Gd5Si2Ge2 compounds are modelled and it is found that the Preisach approach is suitable to reproduce material behavior in both......In this thesis the effects of hysteresis on magnetocaloric material properties and their performance in magnetic refrigeration devices are investigated. This is done through an experimental and model study of first order magnetocaloric materials MnFe(P,As) and Gd5Si2Ge2. The experimental...

A combined Preisach–Hyperbolic Tangent model for magnetic hysteresis of Terfenol-D

Energy Technology Data Exchange (ETDEWEB)

Talebian, Soheil [Department of Mechanical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Hojjat, Yousef, E-mail: yhojjat@modares.ac.ir [Department of Mechanical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Ghodsi, Mojtaba [Department of Mechanical and Industrial Engineering, Sultan Qaboos University, Muscat (Oman); Karafi, Mohammad Reza [Department of Mechanical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mirzamohammadi, Shahed [Department of Mechanical Engineering, Shahid Rajaee University, Tehran (Iran, Islamic Republic of)

2015-12-15

This study presents a new model using the combination of Preisach and Hyperbolic Tangent models, to predict the magnetic hysteresis of Terfenol-D at different frequencies. Initially, a proper experimental setup was fabricated and used to obtain different magnetic hysteresis curves of Terfenol-D; such as major, minor and reversal loops. Then, it was shown that the Hyperbolic Tangent model is precisely capable of modeling the magnetic hysteresis of the Terfenol-D for both rate-independent and rate-dependent cases. Empirical equations were proposed with respect to magnetic field frequency which can calculate the non-dimensional coefficients needed by the model. These empirical equations were validated at new frequencies of 100 Hz and 300 Hz. Finally, the new model was developed through the combination of Preisach and Hyperbolic Tangent models. In the combined model, analytical relations of the Hyperbolic Tangent model for the first order reversal loops determined the weighting function of the Preisach model. This model reduces the required experiments and errors due to numerical differentiations generally needed for characterization of the Preisach function. In addition, it can predict the rate-dependent hysteresis as well as rate-independent hysteresis. - Highlights: • Different hysteresis curves of Terfenol-D are experimentally obtained at 0–200 Hz. • A new model is presented using combination of Preisach and Hyperbolic Tangent models. • The model predicts both rate-independent and rate-dependent hystereses of Terfenol-D. • The analytical model reduces the numerical errors and number of required experiments.

Modeling of quasistatic magnetic hysteresis with feed-forward neural networks

International Nuclear Information System (INIS)

Makaveev, Dimitre; Dupre, Luc; De Wulf, Marc; Melkebeek, Jan

2001-01-01

A modeling technique for rate-independent (quasistatic) scalar magnetic hysteresis is presented, using neural networks. Based on the theory of dynamic systems and the wiping-out and congruency properties of the classical scalar Preisach hysteresis model, the choice of a feed-forward neural network model is motivated. The neural network input parameters at each time step are the corresponding magnetic field strength and memory state, thereby assuring accurate prediction of the change of magnetic induction. For rate-independent hysteresis, the current memory state can be determined by the last extreme magnetic field strength and induction values, kept in memory. The choice of a network training set is motivated and the performance of the network is illustrated for a test set not used during training. Very accurate prediction of both major and minor hysteresis loops is observed, proving that the neural network technique is suitable for hysteresis modeling. [copyright] 2001 American Institute of Physics

Piezoelectric stack actuator parameter extraction with hysteresis compensation

DEFF Research Database (Denmark)

Zsurzsan, Tiberiu-Gabriel; Mangeot, Charles; Andersen, Michael A. E.

2014-01-01

The Piezoelectric Actuator Drive (PAD) is a type of rotary motor that transforms the linear motion of piezoelectric stack actuators into a precise rotational motion. The very high stiffness of the actuators employed make this type of motor suited for open-loop control, but the inherent hysteresis...

Polarization-dependent asymmetric hysteresis behavior in ZnCrO layers

Energy Technology Data Exchange (ETDEWEB)

Lee, Youngmin; Kim, Deukyoung; Lee, Sejoon [Dongguk University, Seoul (Korea, Republic of); Fu, Dejun [Wuhan University, Wuhan (China)

2012-06-15

A ZnCrO layer grown on a Pt (111)/Al{sub 2}O{sub 3} (0001) substrate exhibits a lattice displacement induced ferroelectric behavior due to a modulation in the lattice translation symmetry. The top-to-bottom Pt/ZnCrO/Pt structure shows asymmetric hysteresis loops in positive and negative voltage bias regions. This is attributed to a change in the Schottky emission rate due to the nonlinear polarization of the ZnCrO barrier. The characteristics of the hysteresis loops depend on the film textures of ZnCrO, which vary with the oxygen partial pressure during the growth stage of the ZnCrO layers. The results suggest that ZnCrO has efficacy characteristics for applications in the non-volatile resistive-switching systems.

Colossal magnetoresistance

International Nuclear Information System (INIS)

Fontcuberta, J.

1999-01-01

In 1986 Alex Mueller and Georg Bednorz of IBM Zurich discovered high-temperature superconductivity in copper-based oxides. This finding, which was rewarded with the Nobel Prize for Physics in the following year, triggered intense research into the properties of the transition metal oxides. Since then scientists have questioned the very nature of the metallic state in these materials. A few years after the initial discovery, in 1993, more excitement greeted reports that certain manganese oxides showed a huge change in electrical resistivity when a magnetic field was applied. This effect is generally known as magnetoresistance, but the resistivity change observed in these oxides was so large that it could not be compared with any other forms of magnetoresistance. The effect observed in these materials the manganese perovskites was therefore dubbed ''colossal'' magnetoresistance to distinguish it from the giant magnetoresistance observed in magnetic multilayers. In this article the author explains why magnetoresistance is an expanding field of physics research. (UK)

Giant magnetoresistance and extraordinary magnetoresistance in inhomogeneous semiconducting DyNiBi

OpenAIRE

Casper, Frederick; Felser, Claudia

2007-01-01

The semiconducting half-Heulser compound DyNiBi shows a negative giant magnetoresistance (GMR) below 200 K. Except for a weak deviation, this magnetoresistance scales roughly with the square of the magnetization in the paramagnetic state, and is related to the metal-insulator transition. At low temperature, a positive magnetoresistance is found, which can be suppressed by high fields. The magnitude of the positive magnetoresistance changes slightly with the amount of impurity phase.

Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model

Energy Technology Data Exchange (ETDEWEB)

Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

2012-03-15

The nature (time variation) of response magnetization m(wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h(wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m(wt) and h(wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical ( Bullet ), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results. - Highlights: Black-Right-Pointing-Pointer Kinetic spin-1 Blume-Capel model is studied using the effective-field theory. Black-Right-Pointing-Pointer We investigated the dynamic magnetic hysteresis behavior. Black-Right-Pointing-Pointer Dynamic magnetization, hysteresis loop area and correlation are investigated. Black-Right-Pointing-Pointer System exhibits tricritical, zero-temperature, triple and multicritical points. Black-Right-Pointing-Pointer We present the dynamic phase diagrams and compare the results of the EFT

Modeling and inverse feedforward control for conducting polymer actuators with hysteresis

International Nuclear Information System (INIS)

Wang, Xiangjiang; Alici, Gursel; Tan, Xiaobo

2014-01-01

Conducting polymer actuators are biocompatible with a small footprint, and operate in air or liquid media under low actuation voltages. This makes them excellent actuators for macro- and micro-manipulation devices, however, their positioning ability or accuracy is adversely affected by their hysteresis non-linearity under open-loop control strategies. In this paper, we establish a hysteresis model for conducting polymer actuators, based on a rate-independent hysteresis model known as the Duhem model. The hysteresis model is experimentally identified and integrated with the linear dynamics of the actuator. This combined model is inverted to control the displacement of the tri-layer actuators considered in this study, without using any external feedback. The inversion requires an inverse hysteresis model which was experimentally identified using an inverse neural network model. Experimental results show that the position tracking errors are reduced by more than 50% when the hysteresis inverse model is incorporated into an inversion-based feedforward controller, indicating the potential of the proposed method in enabling wider use of such smart actuators. (paper)

Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

International Nuclear Information System (INIS)

Kocakaplan, Yusuf; Keskin, Mustafa

2014-01-01

The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement

Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system

Energy Technology Data Exchange (ETDEWEB)

Kocakaplan, Yusuf [Graduate School of Natural and Applied Sciences, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

2014-09-07

The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

Pinched hysteresis behavior in a PID-controlled resistor

Directory of Open Access Journals (Sweden)

M.A. Carrasco-Aguilar

2018-06-01

Full Text Available A current-controlled grounded resistor that exhibits a frequency-dependent pinched hysteresis loop is described. A mathematical model describing this behavior is derived and validated numerically, which has the form of a Proportional Integral-Derivative (PID controller. The proposed topology is build by using AD844 commercially available active device configured as second-generation current conveyor and experimental tests are compared with numerical simulations, showing a good agreement among them. Moreover, the proposed PID-controlled resistor can be reconfigured in order to be used in future applications such as programmable analog circuits. Keyword: Pinched hysteresis, Current conveyors, Nonlinear resistor, Proportional-Integral-Derivative Controller

Interpreting diel hysteresis between soil respiration and temperature

Science.gov (United States)

C. Phillips; N. Nickerson; D. Risk; B.J. Bond

2011-01-01

Increasing use of automated soil respiration chambers in recent years has demonstrated complex diel relationships between soil respiration and temperature that are not apparent from less frequent measurements. Soil surface flux is often lagged from soil temperature by several hours, which results in semielliptical hysteresis loops when surface flux is plotted as a...

A RSM-based predictive model to characterize heat treating parameters of D2 steel using combined Barkhausen noise and hysteresis loop methods

International Nuclear Information System (INIS)

Kahrobaee, Saeed; Hejazi, Taha-Hossein

2017-01-01

Highlights: • A statistical relationship between NDE inputs and heat treating outputs was provided. • Predicting austenitizing/tempering temperatures at unknown heat treating conditions. • An optimization model that achieves minimum error in prediction was developed. • Applying two simultaneous magnetic NDE methods led to better measuring reliability. - Abstract: Austenitizing and tempering temperatures are the effective characteristics in heat treating process of AISI D2 tool steel. Therefore, controlling them enables the heat treatment process to be designed more accurately which results in more balanced mechanical properties. The aim of this work is to develop a multiresponse predictive model that enables finding these characteristics based on nondestructive tests by a set of parameters of the magnetic Barkhausen noise technique and hysteresis loop method. To produce various microstructural changes, identical specimens from the AISI D2 steel sheet were austenitized in the range 1025–1130 °C, for 30 min, oil-quenched and finally tempered at various temperatures between 200 °C and 650 °C. A set of nondestructive data have been gathered based on general factorial design of experiments and used for training and testing the multiple response surface model. Finally, an optimization model has been proposed to achieve minimal error prediction. Results revealed that applying Barkhausen and hysteresis loop methods, simultaneously, coupling to the multiresponse model, has a potential to be used as a reliable and accurate nondestructive tool for predicting austenitizing and tempering temperatures (which, in turn, led to characterizing the microstructural changes) of the parts with unknown heat treating conditions.

A RSM-based predictive model to characterize heat treating parameters of D2 steel using combined Barkhausen noise and hysteresis loop methods

Energy Technology Data Exchange (ETDEWEB)

Kahrobaee, Saeed, E-mail: kahrobaee@sadjad.ac.ir [Department of Mechanical and Materials Engineering, Sadjad University of Technology, P.O. Box 91881-48848, Mashhad (Iran, Islamic Republic of); Hejazi, Taha-Hossein [Department of Industrial Engineering and Management, Sadjad University of Technology, P.O. Box 91881-48848, Mashhad (Iran, Islamic Republic of)

2017-07-01

Highlights: • A statistical relationship between NDE inputs and heat treating outputs was provided. • Predicting austenitizing/tempering temperatures at unknown heat treating conditions. • An optimization model that achieves minimum error in prediction was developed. • Applying two simultaneous magnetic NDE methods led to better measuring reliability. - Abstract: Austenitizing and tempering temperatures are the effective characteristics in heat treating process of AISI D2 tool steel. Therefore, controlling them enables the heat treatment process to be designed more accurately which results in more balanced mechanical properties. The aim of this work is to develop a multiresponse predictive model that enables finding these characteristics based on nondestructive tests by a set of parameters of the magnetic Barkhausen noise technique and hysteresis loop method. To produce various microstructural changes, identical specimens from the AISI D2 steel sheet were austenitized in the range 1025–1130 °C, for 30 min, oil-quenched and finally tempered at various temperatures between 200 °C and 650 °C. A set of nondestructive data have been gathered based on general factorial design of experiments and used for training and testing the multiple response surface model. Finally, an optimization model has been proposed to achieve minimal error prediction. Results revealed that applying Barkhausen and hysteresis loop methods, simultaneously, coupling to the multiresponse model, has a potential to be used as a reliable and accurate nondestructive tool for predicting austenitizing and tempering temperatures (which, in turn, led to characterizing the microstructural changes) of the parts with unknown heat treating conditions.

Giant magnetoresistance and magnetostriction in Mn1.8Co0.2Sb

International Nuclear Information System (INIS)

Kushwaha, Pallavi; Lakhani, Archna; Rawat, R.

2007-01-01

We have studied the first order ferrimagnetic (FRI) to antiferromagnetic (AFM) transition in Mn l.8 Co 0.2 Sb by resistivity, magneto resistance and magnetostriction. With the application of magnetic field FRI to AFM transition temperature (T N ) decreases monotonically and hysteresis across the transition increases. Below T N FRI to AFM transition can be induced with the application of magnetic field which results in giant magnetoresistance and magnetostriction. The magnetostriction is found to be anomalous in this compound showing a small negative minimum close to critical field required for AFM to FRI transition. (author)

Disorder Identification in Hysteresis Data: Recognition Analysis of the Random-Bond-Random-Field Ising Model

International Nuclear Information System (INIS)

Ovchinnikov, O. S.; Jesse, S.; Kalinin, S. V.; Bintacchit, P.; Trolier-McKinstry, S.

2009-01-01

An approach for the direct identification of disorder type and strength in physical systems based on recognition analysis of hysteresis loop shape is developed. A large number of theoretical examples uniformly distributed in the parameter space of the system is generated and is decorrelated using principal component analysis (PCA). The PCA components are used to train a feed-forward neural network using the model parameters as targets. The trained network is used to analyze hysteresis loops for the investigated system. The approach is demonstrated using a 2D random-bond-random-field Ising model, and polarization switching in polycrystalline ferroelectric capacitors.

Hysteresis behaviour of thermoelastic alloys: some shape memory alloys models

International Nuclear Information System (INIS)

Lexcellent, C.; Torra, V.; Raniecki, B.

1993-01-01

The hysteretic behaviour of shape memory alloys (SMA) needs a more and more thin analysis because of its importance for technological applications. The comparison between different approaches allows to explicite the specifity of every model (macroscopic approach, micro-macro level, local description, phenomenological approach) and their points of convergence. On one hand, a thermodynamic treatment with a free energy expression as a mixing rule of each phase (parent or austenite phase and martensite) by adding a coupling term: the configurational energy, allowes modelling of material hysteresis loops. On the other hand, a phenomenological treatment based on a local investigation of two single crystals with a visualisation of microscopic parameters allows to perceive the phase transition mechanisms (nucleation, growth). All the obtained results show the importance of entropy production (or of the definition of the configurational energy term) for the correct description of hysteresis loops (subloops or external). (orig.)

Magnetoresistive logic and biochip

International Nuclear Information System (INIS)

Brueckl, Hubert; Brzeska, Monika; Brinkmann, Dirk; Schotter, J.Joerg; Reiss, Guenter; Schepper, Willi; Kamp, P.-B.; Becker, Anke

2004-01-01

While some magnetoresistive devices based on giant magnetoresistance or spin-dependent tunneling are already commercialized, a new branch of development is evolving towards magnetoresistive logic with magnetic tunnel junctions. Furthermore, the new magnetoelectronic effects show promising properties in magnetoresistive biochips, which are capable of detecting even single molecules (e.g. DNA) by functionalized magnetic markers. The unclear limits of this approach are discussed with two model systems

Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes

Science.gov (United States)

Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem

2014-02-01

The Gd5Ge2Si2 alloy and the off-stoichiometric Ni50Mn35In15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd5Ge2Si2 and Ni50Mn35In15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis.

Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes

International Nuclear Information System (INIS)

Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem

2014-01-01

The Gd 5 Ge 2 Si 2 alloy and the off-stoichiometric Ni 50 Mn 35 In 15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd 5 Ge 2 Si 2 and Ni 50 Mn 35 In 15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis

A GCMC simulation and experimental study of krypton adsorption/desorption hysteresis on a graphite surface.

Science.gov (United States)

Prasetyo, Luisa; Horikawa, Toshihide; Phadungbut, Poomiwat; Johnathan Tan, Shiliang; Do, D D; Nicholson, D

2016-09-15

Adsorption isotherms and isosteric heats of krypton on a highly graphitized carbon black, Carbopack F, have been studied with a combination of Monte Carlo simulation and high-resolution experiments at 77K and 87K. Our investigation sheds light on the microscopic origin of the experimentally observed, horizontal hysteresis loop in the first layer, and the vertical hysteresis-loop in the second layer, and is found to be in agreement with our recent Monte Carlo simulation study (Diao et al., 2015). From detailed analysis of the adsorption isotherm, the latter is attributed to the compression of an imperfect solid-like state in the first layer, to form a hexagonally packed, solid-like state, immediately following the first order condensation of the second layer. To ensure that capillary condensation in the confined spaces between microcrystallites of Carbopack F does not interfere with these hysteresis loops, we carried out simulations of krypton adsorption in the confined space of a wedge-shaped pore that mimics the interstices between particles. These simulations show that, up to the third layer, any such interference is negligible. Copyright © 2016 Elsevier Inc. All rights reserved.

Current perpendicular to plane giant magnetoresistance and tunneling magnetoresistance treated with unified model

NARCIS (Netherlands)

Jonkers, PAE

2002-01-01

The conceptual similarity between current perpendicular to plane giant magnetoresistance (CPP-GMR) and tunneling magnetoresistance (TMR) is exploited by utilizing a unified single-particle model accounting for both types of magnetoresistance. By defining structures composed of ferromagnetic,

Quantum oscillations and ferromagnetic hysteresis observed in iron filled multiwall carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Barzola-Quiquia, Jose; Klingner, Niko; Molle, Axel [Division of Superconductivity and Magnetism, University of Leipzig, D-04103 Leipzig (Germany); Leonhardt, Albrecht [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany)

2011-07-01

Carbon-based materials as multiwall carbon nanotubes (MWCNT) are attractive for spintronics because spin is only weakly coupled to the lattice, leading to large spin-flip scattering length and long spin relaxation times. In this contribution we have investigated the electrical transport properties of iron filled MWCNT (outer diameter 150 nm, inner diameter 25 nm and length 2000 nm) as a function of temperature and magnetic field. We observed quantum interference effects, i.e. universal conductance fluctuations, and weak localization effects. The in-plane magnetoresistance shows typical butterfly structure revealing the ferromagnetic properties of the Fe-filled MWCNT. The ferromagnetic hysteresis was observed up to 40K.

Capillary condensation in porous materials. Hysteresis and interaction mechanism without pore blocking/percolation process.

Science.gov (United States)

Grosman, Annie; Ortega, Camille

2008-04-15

We have performed measurements of boundary hysteresis loops, reversal curves, and subloops in p+-type porous silicon, a porous material composed of straight non-interconnected pores. These data show that a strong interaction mechanism exists between the pores. The pores of porous silicon are non-independent, whereas they are not interconnected. This hysteretic behavior is very similar to that observed in porous glass, which consists of cavities connected to each other by constrictions. This questions the so-called pore blocking/percolation model developed to explain the behavior of fluid in porous glass. More generally, if we disregard the shape of the boundary hysteresis loops which depends on the porous material (H1 for MCM-41 and SBA-15, H2 for porous glass and p+-type porous silicon), the hysteretic features inside the main loop are qualitatively the same for all these porous systems. This shows that none of these systems are composed of independent pores. A coupling between the pores is always present whether they are interconnected or not and whatever the shape of the main loop is.

Interplay between magnetocrystalline anisotropy and exchange bias in epitaxial CoO/Co films

International Nuclear Information System (INIS)

Liu, Hao-Liang; Zeng, Yu-Jia; Van Haesendonck, Chris; Brems, Steven; Temst, Kristiaan; Vantomme, André

2016-01-01

The interplay between magnetocrystalline anisotropy and exchange bias is investigated in CoO/Co bilayer films, which are grown epitaxially on MgO (0 0 1), by magnetization reversal measurements based on the anisotropic magnetoresistance (AMR) effect. While an asymmetric magnetization reversal survives after training for cooling field (CF) along the hard axis, the magnetization reversal becomes symmetric and is dominated in both branches of the hysteresis loop by domain wall motion before and after training for CF along the easy axis. When performing an in-plane hysteresis loop perpendicular to the CF, the hysteresis loop along the easy axis becomes asymmetric: magnetization rotation dominates in the ascending branch, while there is a larger contribution of domain wall motion in the descending branch. Furthermore, the azimuthal angular dependence of the AMR shows two minima after performing a perpendicular hysteresis loop, instead of only one minimum after training. Relying on the extended Fulcomer and Charap model, these effects can be related to an increased deviation of the average uncompensated antiferromagnetic magnetization from the CF direction. This model provides a consistent interpretation of training and asymmetry of the magnetization reversal for epitaxial films with pronounced magnetocrystalline anisotropy as well as for the previously investigated polycrystalline films. (paper)

Comparison of angular dependence of magnetic Barkhausen noise of hysteresis and initial magnetization curve in API5L steel

Science.gov (United States)

Chávez-Gonzalez, A. F.; Martínez-Ortiz, P.; Pérez-Benítez, J. A.; Espina-Hernández, J. H.; Caleyo, F.

2018-01-01

This work analyzes the differences between the magnetic Barkhausen noise corresponding to the initial magnetization curve and Barkhausen noise corresponding to one branch of the hysteresis loop in API-5L steel. The outcomes show that the Barkhausen noise signal corresponding to the initial magnetization curve and that corresponding to the hysteresis are significantly different. This difference is due to the presence of different processes of the domain wall dynamics in both phenomena. To study the processes present in magnetization dynamics for an applied field of H > 0, research into the angular dependence of a Barkhausen signal using applied field bands has revealed that a Barkhausen signal corresponding to the initial magnetization curve is more suitable than a Barkhausen signal corresponding to the hysteresis loop.

Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

International Nuclear Information System (INIS)

Deviren, Bayram; Keskin, Mustafa

2012-01-01

The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

Energy Technology Data Exchange (ETDEWEB)

Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

2012-02-20

The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

Hysteresis losses of magnetic nanoparticle powders in the single domain size range

International Nuclear Information System (INIS)

Dutz, S.; Hergt, R.; Muerbe, J.; Mueller, R.; Zeisberger, M.; Andrae, W.; Toepfer, J.; Bellemann, M.E.

2007-01-01

Magnetic iron oxide nanoparticle powders were investigated in order to optimise the specific hysteresis losses for biomedical heating applications. Different samples with a mean particle size in the transition range from superparamagnetic to ferromagnetic behaviour (i.e. 10-100 nm) were prepared by two different chemical precipitation routes. Additionally, the influence of milling and annealing on hysteresis losses of the nanoparticles was investigated. Structural investigations of the samples were carried out by X-ray diffraction, measurement of specific surface area, and scanning and transmission electron microscopy. The dependence of hysteresis losses of minor loops on the field amplitude was determined using vibrating sample magnetometry and caloric measurements. For small field amplitudes, a power law was found which changes into saturation at amplitudes well above the coercive field. Maximum hysteresis losses of 6.6 J/kg per cycle were observed for milled powder. For field amplitudes below about 10 kA/m, which are especially interesting for medical and technical applications, hysteresis losses of all investigated powders were at least by one order of magnitude lower than reported for magnetosomes of comparable size

Hysteresis loops and the demagnetization process at 4.2 K for melt-spun Nd sub 1 sub 3 Fe sub 7 sub 7 B sub 1 sub 0

CERN Document Server

Jin Han Min; Park, W S; Park, M J; Wang Xue Feng

1998-01-01

Hysteresis loops of melt-spun Nd sub 1 sub 3 Fe sub 7 sub 7 B sub 1 sub 0 cooled down at the remanent state were measured at 4.2 K. The loop for fields of H sub m sub a sub x =6.4 MA m sup - sup 1 is characterized by low- and high-field steps. The loop for fields of H sub m sub a sub x =4.0 MA m sup - sup 1 is very thin with only a low-field step and is shifted profoundly along the H-axes. The loops and the spin distribution during the demagnetization process were analysed by micromagnetic finite-element calculations. Quantitatively, the calculations reproduce the experimental loops fairly well. The spin distribution is fairly nonuniform, and a domain-wall-like distribution appears not only at some grain boundaries but also within some grains at the high-field step. The demagnetization proceeds by nonuniform reversion as a whole, and neither the model of single-domain reversion nor the model of domain-wall pinning in the grain boundary model describes the process appropriately. (author)

A self-adaptive genetic algorithm to estimate JA model parameters considering minor loops

Energy Technology Data Exchange (ETDEWEB)

Lu, Hai-liang; Wen, Xi-shan; Lan, Lei; An, Yun-zhu; Li, Xiao-ping

2015-01-15

A self-adaptive genetic algorithm for estimating Jiles–Atherton (JA) magnetic hysteresis model parameters is presented. The fitness function is established based on the distances between equidistant key points of normalized hysteresis loops. Linearity function and logarithm function are both adopted to code the five parameters of JA model. Roulette wheel selection is used and the selection pressure is adjusted adaptively by deducting a proportional which depends on current generation common value. The Crossover operator is established by combining arithmetic crossover and multipoint crossover. Nonuniform mutation is improved by adjusting the mutation ratio adaptively. The algorithm is used to estimate the parameters of one kind of silicon-steel sheet’s hysteresis loops, and the results are in good agreement with published data. - Highlights: • We present a method to find JA parameters for both major and minor loops. • Fitness function is based on distances between key points of normalized loops. • The selection pressure is adjusted adaptively based on generations.

A self-adaptive genetic algorithm to estimate JA model parameters considering minor loops

International Nuclear Information System (INIS)

Lu, Hai-liang; Wen, Xi-shan; Lan, Lei; An, Yun-zhu; Li, Xiao-ping

2015-01-01

A self-adaptive genetic algorithm for estimating Jiles–Atherton (JA) magnetic hysteresis model parameters is presented. The fitness function is established based on the distances between equidistant key points of normalized hysteresis loops. Linearity function and logarithm function are both adopted to code the five parameters of JA model. Roulette wheel selection is used and the selection pressure is adjusted adaptively by deducting a proportional which depends on current generation common value. The Crossover operator is established by combining arithmetic crossover and multipoint crossover. Nonuniform mutation is improved by adjusting the mutation ratio adaptively. The algorithm is used to estimate the parameters of one kind of silicon-steel sheet’s hysteresis loops, and the results are in good agreement with published data. - Highlights: • We present a method to find JA parameters for both major and minor loops. • Fitness function is based on distances between key points of normalized loops. • The selection pressure is adjusted adaptively based on generations

Hysteresis Compensation and Sliding Mode Control with Perturbation Estimation for Piezoelectric Actuators

Directory of Open Access Journals (Sweden)

Bingxiao Ding

2018-05-01

Full Text Available Based on the background of atomic force microscope (AFM driven by piezoelectric actuators (PEAs, this paper proposes a sliding mode control coupled with an inverse Bouc–Wen (BW hysteresis compensator to improve the positioning performance of PEAs. The intrinsic hysteresis and creep characteristics degrade the performance of the PEA and cause accuracy loss. Although creep effect can be eliminated by the closed-loop control approach, hysteresis effects need to be compensated and alleviated by hysteresis compensators. For the purpose of dealing with the estimation errors, unmodeled vibration, and disturbances, a sliding mode control with perturbation estimation (SMCPE method is adopted to enhance the performance and robustness of the system. In order to validate the feasibility and performance of the proposed method, experimental studies are carried out, and the results show that the proposed controller performs better than a proportional-integral-derivative (PID controller at 1 and 2 Hz, reducing error to 1.2% and 1.4%, respectively.

High-speed tracking control of piezoelectric actuators using an ellipse-based hysteresis model.

Science.gov (United States)

Gu, Guoying; Zhu, Limin

2010-08-01

In this paper, an ellipse-based mathematic model is developed to characterize the rate-dependent hysteresis in piezoelectric actuators. Based on the proposed model, an expanded input space is constructed to describe the multivalued hysteresis function H[u](t) by a multiple input single output (MISO) mapping Gamma:R(2)-->R. Subsequently, the inverse MISO mapping Gamma(-1)(H[u](t),H[u](t);u(t)) is proposed for real-time hysteresis compensation. In controller design, a hybrid control strategy combining a model-based feedforward controller and a proportional integral differential (PID) feedback loop is used for high-accuracy and high-speed tracking control of piezoelectric actuators. The real-time feedforward controller is developed to cancel the rate-dependent hysteresis based on the inverse hysteresis model, while the PID controller is used to compensate for the creep, modeling errors, and parameter uncertainties. Finally, experiments with and without hysteresis compensation are conducted and the experimental results are compared. The experimental results show that the hysteresis compensation in the feedforward path can reduce the hysteresis-caused error by up to 88% and the tracking performance of the hybrid controller is greatly improved in high-speed tracking control applications, e.g., the root-mean-square tracking error is reduced to only 0.34% of the displacement range under the input frequency of 100 Hz.

Low Field Magnetic and Thermal Hysteresis in Antiferromagnetic Dysprosium

Directory of Open Access Journals (Sweden)

Iuliia Liubimova

2017-06-01

Full Text Available Magnetic and thermal hysteresis (difference in magnetic properties on cooling and heating have been studied in polycrystalline Dy (dysprosium between 80 and 250 K using measurements of the reversible Villari effect and alternating current (AC susceptibility. We argue that measurement of the reversible Villari effect in the antiferromagnetic phase is a more sensitive method to detect magnetic hysteresis than the registration of conventional B(H loops. We found that the Villari point, recently reported in the antiferromagnetic phase of Dy at 166 K, controls the essential features of magnetic hysteresis and AC susceptibility on heating from the ferromagnetic state: (i thermal hysteresis in AC susceptibility and in the reversible Villari effect disappears abruptly at the temperature of the Villari point; (ii the imaginary part of AC susceptibility is strongly frequency dependent, but only up to the temperature of the Villari point; (iii the imaginary part of the susceptibility drops sharply also at the Villari point. We attribute these effects observed at the Villari point to the disappearance of the residual ferromagnetic phase. The strong influence of the Villari point on several magnetic properties allows this temperature to be ranked almost as important as the Curie and Néel temperatures in Dy and likely also for other rare earth elements and their alloys.

Detailed modeling of local anisotropy and transverse Ku interplay regarding hysteresis loop in FeCuNbSiB nanocrystalline ribbons

Science.gov (United States)

Geoffroy, Olivier; Boust, Nicolas; Chazal, Hervé; Flury, Sébastien; Roudet, James

2018-04-01

This article focuses on the modeling of the hysteresis loop featured by Fe-Cu-Nb-Si-B nanocrystalline alloys with transverse induced anisotropy. The magnetization reversal process of a magnetic correlated volume (CV), characterized by the induced anisotropy Ku, and a deviation of the local easy magnetization direction featuring the effect of a local incoherent anisotropy Ki, is analyzed, taking account of magnetostatic interactions. Solving the equations shows that considering a unique typical kind of CV does not enable accounting for both the domain pattern and the coercivity. Actually, the classical majority CVs obeying the random anisotropy model explains well the domain pattern but considering another kind of CVs, minority, mingled with classical ones, featuring a magnitude of Ki comparable to Ku, is necessary to account for coercivity. The model has been successfully compared with experimental data.

Characterization and modeling of magnetic domain wall dynamics using reconstituted hysteresis loops from Barkhausen noise

Energy Technology Data Exchange (ETDEWEB)

Ducharne, B., E-mail: Benjamin.ducharne@insa-lyon.fr; Le, M.Q.; Sebald, G.; Cottinet, P.J.; Guyomar, D.; Hebrard, Y.

2017-06-15

Highlights: • Barkhausen noise energy versus excitation field hysteresis cycles MBN{sub energy}(H). • Difference in the dynamics of the induction field B and of the MBN{sub energy}. • Dynamic behavior of MBN{sub energy}(H) cycles is first-order. • Dynamic behavior of B(H) cycles is non-entire order. - Abstract: By means of a post-processing technique, we succeeded in plotting magnetic Barkhausen noise energy hysteresis cycles MBN{sub energy}(H). These cycles were compared to the usual hysteresis cycles, displaying the evolution of the magnetic induction field B versus the magnetic excitation H. The divergence between these comparisons as the excitation frequency was increased gave rise to the conclusion that there was a difference in the dynamics of the induction field and of the MBN{sub energy} related to the domain wall movements. Indeed, for the MBN{sub energy} hysteresis cycle, merely the domain wall movements were involved. On the other hand, for the usual B(H) cycle, two dynamic contributions were observed: domain wall movements and diffusion of the magnetic field excitation. From a simulation point of view, it was demonstrated that over a large frequency bandwidth a correct dynamic behavior of the domain wall movement MBN{sub energy}(H) cycle could be taken into account using first-order derivation whereas fractional orders were required for the B(H) cycles. The present article also gives a detailed description of how to use the developed process to obtain the MBN{sub energy}(H) hysteresis cycle as well as its evolution as the frequency increases. Moreover, this article provides an interesting explanation of the separation of magnetic loss contributions through a magnetic sample: a wall movement contribution varying according to first-order dynamics and a diffusion contribution which in a lump model can be taken into account using fractional order dynamics.

Transverse thermal magnetoresistance of potassium

International Nuclear Information System (INIS)

Newrock, R.S.; Maxfield, B.W.

1976-01-01

Results are presented of extensive thermal magnetoresistance measurements on single-crystal and polycrystalline specimens of potassium having residual resistance ratios (RRR) ranging from 1100 to 5300. Measurements were made between 2 and 9 0 K for magnetic fields up to 1.8 T. The observed thermal magnetoresistance cannot be understood on the basis of either semiclassical theories or from the electrical magnetoresistance and the Wiedemann-Franz law. A number of relationships are observed between the thermal and electrical magnetoresistances, many of which are not immediately obvious when comparing direct experimental observations. The thermal magnetoresistance W(T,H) is given reasonably well by W(T,H)T = W(T,0)T + AH + BH 2 , where both A and B are temperature-dependent coefficients. Results show that A = A 0 + A 1 T 3 , while B(T) cannot be expressed as any simple power law. A 0 is dependent on the RRR, while A 1 is independent of the RRR. Two relationships are found between corresponding coefficients in the electrical and thermal magnetoresistance: (i) the Wiedmann--Franz law relates A 0 to the Kohler slope of the electrical magnetoresistance and (ii) the temperature-dependent portions of the electrical and thermal Kohler slopes are both proportional to the electron--phonon scattering contribution to the corresponding zero-field resistance. The latter provides evidence that inelastic scattering is very important in determining the temperature-dependent linear magnetoresistances. Part, but by no means all, of the quadratic thermal resistance is accounted for by lattice thermal conduction. It is concluded that at least a portion of the anomalous electrical and thermal magnetoresistances is due to intrinsic causes and not inhomogeneities or other macroscopic defects

An Experimental Study on Hysteresis Characteristics of a Pneumatic Braking System for a Multi-Axle Heavy Vehicle in Emergency Braking Situations

Directory of Open Access Journals (Sweden)

Zhe Wang

2017-08-01

Full Text Available This study aims to investigate the hysteresis characteristics of a pneumatic braking system for multi-axle heavy vehicles (MHVs. Hysteresis affects emergency braking performance severely. The fact that MHVs have a large size and complex structure leads to more nonlinear coupling property of the pneumatic braking system compared to normal two-axle vehicles. Thus, theoretical analysis and simulation are not enough when studying hysteresis. In this article, the hysteresis of a pneumatic brake system for an eight-axle vehicle in an emergency braking situation is studied based on a novel test bench. A servo drive device is applied to simulate the driver’s braking intensions normally expressed by opening or moving speed of the brake pedal. With a reasonable arrangement of sensors and the NI LabVIEW platform, both the delay time of eight loops and the response time of each subassembly in a single loop are detected in real time. The outcomes of the experiment show that the delay time of each loop gets longer with the increase of pedal opening, and a quadratic relationship exists between them. Based on this, the pressure transient in the system is fitted to a first-order plus time delay model. Besides, the response time of treadle valve and controlling pipeline accounts for more than 80% of the loop’s total delay time, indicating that these two subassemblies are the main contributors to the hysteresis effect.

Two component butterfly hysteresis in RuSr2EuCeCu2O1 ruthenocuprate

International Nuclear Information System (INIS)

Zivkovic, I.; Drobac, D.; Prester, M.

2006-01-01

We report detailed studies of the ac susceptibility butterfly hysteresis on the RuSr 2 EuCeCu 2 O 1 (Ru1222) ruthenocuprate compound. Two separate contributions to these hysteresis have been identified and studied. One contribution is ferromagnetic-like and is characterized by the coercive field maximum. Another contribution, represented by the so called inverted maximum, is related to the unusual inverted loops, unique feature of Ru1222 butterfly hysteresis. The different nature of the two identified magnetic contributions is proved by the different temperature dependences involved. By lowering the temperature the inverted peak gradually disappears while the coercive field slowly raises. If the maximum dc field for the hysteresis is increased, the size of the inverted part of the butterfly hysteresis monotonously grows while the position of the peak saturates. In reaching saturation exponential field dependence has been demonstrated to take place. At T = 78 K the saturation field is 42 Oe

The Hysteresis Performance and Restoring Force Model for Corroded Reinforced Concrete Frame Columns

Directory of Open Access Journals (Sweden)

Guifeng Zhao

2016-01-01

Full Text Available A numerical simulation of the hysteresis performance of corroded reinforced concrete (RC frame columns was conducted. Moreover, the results obtained were compared with experimental data. On this basis, a degenerated three-linearity (D-TRI restoring force model was established which could reflect the hysteresis performance of corroded RC frame columns through theoretical analysis and data fitting. Results indicated that the hysteretic bearing capacity of frame columns decreased significantly due to corrosion of the rebar. In view of the characteristics of the hysteresis curve, the plumpness of the hysteresis loop for frame columns decreased and shrinkage increased with increasing rebar corrosion. All these illustrated that the seismic energy dissipation performance of frame columns reduced but their brittleness increased. As for the features of the skeleton curve, the trends for corroded and noncorroded members were basically consistent and roughly corresponded to the features of a trilinear equivalent model. Thereby, the existing Clough hysteresis rule can be used to establish the restoring force model applicable to corroded RC frame columns based on that of the noncorroded RC members. The calculated skeleton curve and hysteresis curve of corroded RC frame columns using the D-TRI model are closer to the experimental results.

Position control of a single pneumatic artificial muscle with hysteresis compensation based on modified Prandtl-Ishlinskii model.

Science.gov (United States)

Zang, Xizhe; Liu, Yixiang; Heng, Shuai; Lin, Zhenkun; Zhao, Jie

2017-01-01

High-performance position control of pneumatic artificial muscles is limited by their inherent nonlinearity and hysteresis. This study aims to model the length/pressure hysteresis of a single pneumatic artificial muscle and to realize its accurate position tracking control with forward hysteresis compensation. The classical Prandtl-Ishlinskii model is widely used in hysteresis modelling and compensation. But it is only effective for symmetric hysteresis. Therefore, a modified Prandtl-Ishlinskii model is built to characterize the asymmetric length/pressure hysteresis of a single pneumatic artificial muscle, by replacing the classical play operators with two more flexible elementary operators to independently describe the ascending branch and descending branch of hysteresis loops. On the basis, a position tracking controller, which is composed of cascade forward hysteresis compensation and simple proportional pressure controller, is designed for the pneumatic artificial muscle. Experiment results show that the MPI model can reproduce the length/pressure hysteresis of the pneumatic artificial muscle, and the proposed controller for the pneumatic artificial muscle can track the reference position signals with high accuracy. By modelling the length/pressure hysteresis with the modified Prandtl-Ishlinskii model and using its inversion for compensation, precise position control of a single pneumatic artificial muscle is achieved.

Rashba-Edelstein Magnetoresistance in Metallic Heterostructures.

Science.gov (United States)

Nakayama, Hiroyasu; Kanno, Yusuke; An, Hongyu; Tashiro, Takaharu; Haku, Satoshi; Nomura, Akiyo; Ando, Kazuya

2016-09-09

We report the observation of magnetoresistance originating from Rashba spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein (RE) magnetoresistance. We show that the simultaneous action of the direct and inverse RE effects in a Bi/Ag/CoFeB trilayer couples current-induced spin accumulation to the electric resistance. The electric resistance changes with the magnetic-field angle, reminiscent of the spin Hall magnetoresistance, despite the fact that bulk SOC is not responsible for the magnetoresistance. We further found that, even when the magnetization is saturated, the resistance increases with increasing the magnetic-field strength, which is attributed to the Hanle magnetoresistance in this system.

Hysteresis Analysis and Positioning Control for a Magnetic Shape Memory Actuator

Science.gov (United States)

Lin, Jhih-Hong; Chiang, Mao-Hsiung

2015-01-01

Magnetic shape memory alloys (MSM alloys), a new kind of smart materials, have become a potential candidate in many engineering fields. MSMs have the advantage of bearing a huge strain, much larger than other materials. In addition, they also have fast response. These characteristics make MSM a good choice in micro engineering. However, MSMs display the obvious hysteresis phenomenon of nonlinear behavior. Thus the difficulty in using the MSM element as a positioning actuator is increased due to the hysteresis. In this paper, the hysteresis phenomenon of the MSM actuator is analyzed, and the closed-loop positioning control is also implemented experimentally. For that, a modified fuzzy sliding mode control (MFSMC) is proposed. The MFSMC and the PID control are used to design the controllers for realizing the positioning control. The experimental results are compared under different experimental conditions, such as different frequency, amplitude, and loading. The experimental results show that the precise positioning control of MFSMC can be achieved satisfactorily. PMID:25853405

Magnetic hysteresis and complex susceptibility as measures of ac losses in a multifilamentary NbTi superconductor

International Nuclear Information System (INIS)

Goldfarb, R.B.; Clark, A.F.

1985-01-01

Magnetization and ac susceptibility of a standard NbTi superconductor were measured as a function of longitudinal dc magnetic field. The ac-field-amplitude and frequency dependences of the complex susceptibility are examined. The magnetization is related to the susceptibility by means of a theoretical derivation based on the field dependence of the critical current density. Hysteresis losses, obtained directly from dc hysteresis loops and derived theoretically from ac susceptibility and critical current density, were in reasonable agreement

Identification techniques for phenomenological models of hysteresis based on the conjugate gradient method

International Nuclear Information System (INIS)

Andrei, Petru; Oniciuc, Liviu; Stancu, Alexandru; Stoleriu, Laurentiu

2007-01-01

An identification technique for the parameters of phenomenological models of hysteresis is presented. The basic idea of our technique is to set up a system of equations for the parameters of the model as a function of known quantities on the major or minor hysteresis loops (e.g. coercive force, susceptibilities at various points, remanence), or other magnetization curves. This system of equations can be either over or underspecified and is solved by using the conjugate gradient method. Numerical results related to the identification of parameters in the Energetic, Jiles-Atherton, and Preisach models are presented

Fast Magnetoresistive Random-Access Memory

Science.gov (United States)

Wu, Jiin-Chuan; Stadler, Henry L.; Katti, Romney R.

1991-01-01

Magnetoresistive binary digital memories of proposed new type expected to feature high speed, nonvolatility, ability to withstand ionizing radiation, high density, and low power. In memory cell, magnetoresistive effect exploited more efficiently by use of ferromagnetic material to store datum and adjacent magnetoresistive material to sense datum for readout. Because relative change in sensed resistance between "zero" and "one" states greater, shorter sampling and readout access times achievable.

Anomalous magnetoresistance in amorphous metals

International Nuclear Information System (INIS)

Kuz'menko, V.M.; Vladychkin, A.N.; Mel'nikov, V.I.; Sudovtsev, A.I.

1984-01-01

The magnetoresistance of amorphous Bi, Ca, V and Yb films is investigated in fields up to 4 T at low temperatures. For all metals the magnetoresistance is positive, sharply decreases with growth of temperature and depends anomalously on the magnetic field strength. For amorphous superconductors the results agree satisfactorily with the theory of anomalous magnetoresistance in which allowance is made for scattering of electrons by the superconducting fluctuations

Giant magnetoresistance through a single molecule.

Science.gov (United States)

Schmaus, Stefan; Bagrets, Alexei; Nahas, Yasmine; Yamada, Toyo K; Bork, Annika; Bowen, Martin; Beaurepaire, Eric; Evers, Ferdinand; Wulfhekel, Wulf

2011-03-01

Magnetoresistance is a change in the resistance of a material system caused by an applied magnetic field. Giant magnetoresistance occurs in structures containing ferromagnetic contacts separated by a metallic non-magnetic spacer, and is now the basis of read heads for hard drives and for new forms of random access memory. Using an insulator (for example, a molecular thin film) rather than a metal as the spacer gives rise to tunnelling magnetoresistance, which typically produces a larger change in resistance for a given magnetic field strength, but also yields higher resistances, which are a disadvantage for real device operation. Here, we demonstrate giant magnetoresistance across a single, non-magnetic hydrogen phthalocyanine molecule contacted by the ferromagnetic tip of a scanning tunnelling microscope. We measure the magnetoresistance to be 60% and the conductance to be 0.26G(0), where G(0) is the quantum of conductance. Theoretical analysis identifies spin-dependent hybridization of molecular and electrode orbitals as the cause of the large magnetoresistance.

Nature of dislocation hysteresis losses and nonlinear effect in lead at high vibration amplitudes

International Nuclear Information System (INIS)

Lomakin, V.V.; Pal-Val, L.N.; Platkov, V.Y.; Roshchupkin, A.M.

1982-01-01

The nature of the dislocation hysteresis was established and changes in this hysteresis were determined by investigating the dependence of the dislocation-induced absorption of ultrasound (coefficient α) on the amplitude of ultrasound epsilon-c 0 in single crystals of pure lead and of lead containing Tl and Sn impurities. The investigation was carried out in a wide range of epsilon-c 0 under superconducting transition conditions. In the superconducting (s) state both pure Pb and that doped with T1 exhibited a maximum in the dependence α(epsilon-c 0 ) at high values of epsilon-c 0 ; on transition to the normal (n) state this maximum changed to a plateau. This provided a direct proof of a change in the static nature of the dislocation hysteresis to the dynamic process because of an increase in the coefficient of the electron drag of dislocations. Estimates were obtained of the range of lengths of dislocation loops: 2.4 x 10 - 4 cm - 4 cm. In the case of lead containing Sn the dynamic hysteresis occurred both in the normal and superconducting states. In the range of amplitudes above that of the maximum and at the beginning of the plateau all single crystals exhibited a rise of α on increase of epsilon-c 0 in the superconducting and normal states; this rise was due to nonlinear effects observed in the case of strong bending of L/sub N/ loops. An analysis was made of the amplitude dependence of the losses associated with this effect. The results were in good agreement with the experimental data

Mutual influence between current-induced giant magnetoresistance and radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2DES.

Science.gov (United States)

Samaraweera, R L; Liu, H-C; Wang, Z; Reichl, C; Wegscheider, W; Mani, R G

2017-07-11

Radiation-induced magnetoresistance oscillations are examined in the GaAs/AlGaAs 2D system in the regime where an observed concurrent giant magnetoresistance is systematically varied with a supplementary dc-current, I dc . The I dc tuned giant magnetoresistance is subsequently separated from the photo-excited oscillatory resistance using a multi-conduction model in order to examine the interplay between the two effects. The results show that the invoked multiconduction model describes the observed giant magnetoresistance effect even in the presence of radiation-induced magnetoresistance oscillations, the magnetoresistance oscillations do not modify the giant magnetoresistance, and the magnetoresistance oscillatory extrema, i.e., maxima and minima, disappear rather asymmetrically with increasing I dc . The results suggest the interpretation that the I dc serves to suppress scattering between states near the Fermi level in a strong magnetic field limit.

A differential equation approach to minor loops in the Jiles-Atherton hysteresis model

International Nuclear Information System (INIS)

Carpenter, K.H.

1991-01-01

Jiles and Atherton, in a series of papers, present physically based differential equations for magnetization in ferromagnetic materials. however, if one directly solves their differential equations, the minor loops obtained can be negative slopes, which is a nonphysical behavior. Only one of their papers gives a method for obtaining minor loops, and the method does not use a differential equation, but requires a priori knowledge of the loop turning points in order to obtain a scale factor and offset which allow a portion of a major loop to serve as a portion of a minor one. In this paper, the reason for the failure of the differential equations to yield physical minor loops is explained, and a modified solution for minor loops is presented which retains the features of Jiles and Atherton's original minor loops, but only requires knowledge of the initial point on each portion of the loop to obtain the solution. This yields a general differential equation formulation for the Jiles-Atherton theory that can be used with circuit simulations having arbitrary excitations and initial conditions for ferromagnetic components

Nondestructive inspection of ductile cast iron by measurement of minor magnetic hysteresis loops

Czech Academy of Sciences Publication Activity Database

Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, Ivan

2010-01-01

Roč. 659, č. 9 (2010), 355-360 ISSN 0255-5476 R&D Projects: GA ČR GA101/09/1323; GA AV ČR 1QS100100508 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic NDE * magnetic adaptive testing * cast iron * magnetic hysteresis Subject RIV: BM - Solid Matter Physics ; Magnetism

Effect of the Hamiltonian parameters on the hysteresis properties of the kinetic mixed spin (1/2, 1) Ising ferrimagnetic model on a hexagonal lattice

Energy Technology Data Exchange (ETDEWEB)

Batı, Mehmet, E-mail: mehmet.bati@erdogan.edu.tr [Department of Physics, Recep Tayyip Erdoğan University, 53100 Rize (Turkey); Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

2017-05-15

The hysteresis properties of a kinetic mixed spin (1/2, 1) Ising ferrimagnetic system on a hexagonal lattice are studied by means of the dynamic mean field theory. In the present study, the effects of the nearest-neighbor interaction, temperature, frequency of oscillating magnetic field and the exchange anisotropy on the hysteresis properties of the kinetic system are discussed in detail. A number of interesting phenomena such as the shape of hysteresis loops with one, two, three and inverted-hysteresis/proteresis (butterfly shape hysteresis) have been obtained. Finally, the obtained results are compared with some experimental and theoretical results and a qualitatively good agreement is found.

A challenging hysteresis operator for the simulation of Goss-textured magnetic materials

Energy Technology Data Exchange (ETDEWEB)

Cardelli, Ermanno [Dipartimento di Ingegneria, Università di Perugia, Via G. Duranti, 67, 06125 Perugia (Italy); Centre for Electric and Magnetic Applied Research, Perugia (Italy); Faba, Antonio [Centre for Electric and Magnetic Applied Research, Perugia (Italy); Polo Didattico Scientifico di Terni, Strada Pentima Bassa n. 4, 05100 Terni (Italy); Laudani, Antonino [Università Roma tre, Via Ostiense, 159, 00154 Roma (Italy); Pompei, Michele [Dipartimento di Ingegneria, Università di Perugia, Via G. Duranti, 67, 06125 Perugia (Italy); Quondam Antonio, Simone, E-mail: simonequondam87@gmail.com [Dipartimento di Ingegneria, Università di Perugia, Via G. Duranti, 67, 06125 Perugia (Italy); Fulginei, Francesco Riganti; Salvini, Alessandro [Università Roma tre, Via Ostiense, 159, 00154 Roma (Italy)

2017-06-15

Highlights: • New 2-D hysteresis operator for the simulation of Goss-textured ferromagnets at macromagnetic scale-length. • The operator is derived from the classic Stoner–Wohlfarth but the in-plane magnetic anisotropy is cubic. • The single hysteron model is defined exploiting only one “moving” hysteresis operator. • Results are especially promising for FEM based calculations, where the magnetization state in each point must be recalculated at each time step. • Numerical accuracy is proved by comparison with measured data. - Abstract: A new hysteresis operator for the simulation of Goss-textured ferromagnets is here defined. The operator is derived from the classic Stoner–Wohlfarth model, where the anisotropy energy is assumed to be cubic instead of uniaxial, in order to reproduce the magnetic behavior of Goss textured ferromagnetic materials, such as grain-oriented Fe–Si alloys, Ni–Fe alloys, and Ni–Co alloys. A vector hysteresis model based on a single hysteresis operator is then implemented and used for the prediction of the rotational magnetizations that have been measured in a sample of grain-oriented electrical steel. This is especially promising for FEM based calculations, where the magnetization state in each point must be recalculated at each time step. Finally, the computed loops, as well as the magnetic losses, are compared to the measured data.

Negative hysteresis effect observed during calibration of the US Bureau of Mines borehole deformation gauge

International Nuclear Information System (INIS)

Ganow, H.C.

1985-08-01

The US Bureau of Mines borehole deformation gauge (BMG) was designed in the early 1960's to allow rock stress measurements by the overcoring method. Since that time it has become a de facto standard against which the performance of other borehole deformation gauges is often judged. However, during recent in situ stress studies in the Climax Stock at the Nevada Test Site a strange ''negative hysteresis'' in the order of 300 to 500 microstrains was observed in standard calibration data. Here, the relaxation curve lies below the indentation (compression) curves as if the system were to somehow respond with an energy release. Therefore, a precision micro-indentation apparatus has been designed and used to perform a series of tests allowing a better understanding of the BMG button to cantilever interaction. Results indicate that the hysteresis effect is caused by differential motion between the button base and the cantilever resulting from the geometric motion inherent in the cantilever. The very large apparent hysteresis is mainly caused by cycling opposing cantilevers through the instrument's entire dynamic range, and the fundamental imprecision inherent in use of the standard micrometers to calibrate the BMG. Laboratory mean hysteresis magnitudes for a polished cantilever typically range from 3 to 25 microstrain for 100 and 1000 microstrain relaxations on 1000 microstrain deflection loops intended to simulate typical field data. The error percentage is thought to remain fairly constant with deformation loop size, and is sufficiently small such that it can be safely ignored. The hysteresis effect can probably be reduced, and instrument stability improved by machining a small 90 degree cone in the cantilever in which a slightly larger mating cone on the base of the indentation button would reside. 5 refs. 26 figs., 1 tab

Capillary condensation, invasion percolation, hysteresis, and discrete memory

International Nuclear Information System (INIS)

Guyer, R.A.; McCall, K.R.

1996-01-01

A model of the capillary condensation process, i.e., of adsorption-desorption isotherms, having only pore-pore interactions is constructed. The model yields (1) hysteretic isotherms, (2) invasion percolation on desorption, and (3) hysteresis with discrete memory for interior chemical potential loops. All of these features are seen in experiment. The model is compared to a model with no pore-pore interactions (the Preisach model) and to a related model of interacting pore systems (the random field Ising model). The capillary condensation model differs from both. copyright 1996 The American Physical Society

Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions.

Science.gov (United States)

Zhang, Kun; Li, Huan-Huan; Grünberg, Peter; Li, Qiang; Ye, Sheng-Tao; Tian, Yu-Feng; Yan, Shi-Shen; Lin, Zhao-Jun; Kang, Shi-Shou; Chen, Yan-Xue; Liu, Guo-Lei; Mei, Liang-Mo

2015-09-21

Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. We find that the rectification magnetoresistance in Al/Ge Schottky heterojunctions is as large as 250% at room temperature, which is greatly enhanced as compared with the conventional magnetoresistance of 70%. The findings of rectification magnetoresistance open the way to the new nonmagnetic Ge-based spintronics devices of large rectification magnetoresistance at ambient temperature under the alternating-current due to the simultaneous implementation of the rectification and magnetoresistance in the same devices.

Non-local magnetoresistance in YIG/Pt nanostructures

Energy Technology Data Exchange (ETDEWEB)

Goennenwein, Sebastian T. B., E-mail: goennenwein@wmi.badw.de; Pernpeintner, Matthias; Gross, Rudolf; Huebl, Hans [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 München (Germany); Physik-Department, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany); Schlitz, Richard; Ganzhorn, Kathrin [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching (Germany); Physik-Department, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany); Althammer, Matthias [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meißner-Str. 8, 85748 Garching (Germany)

2015-10-26

We study the local and non-local magnetoresistance of thin Pt strips deposited onto yttrium iron garnet. The local magnetoresistive response, inferred from the voltage drop measured along one given Pt strip upon current-biasing it, shows the characteristic magnetization orientation dependence of the spin Hall magnetoresistance. We simultaneously also record the non-local voltage appearing along a second, electrically isolated, Pt strip, separated from the current carrying one by a gap of a few 100 nm. The corresponding non-local magnetoresistance exhibits the symmetry expected for a magnon spin accumulation-driven process, confirming the results recently put forward by Cornelissen et al. [“Long-distance transport of magnon spin information in a magnetic insulator at room temperature,” Nat. Phys. (published online 14 September 2015)]. Our magnetotransport data, taken at a series of different temperatures as a function of magnetic field orientation, rotating the externally applied field in three mutually orthogonal planes, show that the mechanisms behind the spin Hall and the non-local magnetoresistance are qualitatively different. In particular, the non-local magnetoresistance vanishes at liquid Helium temperatures, while the spin Hall magnetoresistance prevails.

Large, non-saturating magnetoresistance in WTe2.

Science.gov (United States)

Ali, Mazhar N; Xiong, Jun; Flynn, Steven; Tao, Jing; Gibson, Quinn D; Schoop, Leslie M; Liang, Tian; Haldolaarachchige, Neel; Hirschberger, Max; Ong, N P; Cava, R J

2014-10-09

Magnetoresistance is the change in a material's electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.

Simulations of magnetic hysteresis loops for dual layer recording media

Science.gov (United States)

Fal, T. J.; Plumer, M. L.; Whitehead, J. P.; Mercer, J. I.; van Ek, J.; Srinivasan, K.

2013-05-01

A Kinetic Monte-Carlo algorithm is applied to examine MH loops of dual-layer magnetic recording media at finite temperature and long time scales associated with typical experimental measurements. In contrast with standard micromagnetic simulations, which are limited to the ns-μs time regime, our approach allows for the direct calculation of magnetic configurations over periods from minutes to years. The model is used to fit anisotropy and coupling parameters to experimental data on exchange-coupled composite media which are shown to deviate significantly from standard micromagnetic results. Sensitivities of the loops to anisotropy, inter-layer exchange coupling, temperature, and sweep rate are examined.

Anomalous magnetoresistance in Fibonacci multilayers.

Energy Technology Data Exchange (ETDEWEB)

Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A. (Materials Science Division); (Universidade Federal do Rio Grande do Norte)

2012-01-01

We theoretically investigated magnetoresistance curves in quasiperiodic magnetic multilayers for two different growth directions, namely, [110] and [100]. We considered identical ferromagnetic layers separated by nonmagnetic layers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were included in our description of the magnetic energy: Zeeman, cubic anisotropy, bilinear coupling, and biquadratic coupling. The minimum energy was determined by the gradient method and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. By choosing spacers with a thickness such that biquadratic coupling is stronger than bilinear coupling, unusual behaviors for the magnetoresistance were observed: (i) for the [110] case, there is a different behavior for structures based on even and odd Fibonacci generations, and, more interesting, (ii) for the [100] case, we found magnetic field ranges for which the magnetoresistance increases with magnetic field.

Online optimized hysteresis-based steering feel model for steer-by-wire systems

Directory of Open Access Journals (Sweden)

Ahmet Kirli

2016-06-01

Full Text Available In rubber-wheeled road vehicles, the mechanical connection between steering wheel and front wheels provides steering-related feedback to the driver. The torque fed back to the driver through the steering linkages and steering wheel, which is called steering feel, helps the driver in controlling the vehicle. The torque feedback is reproduced via artificial methods in steer-by-wire systems due to the lack of mechanical connection. In this work, in order to minimize the physical workload and the lateral acceleration under the consideration of handling performance, optimization of a hysteresis-based steering feel has been studied. A 2-degree-of-freedom bicycle model based on the magic formula tire model has been used for simulations and hardware-in-the-loop experiments. A mathematical model is proposed in order to create an adaptive model-based optimization of the hysteresis parameters simultaneously while driving. A hardware-in-the-loop experimental setup has been used for the driving tests. The weave and the double-lane change tests have been performed with different drivers in order to demonstrate and quantify the optimization methods that are presented in this work.

An application of the time-step topological model for three-phase transformer no-load current calculation considering hysteresis

International Nuclear Information System (INIS)

Carrander, Claes; Mousavi, Seyed Ali; Engdahl, Göran

2017-01-01

In many transformer applications, it is necessary to have a core magnetization model that takes into account both magnetic and electrical effects. This becomes particularly important in three-phase transformers, where the zero-sequence impedance is generally high, and therefore affects the magnetization very strongly. In this paper, we demonstrate a time-step topological simulation method that uses a lumped-element approach to accurately model both the electrical and magnetic circuits. The simulation method is independent of the used hysteresis model. In this paper, a hysteresis model based on the first-order reversal-curve has been used. - Highlights: • A lumped-element method for modelling transformers i demonstrated. • The method can include hysteresis and arbitrarily complex geometries. • Simulation results for one power transformer are compared to measurements. • An analytical curve-fitting expression for static hysteresis loops is shown.

Magnetoresistance in RCo2 spin-fluctuation systems

International Nuclear Information System (INIS)

Gratz, E.; Nowotny, H.; Enser, J.; Bauer, E.; Hense, K.

2004-01-01

The effect of the spin fluctuations on the field and temperature dependence of the magnetoresistance in ScCo 2 and LuCo 2 was studied. The experimental data where explained assuming two competing mechanisms determining the magnetoresistance of these substances. One is the 'normal magnetoresistance' caused by the influence of the Lorentz force on conduction electron trajectories. The other is due to the suppression of the spin fluctuations caused by an external magnetic field. This interplay give rise to a pronounced drop of the magnetoresistance towards the lower temperature range

Tunneling anisotropic magnetoresistance driven by magnetic phase transition.

Science.gov (United States)

Chen, X Z; Feng, J F; Wang, Z C; Zhang, J; Zhong, X Y; Song, C; Jin, L; Zhang, B; Li, F; Jiang, M; Tan, Y Z; Zhou, X J; Shi, G Y; Zhou, X F; Han, X D; Mao, S C; Chen, Y H; Han, X F; Pan, F

2017-09-06

The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α'-FeRh-based junctions driven by the magnetic phase transition of α'-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α'-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α'-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics.Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α'-FeRh magnetic electrode.

Large magnetoresistance effect in nitrogen-doped silicon

Directory of Open Access Journals (Sweden)

Tao Wang

2017-05-01

Full Text Available In this work, we reported a large magnetoresistance effect in silicon by ion implantation of nitrogen atoms. At room temperature, the magnetoresistance of silicon reaches 125 % under magnetic field 1.7 T and voltage bias -80 V. By applying an alternating magnetic field with a frequency (f of 0.008 Hz, we find that the magnetoresistance of silicon is divided into f and 2f two signal components, which represent the linear and quadratic magnetoresistance effects, respectively. The analysis based on tuning the magnetic field and the voltage bias reveals that electric-field-induced space-charge effect plays an important role to enhance both the linear and quadratic magnetoresistance effects. Observation as well as a comprehensive explanation of large MR in silicon, especially based on semiconductor CMOS implantation technology, will be an important progress towards magnetoelectronic applications.

Thermally induced all-optical inverter and dynamic hysteresis loops in graphene oxide dispersions.

Science.gov (United States)

Melle, Sonia; Calderón, Oscar G; Egatz-Gómez, Ana; Cabrera-Granado, E; Carreño, F; Antón, M A

2015-11-01

We experimentally study the temporal dynamics of amplitude-modulated laser beams propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. Nonlinear refraction induced in the sample by thermal effects leads to both phase reversing of the transmitted signals and dynamic hysteresis in the input-output power curves. A theoretical model including beam propagation and thermal lensing dynamics reproduces the experimental findings.

Structural and magnetic properties of La0.7Sr0.3MnO3 ferromagnetic thin film grown on PMN-PT by sol–gel method

Directory of Open Access Journals (Sweden)

Jing Zhang

2017-08-01

Full Text Available We report the preparation of epitaxial La0.7Sr0.3MnO3 thin films grown on (001-oriented 0.72Pb(Mg1∕3Nb2∕3O3-0.28PbTiO3 substrates by the sol–gel technique. The phase structure, magnetic properties and magnetoresistance of the samples are investigated by using high solution X-ray diffraction, atomic force microscopy, physical property measurement system, respectively. The La0.7Sr0.3MnO3 thin films display a well-defined hysteresis loop and typical ferromagnetism behavior at lower temperature. High magnetoresistance at 5T of 42% appears at 227K for La0.7Sr0.3MnO3 thin film.

Large magnetoresistance in non-magnetic silver chalcogenides and new class of magnetoresistive compounds

Science.gov (United States)

Saboungi, Marie-Louis; Price, David C. L.; Rosenbaum, Thomas F.; Xu, Rong; Husmann, Anke

2001-01-01

The heavily-doped silver chalcogenides, Ag.sub.2+.delta. Se and Ag.sub.2+.delta. Te, show magnetoresistance effects on a scale comparable to the "colossal" magnetoresistance (CMR) compounds. Hall coefficient, magnetoconductivity, and hydrostatic pressure experiments establish that elements of narrow-gap semiconductor physics apply, but both the size of the effects at room temperature and the linear field dependence down to fields of a few Oersteds are surprising new features.

Huge magnetoresistance effect of highly oriented pyrolytic graphite

International Nuclear Information System (INIS)

Du Youwei; Wang Zhiming; Ni Gang; Xing Dingyu; Xu Qingyu

2004-01-01

Graphite is a quasi-two-dimensional semimetal. However, for usual graphite the magnetoresistance is not so high due to its small crystal size and no preferred orientation. Huge positive magnetoresistance up to 85300% at 4.2 K and 4950% at 300 K under 8.15 T magnetic field was found in highly oriented pyrolytic graphite. The mechanism of huge positive magnetoresistance is not only due to ordinary magnetoresistance but also due to magnetic-field-driven semimetal-insulator transition

Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals.

Science.gov (United States)

Lv, Yang-Yang; Zhang, Bin-Bin; Li, Xiao; Pang, Bin; Zhang, Fan; Lin, Da-Jun; Zhou, Jian; Yao, Shu-Hua; Chen, Y B; Zhang, Shan-Tao; Lu, Minghui; Liu, Zhongkai; Chen, Yulin; Chen, Yan-Feng

2016-05-27

Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~10(5)%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance. The stoichiometric WTe2 crystals have magnetoresistance as large as 3100% at 2 K and 9-Tesla magnetic field. However, only 71% and 13% magnetoresistance in the most non-stoichiometry (WTe1.80) and the highest Mo isovalent substitution samples (W0.7Mo0.3Te2) are observed, respectively. Analysis of the magnetic-field dependent magnetoresistance of non-stoichiometric WTe2 crystals substantiates that both the large electron-hole concentration asymmetry and decreased carrier mobility, induced by non-stoichiometry, synergistically lead to the decreased magnetoresistance. This work sheds more light on the origin of giant magnetoresistance observed in WTe2.

Assessing catchment connectivity using hysteretic loops

Science.gov (United States)

Davis, Jason; Masselink, Rens; Goni, Mikel; Gimenez, Rafael; Casali, Javier; Seeger, Manuel; Keesstra, Saskia

2017-04-01

Storm events mobilize large proportions of sediments in catchment systems. Therefore understanding catchment sediment dynamics throughout the continuity of storms and how initial catchment states act as controls on the transport of sediment to catchment outlets is important for effective catchment management. Sediment connectivity is a concept which can explain the origin, pathways and sinks of sediments within catchments (Baartman et al., 2013; Parsons et al., 2015; Masselink et al., 2016a,b; Mekonnen et al., 2016). However, sediment connectivity alone does not provide a practicable mechanism by which the catchment's initial state - and thus the location of entrained sediment in the sediment transport cascade - can be characterized. Studying the dynamic relationship between water discharge (Q) and suspended sediment (SS) at the catchment outlet can provide a valuable research tool to infer the likely source areas and flow pathways contributing to sediment transport because the relationship can be characterized by predictable hysteresis patterns. Hysteresis is observed when the sediment concentration associated with a certain flow rate is different depending on the direction in which the analysis is performed - towards the increase or towards the diminution of the flow. However, the complexity of the phenomena and factors which determine the hysteresis make its interpretation ambiguous. Previous work has described various types of hysteretic loops as well as the cause for the shape of the loop, mainly pointing to the origin of the sediments. The data set for this study comes from four experimental watersheds in Navarre (Spain), owned and maintained by the Government of Navarre. These experimental watersheds have been monitored and studied since 1996 (La Tejería and Latxaga) and 2001 (Oskotz principal and Oskotz woodland). La Tejería and Latxaga watersheds are similar to each other regarding size (approximately 200 ha), geology (marls and sandstones), soils (fine

Large magnetoresistance tunnelling through a magnetically modulated nanostructure

International Nuclear Information System (INIS)

Lu Maowang; Zhang Lide

2003-01-01

Based on a combination of an inhomogeneous magnetic field and a two-dimensional electron gas, we have constructed a giant magnetoresistance nanostructure, which can be realized experimentally by the deposition of two parallel ferromagnetic strips on top of a semiconductor heterostructure. We have theoretically studied the magnetoresistance for electrons tunnelling through this nanostructure. It is shown that there exists a significant transmission difference between the parallel and antiparallel magnetization configurations, which leads to a large magnetoresistance. It is also shown that the magnetoresistance ratio strongly depends not only on incident electronic energy but also on the ferromagnetic strips, and thus a much larger magnetoresistance ratio can be obtained by properly fabricating the ferromagnetic strips in the system

Vector hysteresis models

Czech Academy of Sciences Publication Activity Database

Krejčí, Pavel

1991-01-01

Roč. 2, - (1991), s. 281-292 ISSN 0956-7925 Keywords : vector hysteresis operator * hysteresis potential * differential inequality Subject RIV: BA - General Mathematics http://www.math.cas.cz/~krejci/b15p.pdf

Investigation of flip-flop effects in a linear analog comparator-with-hysteresis circuit

International Nuclear Information System (INIS)

Roche, N.J.H.; Buchner, S.P.; Warner, J.H.; McMorrow, D.; Roig, F.; Auriel, G.; Dusseau, L.; Boch, J.; Saigne, F.; Azais, B.

2013-01-01

The impact of the positive feedback loop on analog single event transient (ASET) shapes was investigated for a comparator- with-hysteresis circuit. Simulation based on previous developed ASET simulation tool is used to model the impact of the power supply voltage, the input voltage level and the injected energy. Simulation results show that these kinds of circuits are sensitive to flip-flop effects. This phenomenon occurs if the input voltage is in the hysteresis band range. In this case, simulations show that the ASET can latch the output into a non-desired state by changing the state of the circuit on his transfer characteristic curves. Laser experiments were conducted and show that the simulation outputs are in agreement with the experimental collected data. (authors)

Model for hysteresis in magnetostriction

International Nuclear Information System (INIS)

Sablik, M.J.; Jiles, D.C.

1988-01-01

The domain wall pinning model used previously by the authors to explain magnetic hysteresis and stress effects on magnetic hysteresis is used in conjunction with the Callen and Callen expression for magnetostriction λ to qualitatively explain magnetostriction hysteresis both with respect to magnetic intensity H and flux density B. The Callen and Callen form for the magnetostriction is used because it depends functionally on effective field H/sub e/ rather than M, and this produces hysteresis in λ vs B whereas λ = λ(M) does not. To our knowledge, this is the first time that magnetic hysteresis and magnetostriction hysteresis have been modeled simultaneously

Colossal Magnetoresistance Manganites and Related Prototype Devices

OpenAIRE

Liu, Yukuai; Yin, Yuewei; Li, Xiaoguang

2013-01-01

We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb:SrTiO3 pn junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions ...

Anisotropic magnetoresistance in a Fermi glass

International Nuclear Information System (INIS)

Ovadyahu, Z.; Physics Department, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84120)

1986-01-01

Insulating thin films of indium oxide exhibit negative, anisotropic magnetoresistance. The systematics of these results imply that the magnetoresistance mechanism may give different weight to the distribution of the localization lengths than that given by the hopping conductivity

Hysteresis of ferrogels magnetostriction

Energy Technology Data Exchange (ETDEWEB)

Zubarev, Andrey; Chirikov, Dmitry [Urals Federal University, 620000 Ekaterinburg (Russian Federation); Stepanov, Gennady [State Scientific Research Institute of Chemistry and Technology of Organoelement Compounds, 105118 Moscow (Russian Federation); Borin, Dmitry [Technische Universität Dresden, Magnetofluiddynamics, Measuring and Automation Technology, 01062 Dresden (Germany)

2017-06-01

We propose a theoretical model of magnetostriction hysteresis in soft magnetic gels filled by micronsized magnetizable particles. The hysteresis is explained by unification of the particles into linear chain-like aggregates while the field increasing and rupture of the chains when the field is decreased. - Highlights: • A theoretical model of magnetostriction hysteresis in magnetic gels is proposed. • Hysteresis is explained by the unification of the particles into chains and the rupture of this chains. • In the order of magnitude theoretical results are in agreement with the experimental one.

Magnetoresistance through spin-polarized p states

International Nuclear Information System (INIS)

Papanikolaou, Nikos

2003-01-01

We present a theoretical study of the ballistic magnetoresistance in Ni contacts using first-principles, atomistic, electronic structure calculations. In particular we investigate the role of defects in the contact region with the aim of explaining the recently observed spectacular magnetoresistance ratio. Our results predict that the possible presence of spin-polarized oxygen in the contact region could explain conductance changes by an order of magnitude. Electronic transport essentially occurs through spin-polarized oxygen p states, and this mechanism gives a much higher magnetoresistance than that obtained assuming clean atomically sharp domain walls alone

Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

Energy Technology Data Exchange (ETDEWEB)

Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: kerouad@fs-umi.ac.ma

2017-02-15

In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction J{sub s} on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined. - Highlights: • Phase diagrams of a ferromagnetic nanowire are examined by the Monte Carlo simulation. • Different types of the phase diagrams are obtained. • The effect of the random crystal field on the hysteresis loops is studied. • Single, double and para hysteresis regions are explicitly determined.

Magnetoresistance of magnetically doped ZnO films

Energy Technology Data Exchange (ETDEWEB)

Behan, A J; Mokhtari, A; Blythe, H J; Fox, A M; Gehring, G A [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Ziese, M, E-mail: G.A.Gehring@sheffield.ac.u [Division of Superconductivity and Magnetism, University of Leipzig, D-04103, Leipzig (Germany)

2009-08-26

Magnetoresistance measurements have been made at 5 K on doped ZnO thin films grown by pulsed laser deposition. ZnCoO, ZnCoAlO and ZnMnAlO samples have been investigated and compared to similar films containing no transition metal dopants. It is found that the Co-doped samples with a high carrier concentration have a small negative magnetoresistance, irrespective of their magnetic moment. On decreasing the carrier concentration, a positive contribution to the magnetoresistance appears and a further negative contribution. This second, negative contribution, which occurs at very low carrier densities, correlates with the onset of ferromagnetism due to bound magnetic polarons suggesting that the negative magnetoresistance results from the destruction of polarons by a magnetic field. An investigation of the anisotropic magnetoresistance showed that the orientation of the applied magnetic field, relative to the sample, had a large effect. The results for the ZnMnAlO samples showed less consistent trends.

Superconducting magnetoresistance in ferromagnet/superconductor/ferromagnet trilayers.

Science.gov (United States)

Stamopoulos, D; Aristomenopoulou, E

2015-08-26

Magnetoresistance is a multifaceted effect reflecting the diverse transport mechanisms exhibited by different kinds of plain materials and hybrid nanostructures; among other, giant, colossal, and extraordinary magnetoresistance versions exist, with the notation indicative of the intensity. Here we report on the superconducting magnetoresistance observed in ferromagnet/superconductor/ferromagnet trilayers, namely Co/Nb/Co trilayers, subjected to a parallel external magnetic field equal to the coercive field. By manipulating the transverse stray dipolar fields that originate from the out-of-plane magnetic domains of the outer layers that develop at coercivity, we can suppress the supercurrent of the interlayer. We experimentally demonstrate a scaling of the magnetoresistance magnitude that we reproduce with a closed-form phenomenological formula that incorporates relevant macroscopic parameters and microscopic length scales of the superconducting and ferromagnetic structural units. The generic approach introduced here can be used to design novel cryogenic devices that completely switch the supercurrent 'on' and 'off', thus exhibiting the ultimate magnetoresistance magnitude 100% on a regular basis.

Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core–shell structure

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Bahmad, L. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco)

2015-09-01

The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field. - Highlights: • Critical temperature increase when exchange interaction increasing in core-shell. • Hysteresis loop areas decrease at above transition temperature. • Magnetic coercive field decrease when crystal field increasing. • Magnetic coercive field increase when exchange interaction increasing.

Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions

OpenAIRE

Zhang, Kun; Li, Huan-huan; Grünberg, Peter; Li, Qiang; Ye, Sheng-tao; Tian, Yu-feng; Yan, Shi-shen; Lin, Zhao-jun; Kang, Shi-shou; Chen, Yan-xue; Liu, Guo-lei; Mei, and Liang-mo

2015-01-01

Magnetoresistance and rectification are two fundamental physical properties of heterojunctions and respectively have wide applications in spintronics devices. Being different from the well known various magnetoresistance effects, here we report a brand new large magnetoresistance that can be regarded as rectification magnetoresistance: the application of a pure small sinusoidal alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can generate a significant direct-current volt...

Colossal magnetoresistance manganites

Indian Academy of Sciences (India)

Keywords. Manganites; colossal magnetoresistance; strongly correlated electron systems; metal-insulator transitions and other electronic transitions; Jahn-Teller polarons and electron-phonon interaction.

Tunneling magnetoresistance in Si nanowires

KAUST Repository

Montes Muñoz, Enrique

2016-11-09

We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

Tracking Control of Shape-Memory-Alloy Actuators Based on Self-Sensing Feedback and Inverse Hysteresis Compensation

Directory of Open Access Journals (Sweden)

Shu-Hung Liu

2009-12-01

Full Text Available Shape memory alloys (SMAs offer a high power-to-weight ratio, large recovery strain, and low driving voltages, and have thus attracted considerable research attention. The difficulty of controlling SMA actuators arises from their highly nonlinear hysteresis and temperature dependence. This paper describes a combination of self-sensing and model-based control, where the model includes both the major and minor hysteresis loops as well as the thermodynamics effects. The self-sensing algorithm uses only the power width modulation (PWM signal and requires no heavy equipment. The method can achieve high-accuracy servo control and is especially suitable for miniaturized applications.

Resistivity dependence of magnetoresistance in Co/ZnO films.

Science.gov (United States)

Quan, Zhi-Yong; Zhang, Li; Liu, Wei; Zeng, Hao; Xu, Xiao-Hong

2014-01-06

We report the dependence of magnetoresistance effect on resistivity (ρ) in Co/ZnO films deposited by magnetron sputtering at different sputtering pressures with different ZnO contents. The magnitude of the resistivity reflects different carrier transport regimes ranging from metallic to hopping behaviors. Large room-temperature magnetoresistance greater than 8% is obtained in the resistivity range from 0.08 to 0.5 Ω · cm. The magnetoresistance value decreases markedly when the resistivity of the films is less than 0.08 Ω · cm or greater than 0.5 Ω · cm. When 0.08 Ω · cm magnetoresistance effect. When ρ > 0.5 Ω · cm, the spin-independent higher-order hopping (N > 2) comes into play and decreases the tunneling magnetoresistance value. For the samples with ρ magnetoresistance is mainly ascribed to the formation of percolation paths through interconnected elongated metallic Co particles. This observation is significant for the improvement of room-temperature magnetoresistance value for future spintronic devices.

Effect of External Economic-Field Cycle and Market Temperature on Stock-Price Hysteresis: Monte Carlo Simulation on the Ising Spin Model

Science.gov (United States)

Punya Jaroenjittichai, Atchara; Laosiritaworn, Yongyut

2017-09-01

In this work, the stock-price versus economic-field hysteresis was investigated. The Ising spin Hamiltonian was utilized as the level of ‘disagreement’ in describing investors’ behaviour. The Ising spin directions were referred to an investor’s intention to perform his action on trading his stock. The periodic economic variation was also considered via the external economic-field in the Ising model. The stochastic Monte Carlo simulation was performed on Ising spins, where the steady-state excess demand and supply as well as the stock-price were extracted via the magnetization. From the results, the economic-field parameters and market temperature were found to have significant effect on the dynamic magnetization and stock-price behaviour. Specifically, the hysteresis changes from asymmetric to symmetric loops with increasing market temperature and economic-field strength. However, the hysteresis changes from symmetric to asymmetric loops with increasing the economic-field frequency, when either temperature or economic-field strength is large enough, and returns to symmetric shape at very high frequencies. This suggests competitive effects among field and temperature factors on the hysteresis characteristic, implying multi-dimensional complicated non-trivial relationship among inputs-outputs. As is seen, the results reported (over extensive range) can be used as basis/guideline for further analysis/quantifying how economic-field and market-temperature affect the stock-price distribution on the course of economic cycle.

Giant magnetoresistance in CrFeMn alloys

International Nuclear Information System (INIS)

Xu, W.M.; Zheng, P.; Chen, Z.J.

1997-01-01

The electrical resistance and longitudinal magnetoresistance of Cr 75 (Fe x Mn 1-x ) 25 alloys, x=0.64, 0.72, are studied in the temperature range 1.5-270 K in applied field up to 7.5 T. The magnetoresistance is negative and strongly correlated with the spin reorientation. In the temperature range where the antiferromagnetic and ferromagnetic domains coexist, the samples display giant magnetoresistance which follows a H n -law at high field. (orig.)

Magnetic dipolar ordering and hysteresis of geometrically defined nanoparticle clusters

DEFF Research Database (Denmark)

Kure, Mathias; Beleggia, Marco; Frandsen, Cathrine

2017-01-01

Magnetic nanoparticle clusters have several biomedical and engineering applications, and revealing the basic interplay between particle configuration and magnetic properties is important for tuning the clusters for specific uses. Here, we consider the nanoparticles as macrospins and use computer...... of the polyhedra, the central moment relaxes along one of the principal axes and induces partial alignment of the surrounding moments. The resulting net moment is up to nearly four times that of the single moment added. Furthermore, we model quasi-static hysteresis loops for structures with and without a central...

Magnetic hysteresis scaling in thulium: Implication of irreversibility-related scaling for soliton wall motion in an Ising system

International Nuclear Information System (INIS)

Kobayashi, Satoru

2013-01-01

We report low-field magnetic hysteresis scaling in thulium with strong uniaxial anisotropy. A power-law hysteresis scaling with an exponent of 1.13±0.02 is found between hysteresis loss and remanent flux density of minor loops in the low-temperature ferrimagnetic phase. This exponent value is slightly lower than 1.25–1.4 observed previously for ferromagnets and helimagnets. Unlike spiral and/or Bloch walls with a finite transition width, typical for Dy, Tb, and Ho with planar anisotropy, a soliton wall with a sudden phase shift between neighboring domains may dominate in Tm due to its Ising-like character. The observations imply the presence of universality class of hysteresis scaling that depends on the type of magnetic anisotropy. - Highlights: ► We observe magnetic hysteresis scaling in thulium with a power law exponent of 1.13. ► Irreversibility of soliton walls dominates owing to its strong uniaxial anisotropy. ► The exponent is lower than those for Bloch wall and spiral wall. ► The results imply the presence of universality class that depends on the wall type.

A novel model of magnetorheological damper with hysteresis division

Science.gov (United States)

Yu, Jianqiang; Dong, Xiaomin; Zhang, Zonglun

2017-10-01

Due to the complex nonlinearity of magnetorheological (MR) behavior, the modeling of MR dampers is a challenge. A simple and effective model of MR damper remains a work in progress. A novel model of MR damper is proposed with force-velocity hysteresis division method in this study. A typical hysteresis loop of MR damper can be simply divided into two novel curves with the division idea. One is the backbone curve and the other is the branch curve. The exponential-family functions which capturing the characteristics of the two curves can simplify the model and improve the identification efficiency. To illustrate and validate the novel phenomenological model with hysteresis division idea, a dual-end MR damper is designed and tested. Based on the experimental data, the characteristics of the novel curves are investigated. To simplify the parameters identification and obtain the reversibility, the maximum force part, the non-dimensional backbone part and the non-dimensional branch part are derived from the two curves. The maximum force part and the non-dimensional part are in multiplication type add-rule. The maximum force part is dependent on the current and maximum velocity. The non-dominated sorting genetic algorithm II (NSGA II) based on the design of experiments (DOE) is employed to identify the parameters of the normalized shape functions. Comparative analysis is conducted based on the identification results. The analysis shows that the novel model with few identification parameters has higher accuracy and better predictive ability.

The nature of transport critical current hysteresis in HTSC: magnetic fields and high pressures. [Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Svistunov, V M; Yachenko, A.I. d' ; Tarenkov, V Yu [Donetsk Physico-Technical Inst., Ukrainian SSR (USSR)

1991-12-01

It was found that pressure has a strong influence on the critical current hysteresis loop of ceramics at H {proportional to} 10 kOe. The phenomenon is attributed to the critical current hysteresis of separate Josephson contacts and is due to the Abrikosov vortex density gradient within granules. The gradient defines both the sign and the value of the pinning current, whereas the sign of Meissner reversible surfaces current component is determined by the external field H direction. As a result the critical current of Josephson contacts defined by the total surface value depends on the magnetic prehistory of a sample. (orig.).

Temperature-Dependent Asymmetry of Anisotropic Magnetoresistance in Silicon p-n Junctions.

Science.gov (United States)

Yang, D Z; Wang, T; Sui, W B; Si, M S; Guo, D W; Shi, Z; Wang, F C; Xue, D S

2015-09-01

We report a large but asymmetric magnetoresistance in silicon p-n junctions, which contrasts with the fact of magnetoresistance being symmetric in magnetic metals and semiconductors. With temperature decreasing from 293 K to 100 K, the magnetoresistance sharply increases from 50% to 150% under a magnetic field of 2 T. At the same time, an asymmetric magnetoresistance, which manifests itself as a magnetoresistance voltage offset with respect to the sign of magnetic field, occurs and linearly increases with magnetoresistance. More interestingly, in contrast with other materials, the lineshape of anisotropic magnetoresistance in silicon p-n junctions significantly depends on temperature. As temperature decreases from 293 K to 100 K, the width of peak shrinks from 90° to 70°. We ascribe these novel magnetoresistance to the asymmetric geometry of the space charge region in p-n junction induced by the magnetic field. In the vicinity of the space charge region the current paths are deflected, contributing the Hall field to the asymmetric magnetoresistance. Therefore, the observed temperature-dependent asymmetry of magnetoresistance is proved to be a direct consequence of the spatial configuration evolution of space charge region with temperature.

Hysteresis behaviour of silver sputtered in different plasma atmospheres at constant flow rates

International Nuclear Information System (INIS)

Rizk, A.; Makar, L.N.; Rizk, N.S.; Shinoda, R.

1990-01-01

The effects of ion bombardment on sputtering behaviour of pure silver targets in inert and active gas atmospheres were investigated, using a dc planar magnetron sputtering system. The obtained current-voltage characteristics showed the formation of hysteresis loops without noticeable sharp transitions. Redeposited layers of silver nitride or silver oxide on the target surface when using nitrogen or oxygen in the glow discharge, residual ionization when using dry argon atmosphere were considered the main reasons for the occurrence of these loops. The results indicate that films of AgN x and AgO x can be deposited with controlled x in the range 0 ≤ x ≤ 1 using voltage control at constant gas flow rates. (author)

Large, Tunable Magnetoresistance in Nonmagnetic III-V Nanowires.

Science.gov (United States)

Li, Sichao; Luo, Wei; Gu, Jiangjiang; Cheng, Xiang; Ye, Peide D; Wu, Yanqing

2015-12-09

Magnetoresistance, the modulation of resistance by magnetic fields, has been adopted and continues to evolve in many device applications including hard-disk, memory, and sensors. Magnetoresistance in nonmagnetic semiconductors has recently raised much attention and shows great potential due to its large magnitude that is comparable or even larger than magnetic materials. However, most of the previous work focus on two terminal devices with large dimensions, typically of micrometer scales, which severely limit their performance potential and more importantly, scalability in commercial applications. Here, we investigate magnetoresistance in the impact ionization region in InGaAs nanowires with 20 nm diameter and 40 nm gate length. The deeply scaled dimensions of these nanowires enable high sensibility with less power consumption. Moreover, in these three terminal devices, the magnitude of magnetoresistance can be tuned by the transverse electric field controlled by gate voltage. Large magnetoresistance between 100% at room temperature and 2000% at 4.3 K can be achieved at 2.5 T. These nanoscale devices with large magnetoresistance offer excellent opportunity for future high-density large-scale magneto-electric devices using top-down fabrication approaches, which are compatible with commercial silicon platform.

Magnetic Hysteresis

CERN Document Server

Della Torre, Edward

2000-01-01

Understanding magnetic hysteresis is vitally important to the development of the science of magnetism as a whole and to the advancement of practical magnetic device applications. Magnetic Hysteresis, by acclaimed expert Edward Della Torre, presents a clear explanation of the connection between physical principles and phenomenological hysteresis. This comprehensive book offers a lucid analysis that enables the reader to save valuable time by reducing trial-and-error design. Dr. Della Torre uses physical principles to modify Preisach modeling and to describe the complex behavior of magnetic media. While Pretsach modeling is a useful mathematical tool, its congruency and deletion properties present limitations to accurate descriptions of magnetic materials. Step-by-step, this book describes the modifications that can overcome these limitations. Special attention is given to the use of feedback around a Preisach transducer to remove the congruency restriction, and to the use of accommodation and aftereffect model...

Influence of applied compressive stress on the hysteresis curves and magnetic domain structure of grain-oriented transverse Fe-3%Si steel

International Nuclear Information System (INIS)

Perevertov, O; Schäfer, R

2012-01-01

The influence of an applied compressive stress on the hysteresis curve and domain structure in conventional (1 1 0) [0 0 1] Fe-3%Si steel cut transverse to the rolling direction is studied. Quasistatic hysteresis loops under compressive stress up to 75 MPa were measured. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of stress. It is shown that the bulk hysteresis loop can be described with a good accuracy by the action of an effective field, which is the product of the stress and a function of magnetization. Domain observations have shown that the reasons for the effective field are demagnetizing fields due to the disappearance of supplementary domains along [0 1 0] and [1 0 0] at low fields and different domain systems in different grains at moderate fields. The latter are caused by differences in grain sensitivity to stress depending on the degree of misorientation. A decrease in the effective field above 1 T is connected with a transformation of all grains into the same domain system—the column pattern. (paper)

Prandtl-Ishlinskii hysteresis models for complex time dependent hysteresis nonlinearities

Czech Academy of Sciences Publication Activity Database

Al Janaideh, M.; Krejčí, Pavel

2012-01-01

Roč. 407, č. 9 (2012), s. 1365-1367 ISSN 0921-4526 R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : complex hysteresis * time dependent hysteresis * Prandtl-Ishlinskii model Subject RIV: BA - General Mathematics Impact factor: 1.327, year: 2012 http://www.sciencedirect.com/science/article/pii/S092145261100932X

Extremely large magnetoresistance in few-layer graphene/boron-nitride heterostructures.

Science.gov (United States)

Gopinadhan, Kalon; Shin, Young Jun; Jalil, Rashid; Venkatesan, Thirumalai; Geim, Andre K; Castro Neto, Antonio H; Yang, Hyunsoo

2015-09-21

Understanding magnetoresistance, the change in electrical resistance under an external magnetic field, at the atomic level is of great interest both fundamentally and technologically. Graphene and other two-dimensional layered materials provide an unprecedented opportunity to explore magnetoresistance at its nascent stage of structural formation. Here we report an extremely large local magnetoresistance of ∼2,000% at 400 K and a non-local magnetoresistance of >90,000% in an applied magnetic field of 9 T at 300 K in few-layer graphene/boron-nitride heterostructures. The local magnetoresistance is understood to arise from large differential transport parameters, such as the carrier mobility, across various layers of few-layer graphene upon a normal magnetic field, whereas the non-local magnetoresistance is due to the magnetic field induced Ettingshausen-Nernst effect. Non-local magnetoresistance suggests the possibility of a graphene-based gate tunable thermal switch. In addition, our results demonstrate that graphene heterostructures may be promising for magnetic field sensing applications.

Systematic study of doping dependence on linear magnetoresistance in p-PbTe

International Nuclear Information System (INIS)

Schneider, J. M.; Chitta, V. A.; Oliveira, N. F.; Peres, M. L.; Castro, S. de; Soares, D. A. W.; Wiedmann, S.; Zeitler, U.; Abramof, E.; Rappl, P. H. O.; Mengui, U. A.

2014-01-01

We report on a large linear magnetoresistance effect observed in doped p-PbTe films. While undoped p-PbTe reveals a sublinear magnetoresistance, p-PbTe films doped with BaF 2 exhibit a transition to a nearly perfect linear magnetoresistance behaviour that is persistent up to 30 T. The linear magnetoresistance slope ΔR/ΔB is to a good approximation, independent of temperature. This is in agreement with the theory of Quantum Linear Magnetoresistance. We also performed magnetoresistance simulations using a classical model of linear magnetoresistance. We found that this model fails to explain the experimental data. A systematic study of the doping dependence reveals that the linear magnetoresistance response has a maximum for small BaF 2 doping levels and diminishes rapidly for increasing doping levels. Exploiting the huge impact of doping on the linear magnetoresistance signal could lead to new classes of devices with giant magnetoresistance behavior.

Large linear magnetoresistance and magnetothermopower in layered SrZnSb$_2$

OpenAIRE

Wang, Kefeng; Petrovic, C.

2016-01-01

We report the large linear magnetoresistance ($\\sim 300\\%$ in 9 T field at 2 K) and magnetothermopower in layered SrZnSb$_2$ crystal with quasi-two-dimensional Sb layers. A crossover from the semiclassical parabolic field dependent magnetoresistance to linear field dependent magnetoresistance with increasing magnetic field is observed. The magnetoresistance behavior can be described very well by combining the semiclassical cyclotron contribution and the quantum limit magnetoresistance. Magnet...

Magnetoresistance in terbium and holmium single crystals

International Nuclear Information System (INIS)

Singh, R.L.; Jericho, M.H.; Geldart, D.J.W.

1976-01-01

The longitudinal magnetoresistance of single crystals of terbium and holmium metals in their low-temperature ferromagnetic phase has been investigated in magnetic fields up to 80 kOe. Typical magnetoresistance isotherms exhibit a minimum which increases in depth and moves to higher fields as the temperature increases. The magnetoresistance around 1 0 K, where inelastic scattering is negligible, has been interpreted as the sum of a negative contribution due to changes in the domain structure and a positive contribution due to normal magnetoresistance. At higher temperatures, a phenomenological approach has been developed to extract the inelastic phonon and spin-wave components from the total measured magnetoresistance. In the temperature range 4--20 0 K (approximately), the phonon resistivity varies as T 3 . 7 for all samples. Approximate upper and lower bounds have been placed on the spin-wave resistivity which is also found to be described by a simple power law in this temperature range. The implications of this result for theoretical treatments of spin-wave resistivity due to s-f exchange interactions are considered. It is concluded that the role played by the magnon energy gap is far less transparent than previously suggested

Characterizing piezoscanner hysteresis and creep using optical levers and a reference nanopositioning stage

International Nuclear Information System (INIS)

Xie, H.; Regnier, S.; Rakotondrabe, M.

2009-01-01

A method using atomic force microscope (AFM) optical levers and a reference nanopositioning stage has been developed to characterize piezoscanner hysteresis and creep. The piezoscanner is fixed on a closed-loop nanopositioning stage, both of which have the same arrangement on each axis of the three spatial directions inside the AFM-based nanomanipulation system. In order to achieve characterization, the optical lever is used as a displacement sensor to measure the relative movement between the nanopositioning stage and the piezoscanner by lateral tracking a well-defined slope with the tapping mode of the AFM cantilever. This setup can be used to estimate a piezoscanner's voltage input with a reference displacement from the nanopositioning stage. The hysteresis and creep were accurately calibrated by the method presented, which use the current setup of the AFM-based nanomanipulation system without any modification or additional devices.

Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress

International Nuclear Information System (INIS)

Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

1992-01-01

The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters

Spin-flip induced magnetoresistance in positionally disordered organic solids.

Science.gov (United States)

Harmon, N J; Flatté, M E

2012-05-04

A model for magnetoresistance in positionally disordered organic materials is presented and solved using percolation theory. The model describes the effects of spin dynamics on hopping transport by considering changes in the effective density of hopping sites, a key quantity determining the properties of percolative transport. Faster spin-flip transitions open up "spin-blocked" pathways to become viable conduction channels and hence produce magnetoresistance. Features of this percolative magnetoresistance can be found analytically in several regimes, and agree with previous measurements, including the sensitive dependence of the magnetic-field dependence of the magnetoresistance on the ratio of the carrier hopping time to the hyperfine-induced carrier spin precession time. Studies of magnetoresistance in known systems with controllable positional disorder would provide an additional stringent test of this theory.

The magnetoresistance of sub-micron Fe wires

Science.gov (United States)

Blundell, S. J.; Shearwood, C.; Gester, M.; Baird, M. J.; Bland, J. A. C.; Ahmed, H.

1994-07-01

A novel combination of electron- and ion-beam lithography has been used to prepare Fe gratings with wire widths of 0.5 μm and wire separations in the range 0.5-4 μm from an Fe/GaAs (001) film of thickness 25 nm. With an in-plane magnetic field applied perpendicular to the length of the wires, a harder magnetisation loop is observed using the magneto-optic Kerr effect (MOKE), compared with that observed in the unprocessed film. We observe a strong effect in the magnetoresistance (MR) when the magnetic field is applied transverse to the wires. It is believed that this effect originates from the highly non-uniform demagnetising field in each wire of the grating. These results demonstrate that the combination of MOKE and MR measurements can provide important information about the magnetisation reversal processes in magnetic gratings and can be used to understand the effect of shape anisotropy on magnetic properties.

Computing with volatile memristors: an application of non-pinched hysteresis

Science.gov (United States)

Pershin, Y. V.; Shevchenko, S. N.

2017-02-01

The possibility of in-memory computing with volatile memristive devices, namely, memristors requiring a power source to sustain their memory, is demonstrated theoretically. We have adopted a hysteretic graphene-based field emission structure as a prototype of a volatile memristor, which is characterized by a non-pinched hysteresis loop. A memristive model of the structure is developed and used to simulate a polymorphic circuit implementing stateful logic gates, such as the material implication. Specific regions of parameter space realizing useful logic functions are identified. Our results are applicable to other realizations of volatile memory devices, such as certain NEMS switches.

Magnetoresistive multilayers deposited on the AAO membranes

International Nuclear Information System (INIS)

Malkinski, Leszek M.; Chalastaras, Athanasios; Vovk, Andriy; Jung, Jin-Seung; Kim, Eun-Mee; Jun, Jong-Ho; Ventrice, Carl A.

2005-01-01

Silicon and GaAs wafers are the most commonly used substrates for deposition of giant magnetoresistive (GMR) multilayers. We explored a new type of a substrate, prepared electrochemically by anodization of aluminum sheets, for deposition of GMR multilayers. The surface of this AAO substrate consists of nanosized hemispheres organized in a regular hexagonal array. The current applied along the substrate surface intersects many magnetic layers in the multilayered structure, which results in enhancement of giant magnetoresistance effect. The GMR effect in uncoupled Co/Cu multilayers was significantly larger than the magnetoresistance of similar structures deposited on Si

New type magnetoresistance in Co/Si systems

International Nuclear Information System (INIS)

Honda, S.; Ishikawa, T.; Takai, K.; Mitarai, Y.; Harada, H.

2005-01-01

The magnetoresistance (MR) properties in both the sputter-deposited Co/Si multilayers and the system consisting of Co evaporated on the anodized Si have been examined. In the Co/Si multilayers, at room temperature both the sharp ordinary magnetoresistance (OMR) and the negative granular-type giant magnetoresistance (GMR) appear, while at low temperatures only the large OMR of about 3.5% is observed for in-plane field. In the Co/anodized-Si system, at room temperature the MR is negligibly small, while it increases steeply with decreasing temperature and very large OMR of about 22% is obtained at 110 K for perpendicular field

Local hysteresis and grain size effect in Pb(Mg1/3Nb2/3)O3- PbTiO3 thin films

Science.gov (United States)

Shvartsman, V. V.; Emelyanov, A. Yu.; Kholkin, A. L.; Safari, A.

2002-07-01

The local piezoelectric properties of relaxor ferroelectric films of solid solutions 0.9Pb(Mg1/3Nb2/3)O3- 0.1PbTiO3 were investigated by scanning force microscopy (SFM) in a piezoelectric contact mode. The piezoelectric hysteresis loops were acquired in the interior of grains of different sizes. A clear correlation between the values of the effective piezoelectric coefficients, deff, and the size of the respective grains is observed. Small grains exhibit slim piezoelectric hysteresis loops with low remanent deff, whereas relatively strong piezoelectric activity is characteristic of larger grains. Part of the grains (approx20-25%) is strongly polarized without application of a dc field. The nature of both phenomena is discussed in terms of the internal bias field and grain size effects on the dynamics of nanopolar clusters.

Semiclassical theory of magnetoresistance in positionally disordered organic semiconductors

Science.gov (United States)

Harmon, N. J.; Flatté, M. E.

2012-02-01

A recently introduced percolative theory of unipolar organic magnetoresistance is generalized by treating the hyperfine interaction semiclassically for an arbitrary hopping rate. Compact analytic results for the magnetoresistance are achievable when carrier hopping occurs much more frequently than the hyperfine field precession period. In other regimes the magnetoresistance can be straightforwardly evaluated numerically. Slow and fast hopping magnetoresistance are found to be uniquely characterized by their line shapes. We find that the threshold hopping distance is analogous a phenomenological two-site model's branching parameter, and that the distinction between slow and fast hopping is contingent on the threshold hopping distance.

Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor chromium arsenide.

Science.gov (United States)

Niu, Q; Yu, W C; Yip, K Y; Lim, Z L; Kotegawa, H; Matsuoka, E; Sugawara, H; Tou, H; Yanase, Y; Goh, Swee K

2017-06-05

In conventional metals, modification of electron trajectories under magnetic field gives rise to a magnetoresistance that varies quadratically at low field, followed by a saturation at high field for closed orbits on the Fermi surface. Deviations from the conventional behaviour, for example, the observation of a linear magnetoresistance, or a non-saturating magnetoresistance, have been attributed to exotic electron scattering mechanisms. Recently, linear magnetoresistance has been observed in many Dirac materials, in which the electron-electron correlation is relatively weak. The strongly correlated helimagnet CrAs undergoes a quantum phase transition to a nonmagnetic superconductor under pressure. Here we observe, near the magnetic instability, a large and non-saturating quasilinear magnetoresistance from the upper critical field to 14 T at low temperatures. We show that the quasilinear magnetoresistance may arise from an intricate interplay between a nontrivial band crossing protected by nonsymmorphic crystal symmetry and strong magnetic fluctuations.

The magnetoresistivity of some rare-earth metals

International Nuclear Information System (INIS)

Webber, G.D.

1978-10-01

The thesis describes measurements of the low temperature transverse magnetoresistivities of single crystals of rare-earth metals in magnetic fields up to 8 Tesla. A general introduction to the rare-earths, their magnetic properties and a review of the basic theory and mechanism of magnetoresistivity is given. Details of the crystal structure, growth of single crystals and sample mounting method follow. The experimental equipment and measuring techniques are then described. The low temperature transverse magnetoresistivity of polycrystalline lanthanum and single crystal praseodymium for the temperature range 4.2 - 30K is measured. The separation of the spin-disorder and Fermi-surface orbital effect contributions are described and the theoretical and experimental spin-disorder values compared. Magnetoresistivity measurements for neodymium single crystals (4.2 - 30K) are compared with the magnetic properties determined from neutron diffraction studies. Results for gadolinium single crystals (4.2 - 200K) are compared for two different impurity levels and with previous work. (UK)

Magnetoresistance and magnetostriction of Ni81Fe19 and Co90Fe10 mono- and bilayer films

International Nuclear Information System (INIS)

Sahingoz, R.; Hollingworth, M.P.; Gibbs, M.R.J.; Murdoch, S.J.

2005-01-01

Monolayer and bilayer films of Ni 81 Fe 19 , Co 90 Fe 10 , Co 90 Fe 10 /Ni 81 Fe 19 , and Ni 81 Fe 19 /Co 90 Fe 10 have been grown on thermally oxidized Si. The magnetoresistance (MR) of the samples was measured as a function of applied DC magnetic field, using a four-point probe method. The magnetostriction constant, λ s , was derived from the change of anisotropy field as a function of strain. The dependence of the MR on different combinations of film layers was investigated. The magnetoresistance of the bilayers changed dramatically upon reversal of the layer order. The mono- and bilayer samples with the same material on top of the substrate showed similar MR loop shapes. However, the saturation fields of the bilayers were larger than those for the monolayers. The magnetostriction of all samples was negative. We discuss the consequences for the study and optimization of spin-valve devices

Mutual influence between current-induced giant magnetoresistance and radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2DES

OpenAIRE

Samaraweera, R. L.; Liu, H.-C.; Wang, Z.; Reichl, C.; Wegscheider, W.; Mani, R. G.

2017-01-01

Radiation-induced magnetoresistance oscillations are examined in the GaAs/AlGaAs 2D system in the regime where an observed concurrent giant magnetoresistance is systematically varied with a supplementary dc-current, I dc . The I dc tuned giant magnetoresistance is subsequently separated from the photo-excited oscillatory resistance using a multi-conduction model in order to examine the interplay between the two effects. The results show that the invoked multiconduction model describes the obs...

Magnetoresistance in molybdenite (MoS2) crystals

International Nuclear Information System (INIS)

Chakraborty, B.R.; Dutta, A.K.

1975-01-01

The principal magnetoresistance ratios of molybdenite (MoS 2 ), the naturally occurring semiconducting crystal, have been investigated at magnetic fields ranging from 4.5 KOe and within the temperature range 300 0 K to 700 0 K. Unlike some previous observations, magnetoresistance has been found to be negative. (author)

Spin Hall magnetoresistance at high temperatures

International Nuclear Information System (INIS)

Uchida, Ken-ichi; Qiu, Zhiyong; Kikkawa, Takashi; Iguchi, Ryo; Saitoh, Eiji

2015-01-01

The temperature dependence of spin Hall magnetoresistance (SMR) in Pt/Y 3 Fe 5 O 12 (YIG) bilayer films has been investigated in a high temperature range from room temperature to near the Curie temperature of YIG. The experimental results show that the magnitude of the magnetoresistance ratio induced by the SMR monotonically decreases with increasing the temperature and almost disappears near the Curie temperature. We found that, near the Curie temperature, the temperature dependence of the SMR in the Pt/YIG film is steeper than that of a magnetization curve of the YIG; the critical exponent of the magnetoresistance ratio is estimated to be 0.9. This critical behavior of the SMR is attributed mainly to the temperature dependence of the spin-mixing conductance at the Pt/YIG interface

Magnetoresistance effect in a both magnetically and electrically modulated nanostructure

International Nuclear Information System (INIS)

Lu, Mao-Wang; Yang, Guo-Jian

2007-01-01

We propose a magnetoresistance device in a both magnetically and electrically modulated two-dimensional electron gas, which can be realized experimentally by the deposition, on the top and bottom of a semiconductor heterostructure, of two parallel metallic ferromagnetic strips under an applied voltage. It is shown that a considerable magnetoresistance effect can be achieved in such a device due to the significant transmission difference for electrons through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio depends strongly on the applied voltage to the stripe in the device. These interesting properties may provide an alternative scheme to realize magnetoresistance effect in hybrid ferromagnetic/semiconductor nanosystems, and this system may be used as a voltage-tunable magnetoresistance device

Neural networks dynamic hysteresis model for piezoceramic actuator based on hysteresis operator of first-order differential equation

International Nuclear Information System (INIS)

Dang Xuanju; Tan Yonghong

2005-01-01

A new neural networks dynamic hysteresis model for piezoceramic actuator is proposed by combining the Preisach model with diagonal recurrent neural networks. The Preisach model is based on elementary rate-independent operators and is not suitable for modeling piezoceramic actuator across a wide frequency band because of the rate-dependent hysteresis characteristic of the piezoceramic actuator. The structure of the developed model is based on the structure of the Preisach model, in which the rate-independent relay hysteresis operators (cells) are replaced by the rate-dependent hysteresis operators of first-order differential equation. The diagonal recurrent neural networks being modified by an adjustable factor can be used to model the hysteresis behavior of the pizeoceramic actuator because its structure is similar to the structure of the modified Preisach model. Therefore, the proposed model not only possesses that of the Preisach model, but also can be used for describing its dynamic hysteresis behavior. Through the experimental results of both the approximation and the prediction, the effectiveness of the neural networks dynamic hysteresis model for the piezoceramic actuator is demonstrated

Understanding Unemployment Hysteresis

DEFF Research Database (Denmark)

Møller, Niels Framroze

What explains the persistence of unemployment? The literature on hysteresis, which is based on unit root testing in autoregressive models, consists of a vast number of univariate studies, i.e. that analyze unemployment series in isolation, but few multivariate analyses that focus on the sources...... of hysteresis. As a result, this question remains largely unanswered. This paper presents a multivariate econometric framework for analyzing hysteresis, which allows one to test different hypotheses about non-stationarity of unemployment against one another. For example, whether this is due to a persistently...... to UK quarterly data on prices, wages, output, unemployment and crude oil prices, suggests that, for the period 1988 up to the onset of the …financial crisis, the non-stationarity of UK unemployment cannot be explained as a result of slow adjustment, including sluggish wage formation as emphasized...

Effect of separated layer thickness on magnetoresistance and magnetic properties of Co/Dy/Co and Ni/Dy/Ni film systems

Science.gov (United States)

Shabelnyk, T. M.; Shutylieva, O. V.; Vorobiov, S. I.; Pazukha, I. M.; Chornous, A. M.

2018-01-01

Co(5 nm)/Dy(tDy)/Co(20 nm)/S and Ni(5 nm)/Dy(tDy)/Ni(20 nm)/S trilayer films are prepared by electron-beam sputtering to investigate the influence of dysprosium layer thickness (tDy) and thermal annealing on the crystal structure, magnetoresistance (MR) and magnetic properties of thin films. The thickness of Dy layer changed in the range from 1 nm to 20 nm. The samples annealed for 20 min at 700 K. Electron diffraction patterns reveal that the as-deposited and annealed systems Co/Dy/Co and Ni/Dy/Ni had fcc-Co + hcp-Dy and fcc-Ni + hcp-Dy phase state, respectively. It is also shown that at the tDy = 15 nm the transition from amorphous to crystalline structures of Dy layer is observed. An increase in the Dy layer thickness results in changes in the MR and magnetic properties of the trilayer systems. It is shown that MR is most thermally stable against annealing to 700 K at tDy = 15 nm for Co/Dy/Co as well as for Ni/Dy/Ni. For tDy = 15 nm the, value of MR for both system increases by two times compared to those of pure ferromagnetic (FM) samples. The coercivity (Bc), remanent (Mr) and saturation (Ms) magnetization of the in-plain magnetization hysteresis loops are related to the Dy layer thickness too. The coercivity depends on the FM materials type and diffusion processes at the layer boundary. Accordingly, Mr and Ms are reduced with tDy increasing before and after annealing for both trilayer systems.

Dynamic hysteresis of a uniaxial superparamagnet: Semi-adiabatic approximation

International Nuclear Information System (INIS)

Poperechny, I.S.; Raikher, Yu.L.; Stepanov, V.I.

2014-01-01

The semi-adiabatic theory of magnetic response of a uniaxial single-domain ferromagnetic particle is presented. The approach is developed in the context of the kinetic theory and allows for any orientation of the external field. Within this approximation, the dynamic magnetic hysteresis loops in an ac field are calculated. It is demonstrated that they very closely resemble those obtained by the full kinetic theory. The behavior of the effective coercive force is analyzed in detail, and for it a simple formula is proposed. This relation accounts not only for the temperature behavior of the coercive force, as the previous ones do, but also yields the dependence on the frequency and amplitude of the applied field

Room temperature electrically tunable rectification magnetoresistance in Ge-based Schottky devices.

Science.gov (United States)

Huang, Qi-Kun; Yan, Yi; Zhang, Kun; Li, Huan-Huan; Kang, Shishou; Tian, Yu-Feng

2016-11-23

Electrical control of magnetotransport properties is crucial for device applications in the field of spintronics. In this work, as an extension of our previous observation of rectification magnetoresistance, an innovative technique for electrical control of rectification magnetoresistance has been developed by applying direct current and alternating current simultaneously to the Ge-based Schottky devices, where the rectification magnetoresistance could be remarkably tuned in a wide range. Moreover, the interface and bulk contribution to the magnetotransport properties has been effectively separated based on the rectification magnetoresistance effect. The state-of-the-art electrical manipulation technique could be adapt to other similar heterojunctions, where fascinating rectification magnetoresistance is worthy of expectation.

The effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors

International Nuclear Information System (INIS)

Zhao Jun-Qing; Ding Meng; Zhang Tian-You; Zhang Ning-Yu; Pang Yan-Tao; Ji Yan-Ju; Chen Ying; Wang Feng-Xiang; Fu Gang

2012-01-01

We investigated the effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors. A Lorentz-type magnetoresistance is obtained from spin-orbit coupling-dependent spin precession under the condition of a space-charge-limited current. The magnetoresistance depends on the initial spin orientation of the electron with respect to the hole in electron—hole pairs, and the increasing spin-orbit coupling slows down the change in magnetoresistance with magnetic field. The field dependence, the sign and the saturation value of the magnetoresistance are composite effects of recombination and dissociation rate constants of singlet and triplet electron—hole pairs. The simulated magnetoresistance shows good consistency with the experimental results. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Scanning of Adsorption Hysteresis In Situ with Small Angle X-Ray Scattering.

Directory of Open Access Journals (Sweden)

Athanasios Ch Mitropoulos

Full Text Available Everett's theorem-6 of the domain theory was examined by conducting adsorption in situ with small angle x-ray scattering (SAXS supplemented by the contrast matching technique. The study focuses on the spectrum differences of a point to which the system arrives from different scanning paths. It is noted that according to this theorem at a common point the system has similar macroscopic properties. Furthermore it was examined the memory string of the system. We concluded that opposite to theorem-6: a at a common point the system can reach in a finite (not an infinite number of ways, b a correction for the thickness of the adsorbed film prior to capillary condensation is necessary, and c the scattering curves although at high-Q values coincide, at low-Q values are different indicating different microscopic states. That is, at a common point the system holds different metastable states sustained by hysteresis effects. These metastable states are the ones which highlight the way of a system back to a return point memory (RPM. Entering the hysteresis loop from different RPMs different histories are implanted to the paths toward the common point. Although in general the memory points refer to relaxation phenomena, they also constitute a characteristic feature of capillary condensation. Analogies of the no-passing rule and the adiabaticity assumption in the frame of adsorption hysteresis are discussed.

Scanning of Adsorption Hysteresis In Situ with Small Angle X-Ray Scattering

Science.gov (United States)

Mitropoulos, Athanasios Ch.; Favvas, Evangelos P.; Stefanopoulos, Konstantinos L.; Vansant, Etienne F.

2016-01-01

Everett’s theorem-6 of the domain theory was examined by conducting adsorption in situ with small angle x-ray scattering (SAXS) supplemented by the contrast matching technique. The study focuses on the spectrum differences of a point to which the system arrives from different scanning paths. It is noted that according to this theorem at a common point the system has similar macroscopic properties. Furthermore it was examined the memory string of the system. We concluded that opposite to theorem-6: a) at a common point the system can reach in a finite (not an infinite) number of ways, b) a correction for the thickness of the adsorbed film prior to capillary condensation is necessary, and c) the scattering curves although at high-Q values coincide, at low-Q values are different indicating different microscopic states. That is, at a common point the system holds different metastable states sustained by hysteresis effects. These metastable states are the ones which highlight the way of a system back to a return point memory (RPM). Entering the hysteresis loop from different RPMs different histories are implanted to the paths toward the common point. Although in general the memory points refer to relaxation phenomena, they also constitute a characteristic feature of capillary condensation. Analogies of the no-passing rule and the adiabaticity assumption in the frame of adsorption hysteresis are discussed. PMID:27741263

Effect of quantum tunneling on spin Hall magnetoresistance.

Science.gov (United States)

Ok, Seulgi; Chen, Wei; Sigrist, Manfred; Manske, Dirk

2017-02-22

We present a formalism that simultaneously incorporates the effect of quantum tunneling and spin diffusion on the spin Hall magnetoresistance observed in normal metal/ferromagnetic insulator bilayers (such as Pt/Y 3 Fe 5 O 12 ) and normal metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of magnetization influences the magnetoresistance of the normal metal. In the normal metal side the spin diffusion is known to affect the landscape of the spin accumulation caused by spin Hall effect and subsequently the magnetoresistance, while on the ferromagnet side the quantum tunneling effect is detrimental to the interface spin current which also affects the spin accumulation. The influence of generic material properties such as spin diffusion length, layer thickness, interface coupling, and insulating gap can be quantified in a unified manner, and experiments that reveal the quantum feature of the magnetoresistance are suggested.

Temperature dependence of magnetoresistance in lanthanum manganite ceramics

International Nuclear Information System (INIS)

Gubkin, M.K.; Zalesskii, A.V.; Perekalina, T.M.

1996-01-01

Magnetoresistivity in the La0.9Na0.1Mn0.9(V,Co)0.1O3 and LaMnO3+δ ceramics was studied. The temperature dependence of magnetoresistance in these specimens was found to differ qualitatively from that in the La0.9Na0.1MnO3 single crystal (the magnetoresistance value remains rather high throughout the measurement range below the Curie temperature), with the maximum values being about the same (20-40% in the field of 20 kOe). Previously published data on magnetization, high frequency magnetic susceptibility, and local fields at the 139La nuclei of the specimens with similar properties attest to their magnetic inhomogeneity. The computation of the conductivity of the nonuniformly ordered lanthanum manganite was performed according to the mean field theory. The calculation results allow one to interpret qualitatively various types of experimental temperature dependences of magnetoresistance

Hopping magnetotransport via nonzero orbital momentum states and organic magnetoresistance.

Science.gov (United States)

Alexandrov, Alexandre S; Dediu, Valentin A; Kabanov, Victor V

2012-05-04

In hopping magnetoresistance of doped insulators, an applied magnetic field shrinks the electron (hole) s-wave function of a donor or an acceptor and this reduces the overlap between hopping sites resulting in the positive magnetoresistance quadratic in a weak magnetic field, B. We extend the theory of hopping magnetoresistance to states with nonzero orbital momenta. Different from s states, a weak magnetic field expands the electron (hole) wave functions with positive magnetic quantum numbers, m>0, and shrinks the states with negative m in a wide region outside the point defect. This together with a magnetic-field dependence of injection/ionization rates results in a negative weak-field magnetoresistance, which is linear in B when the orbital degeneracy is lifted. The theory provides a possible explanation of a large low-field magnetoresistance in disordered π-conjugated organic materials.

Effect of applied tensile stress on the hysteresis curve and magnetic domain structure of grain-oriented transverse Fe-3%Si steel

Czech Academy of Sciences Publication Activity Database

Perevertov, Oleksiy; Thielsch, J.; Schäfer, R.

2015-01-01

Roč. 385, Jul (2015), 358-367 ISSN 0304-8853 R&D Projects: GA ČR GA13-18993S Institutional support: RVO:68378271 Keywords : magnetic domains * magnetization process * magnetoelasticity * hysteresis loops * tension * Kerr microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.357, year: 2015

Colossal magnetoresistance in manganites and related prototype devices

International Nuclear Information System (INIS)

Liu Yu-Kuai; Yin Yue-Wei; Li Xiao-Guang

2013-01-01

We review colossal magnetoresistance in single phase manganites, as related to the field sensitive spin-charge interactions and phase separation; the rectifying property and negative/positive magnetoresistance in manganite/Nb:SrTiO 3 p—n junctions in relation to the special interface electronic structure; magnetoelectric coupling in manganite/ferroelectric structures that takes advantage of strain, carrier density, and magnetic field sensitivity; tunneling magnetoresistance in tunnel junctions with dielectric, ferroelectric, and organic semiconductor spacers using the fully spin polarized nature of manganites; and the effect of particle size on magnetic properties in manganite nanoparticles. (topical review - magnetism, magnetic materials, and interdisciplinary research)

Large magnetoresistance in La-Ca-Mn-O films

International Nuclear Information System (INIS)

Chen, L.H.; Jin, S.; Tiefel, T.H.; Ramesh, R.; Schurig, D.

1995-01-01

A very large magnetoresistance value in excess of 10 6 % has been obtained at 110 K, H = 6 T in La-Ca-Mn-O thin films epitaxially grown on LaAlO 3 substrates by pulsed laser deposition. The as-deposited film exhibits a substantial magnetoresistance value of 39,000%, which is further improved by heat treatment. A strong dependence of the magnetoresistance on film thickness was observed, with the value reduced by orders of magnitude when the film is made thicker than ∼2,000 angstrom. This behavior is interpreted in terms of lattice strain in the La-Ca-Mn-O films

Creeping of hysteresis cycles; Reptation des cycles d'hysteresis

Energy Technology Data Exchange (ETDEWEB)

Neel, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Faculte des Sciences de Grenoble, 38 (France)

1959-07-01

Creeping consists of a kind of progressive translation of dissymmetric ferromagnetic hysteresis cycles as a function of the order number of the cycle. It is interpreted here by means of a probable coupling field, the existence of which is connected to a statistical conception of the distribution of the elementary regions. (author) [French] La reptation consiste en une sorte de translation progressive des cycles d'hysteresis ferromagnetiques dissymetriques en fonction du numero d'ordre du cycle. L'auteur l'interprete au moyen d'un champ aleatoire de couplage dont l'existence est liee a une conception statistique de la distribution des domaines elementaires. (auteur)

Model-Based, Closed-Loop Control of PZT Creep for Cavity Ring-Down Spectroscopy.

Science.gov (United States)

McCartt, A D; Ognibene, T J; Bench, G; Turteltaub, K W

2014-09-01

Cavity ring-down spectrometers typically employ a PZT stack to modulate the cavity transmission spectrum. While PZTs ease instrument complexity and aid measurement sensitivity, PZT hysteresis hinders the implementation of cavity-length-stabilized, data-acquisition routines. Once the cavity length is stabilized, the cavity's free spectral range imparts extreme linearity and precision to the measured spectrum's wavelength axis. Methods such as frequency-stabilized cavity ring-down spectroscopy have successfully mitigated PZT hysteresis, but their complexity limits commercial applications. Described herein is a single-laser, model-based, closed-loop method for cavity length control.

Role of spin polarized tunneling in magnetoresistance and low

Indian Academy of Sciences (India)

Role of spin polarized tunneling in magnetoresistance and low temperature minimum of polycrystalline La1–KMnO3 ( = 0.05, 0.1, ... Manganites; magnetoresistance; low temperature resistivity; spin polarized tunneling. ... Current Issue

Anisotropic magnetoresistance and thermodynamic fluctuations in high-temperature superconductors

International Nuclear Information System (INIS)

Heine, G.

1999-05-01

Measurements of the in-plane and out-of-plane resistivity and the transverse and longitudinal in-plane and out-of-plane magnetoresistance above T, are reported in the high-temperature superconductors Bi2Sr2CaCu208+' and YBa2CU307 b . The carrier concentration of the Bi2Sr2CaCu208+' single crystals covers a broad range of the phase diagram from the slightly under doped to the moderately over doped region. The doping concentration of the thin films ranges from strongly under doped to optimally doped. The in-plane resistivities obey a metallic-like temperature dependence with a positive magnetoresistance in the transverse and the longitudinal orientation of the magnetic field. The out-of-plane resistivities show an activated behavior above T, with a metallic region at higher temperatures and negative magnetoresistance. The data were analyzed in the framework of a model for superconducting order parameter fluctuations. The positive in-plane magnetoresistance of the highly anisotropic Bi2Sr2CaCu208+x single crystals is interpreted as the suppression of the fluctuation-conductivity enhancement including orbital and spin contributions, whereas the negative magnetoresistance arises from the reduction of the fluctuation-induced pseudogap in the single-electron density-of-states by the magnetic field. For higher temperatures a transition to the normal-state magnetoresistance occurs for the in-plane transport. In the less anisotropic YBa2CU307 b thin films the positive out-of-plane magnetoresistance near T, changes sign to a negative magnetoresistance at higher temperatures. This behavior is also consistent with predictions from the theory of thermodynamic order-parameter fluctuations. The agreement of the fluctuation theory with the experimental findings is excellent for samples from the over doped side of the phase diagram, but deteriorate with decreasing carrier concentration. This behavior is interpreted by the dominating d-wave symmetry of the superconducting order

Magnetoresistance and magnetic ordering in praseodymium and neodymium hexaborides

International Nuclear Information System (INIS)

Anisimov, M. A.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Samarin, N. A.; Filipov, V. B.; Shitsevalova, N. Yu.; Kuznetsov, A. V.; Sluchanko, N. E.

2009-01-01

The magnetoresistance Δρ/ρ of single-crystal samples of praseodymium and neodymium hexaborides (PrB 6 and NdB 6 ) has been measured at temperatures ranging from 2 to 20 K in a magnetic field of up to 80 kOe. The results obtained have revealed a crossover of the regime from a small negative magnetoresistance in the paramagnetic state to a large positive magnetoresistive effect in magnetically ordered phases of the PrB 6 and NdB 6 compounds. An analysis of the dependences Δρ(H)/ρ has made it possible to separate three contributions to the magnetoresistance for the compounds under investigation. In addition to the main negative contribution, which is quadratic in the magnetic field (-Δρ/ρ ∝ H 2 ), a linear positive contribution (Δρ/ρ ∝ H) and a nonlinear ferromagnetic contribution have been found. Upon transition to a magnetically ordered state, the linear positive component in the magnetoresistance of the PrB 6 and NdB 6 compounds becomes dominant, whereas the quadratic contribution to the negative magnetoresistance is completely suppressed in the commensurate magnetic phase of these compounds. The presence of several components in the magnetoresistance has been explained by assuming that, in the antiferromagnetic phases of PrB 6 and NdB 6 , ferromagnetic nanoregions (ferrons) are formed in the 5d band in the vicinity of the rareearth ions. The origin of the quadratic contribution to the negative magnetoresistance is interpreted in terms of the Yosida model, which takes into account scattering of conduction electrons by localized magnetic moments of rare-earth ions. Within the approach used, the local magnetic susceptibility χ loc has been estimated. It has been demonstrated that, in the temperature range T N loc for the compounds under investigation can be described with good accuracy by the Curie-Weiss dependence χ loc ∝ (T - Θ p ) -1 .

Probing giant magnetoresistance with THz spectroscopy

DEFF Research Database (Denmark)

Jin, Zuanming; Tkach, Alexander; Casper, Frederick

2014-01-01

We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA.......We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA....

3000% high-field magnetoresistance in super-lattices of CoFe nanoparticles

International Nuclear Information System (INIS)

Tan, Reasmey P.; Carrey, Julian; Respaud, Marc; Desvaux, Celine; Renaud, Philippe; Chaudret, Bruno

2008-01-01

We report on magnetotransport measurements on millimeter-large super-lattices of CoFe nanoparticles surrounded by an organic layer. Electrical properties are typical of Coulomb blockade in three-dimensional arrays of nanoparticles. A large high-field magnetoresistance, reaching up to 3000%, is measured between 1.8 and 10 K. This exceeds by two orders of magnitude magnetoresistance values generally measured in arrays of 3d transition metal ferromagnetic nanoparticles. The magnetoresistance amplitude scales with the magnetic field/temperature ratio and displays an unusual exponential dependency with the applied voltage. The magnetoresistance abruptly disappears below 1.8 K. We propose that the magnetoresistance is due to some individual paramagnetic moments localized between the metallic cores of the nanoparticles, the origin of which is discussed

Big magnetoresistance: magnetic polarons

International Nuclear Information System (INIS)

Teresa, J.M. de; Ibarra, M.R.

1997-01-01

By using several macro and microscopic experimental techniques we have given evidence for magnetoresistance in manganese oxides caused by the effect of the magnetic field on the magnetic polarons. (Author) 3 refs

Hysteresis critical point of nitrogen in porous glass: occurrence of sample spanning transition in capillary condensation.

Science.gov (United States)

Morishige, Kunimitsu

2009-06-02

To examine the mechanisms for capillary condensation and for capillary evaporation in porous glass, we measured the hysteresis critical points and desorption scanning curves of nitrogen in four kinds of porous glasses with different pore sizes (Vycor, CPG75A, CPG120A, and CPG170A). The shapes of the hysteresis loop in the adsorption isotherm of nitrogen for the Vycor and the CPG75A changed with temperature, whereas those for the CPG120A and the CPG170A remained almost unchanged with temperature. The hysteresis critical points for the Vycor and the CPG75A fell on the common line observed previously for ordered mesoporous silicas. On the other hand, the hysteresis critical points for the CPG120A and the CPG170A deviated appreciably from the common line. This strongly suggests that capillary evaporation of nitrogen in the interconnected and disordered pores of both the Vycor and the CPG75A follows a cavitation process at least in the vicinity of their hysteresis critical temperatures in the same way as that in the cagelike pores of the ordered silicas, whereas the hysteresis critical points in the CPG120A and the CPG170A have origin different from that in the cagelike pores. The desorption scanning curves for the CPG75A indicated the nonindependence of the porous domains. On the other hand, for both the CPG120A and the CPG170A, we obtained the scanning curves that are expected from the independent domain theory. All these results suggest that sample spanning transitions in capillary condensation and evaporation take place inside the interconnected pores of both the CPG120A and the CPG170A.

Magnetoresistive properties of non-uniform state of antiferromagnetic semiconductors

International Nuclear Information System (INIS)

Krivoruchko, V.N.

1996-01-01

The phenomenological model of magnetoresistive properties of magneto-non-single-phase state of alloyed magnetic semiconductors is considered using the concept derived for a description of magnetoresistive effects in layered and granular magnetic metals. By assuming that there exists a magneto-non-single state in the manganites having the perovskite structure, it is possible to describe, in the framework of above approach, large magnetoresistive effects of manganite phases with antiferromagnetic order and semiconductor-type conductivity as well as those with antiferromagnetic properties and metallic-type conductivity

A neural approach for the numerical modeling of two-dimensional magnetic hysteresis

International Nuclear Information System (INIS)

Cardelli, E.; Faba, A.; Laudani, A.; Riganti Fulginei, F.; Salvini, A.

2015-01-01

This paper deals with a neural network approach to model magnetic hysteresis at macro-magnetic scale. Such approach to the problem seems promising in order to couple the numerical treatment of magnetic hysteresis to FEM numerical solvers of the Maxwell's equations in time domain, as in case of the non-linear dynamic analysis of electrical machines, and other similar devices, making possible a full computer simulation in a reasonable time. The neural system proposed consists of four inputs representing the magnetic field and the magnetic inductions components at each time step and it is trained by 2-d measurements performed on the magnetic material to be modeled. The magnetic induction B is assumed as entry point and the output of the neural system returns the predicted value of the field H at the same time step. A suitable partitioning of the neural system, described in the paper, makes the computing process rather fast. Validations with experimental tests and simulations for non-symmetric and minor loops are presented

Improving Atomic Force Microscopy Imaging by a Direct Inverse Asymmetric PI Hysteresis Model

Directory of Open Access Journals (Sweden)

Dong Wang

2015-02-01

Full Text Available A modified Prandtl–Ishlinskii (PI model, referred to as a direct inverse asymmetric PI (DIAPI model in this paper, was implemented to reduce the displacement error between a predicted model and the actual trajectory of a piezoelectric actuator which is commonly found in AFM systems. Due to the nonlinearity of the piezoelectric actuator, the standard symmetric PI model cannot precisely describe the asymmetric motion of the actuator. In order to improve the accuracy of AFM scans, two series of slope parameters were introduced in the PI model to describe both the voltage-increase-loop (trace and voltage-decrease-loop (retrace. A feedforward controller based on the DIAPI model was implemented to compensate hysteresis. Performance of the DIAPI model and the feedforward controller were validated by scanning micro-lenses and standard silicon grating using a custom-built AFM.

Electrically tuned magnetic order and magnetoresistance in a topological insulator.

Science.gov (United States)

Zhang, Zuocheng; Feng, Xiao; Guo, Minghua; Li, Kang; Zhang, Jinsong; Ou, Yunbo; Feng, Yang; Wang, Lili; Chen, Xi; He, Ke; Ma, Xucun; Xue, Qikun; Wang, Yayu

2014-09-15

The interplay between topological protection and broken time reversal symmetry in topological insulators may lead to highly unconventional magnetoresistance behaviour that can find unique applications in magnetic sensing and data storage. However, the magnetoresistance of topological insulators with spontaneously broken time reversal symmetry is still poorly understood. In this work, we investigate the transport properties of a ferromagnetic topological insulator thin film fabricated into a field effect transistor device. We observe a complex evolution of gate-tuned magnetoresistance, which is positive when the Fermi level lies close to the Dirac point but becomes negative at higher energies. This trend is opposite to that expected from the Berry phase picture, but is intimately correlated with the gate-tuned magnetic order. The underlying physics is the competition between the topology-induced weak antilocalization and magnetism-induced negative magnetoresistance. The simultaneous electrical control of magnetic order and magnetoresistance facilitates future topological insulator based spintronic devices.

Memory characteristics of hysteresis and creep in multi-layer piezoelectric actuators: An experimental analysis

Energy Technology Data Exchange (ETDEWEB)

Biggio, Matteo [Department of Electrical, Electronic, Telecommunications Engineering and Naval Architecture, University of Genoa, Via Opera Pia 11a, Genova (Italy); Butcher, Mark [Engineering Department, CERN (Switzerland); Giustiniani, Alessandro; Masi, Alessandro [Engineering Department, CERN (Switzerland); Department of Engineering, University of Sannio, Piazza Roma, 21, I-82100 Benevento (Italy); Storace, Marco, E-mail: marco.storace@unige.it [Department of Electrical, Electronic, Telecommunications Engineering and Naval Architecture, University of Genoa, Via Opera Pia 11a, Genova (Italy)

2014-02-15

In this paper we provide an experimental characterization of creep and hysteresis in a multi-layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first-order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.

Memory characteristics of hysteresis and creep in multi-layer piezoelectric actuators: An experimental analysis

CERN Document Server

Biggio, Matteo; Giustiniani, Alessandro; Masi, Alessandro; Storace, Marco

2014-01-01

In this paper we provide an experimental characterization of creep and hysteresis in a multi layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.

Magnetoresistive waves in plasmas

International Nuclear Information System (INIS)

Felber, F.S.; Hunter, R.O. Jr.; Pereira, N.R.; Tajima, T.

1982-01-01

The self-generated magnetic field of a current diffusing into a plasma between conductors can magnetically insulate the plasma. Propagation of magnetoresistive waves in plasmas is analyzed. Applications to plasma opening switches are discussed

Fusion neutron effects on magnetoresistivity of copper stabilizer materials

International Nuclear Information System (INIS)

Guinan, M.W.; Van Konynenburg, R.A.

1983-01-01

Eight copper wires were repeatedly irradiated at 4.2 to 4.4 K with 14.8 MV neutrons and isochronally annealed at temperatures up to 34 0 C for a total of five cycles. Their electrical resistances were monitored during irradiation under zero applied magnetic field. After each irradiation the magnetoresistances were measured in applied transverse magnetic fields of up to 12 T. Then the samples were isochronally annealed to observe the recovery of the resistivity and magnetoresistivity. After each anneal at the highest temperature (34 0 C), some of the damage remained and contributed to the damage state observed following the subsequent irradiation. In this way, we were able to observe how the changes in magnetoresistance would accumulate during the repeated irradiations and anneals expected to be characteristic of fusion reactor magnets. For each succeeding irradiation the fluence was chosen to produce approximately the same final magnetoresistance at 12 T, taking account of the accumulating residual radiation damage. The increment of magnetoresistivity added by the irradiation varied from 35 to 65% at 12 T and from 50 to 90% at 8 T for the various samples

Hysteresis development in superconducting Josephson junctions

International Nuclear Information System (INIS)

Refai, T.F.; Shehata, L.N.

1988-09-01

The resistively and capacitive shunted junction model is used to investigate hysteresis development in superconducting Josephson junctions. Two empirical formulas that relate the hysteresis width and the quasi-particle diffusion length in terms of the junctions electrical parameters, temperature and frequency are obtained. The obtained formulas provide a simple tool to investigate the full potentials of the hysteresis phenomena. (author). 9 refs, 3 figs

Fatigue Load Modeling and Control for Wind Turbines based on Hysteresis Operators

DEFF Research Database (Denmark)

Barradas Berglind, Jose de Jesus; Wisniewski, Rafal; Soltani, Mohsen

2015-01-01

method based on hysteresis operators, which can be used in control loops. Furthermore, we propose a model predictive control (MPC) strategy that incorporates the online fatigue estimation through the objective function, where the ultimate goal in mind is to reduce the fatigue load of the wind turbine......The focus of this work is on fatigue load modeling and controller design for the wind turbine level. The main purpose is to include a model of the damage effects caused by the fatigue of the wind turbine components in the controller design process. This paper addresses an online fatigue estimation...

Texture development and strain hysteresis in a NiTi shape-memory alloy during thermal cycling under load

International Nuclear Information System (INIS)

Ye, B.; Majumdar, B.S.; Dutta, I.

2009-01-01

Thermal cycling experiments were conducted on a NiTi shape-memory alloy at different constant applied stresses below the yield strength of the martensite. The mechanical strain response manifested as strain hysteresis loops, whose range was proportional to the applied stress. In situ neutron diffraction experiments show that the strain hysteresis occurs as a result of the establishment of a stress-dependent crystallographic texture of the martensite during the first cool-down from austenite, and thereafter repeated during thermal cycling under the same load. This texture is found to depend on the stress during the thermal cycling experiments. A strain-pole map is derived and shown to explain the observed texture during thermal cycling. The strain-pole methodology is shown to work with similar martensitic transformations in other material systems.

Transport hysteresis and hydrogen isotope effect on confinement

Science.gov (United States)

Itoh, S.-I.; Itoh, K.

2018-03-01

A Gedankenexperiment on hydrogen isotope effect is developed, using the transport model with transport hysteresis. The transport model with hysteresis is applied to case where the modulational electron cyclotron heating is imposed near the mid-radius of the toroidal plasmas. The perturbation propagates either outward or inward, being associated with the clockwise (CW) hysteresis or counter-clockwise (CCW) hysteresis, respectively. The hydrogen isotope effects on the CW and CCW hysteresis are investigated. The local component of turbulence-driven transport is assumed to be the gyro-Bohm diffusion. While the effect of hydrogen mass number is screened in the response of CW hysteresis, it is amplified in CCW hysteresis. This result motivates the experimental studies to compare CW and CCW cases in order to obtain further insight into the physics of hydrogen isotope effects.

Experimental comparison of rate-dependent hysteresis models in characterizing and compensating hysteresis of piezoelectric tube actuators

Energy Technology Data Exchange (ETDEWEB)

Aljanaideh, Omar, E-mail: omaryanni@gmail.com [Department of Mechanical Engineering, The University of Jordan, Amman 11942 (Jordan); Habineza, Didace; Rakotondrabe, Micky [AS2M department, FEMTO-ST Institute, Univ. Bourgogne Franche-Comté, Univ. de Franche-Comté/CNRS/ENSMM, 25000 Besançon (France); Al Janaideh, Mohammad [Department of Mechanical and Industrial Engineering, The Mechatronics and Microsystems Design Laboratory, University of Toronto (Canada); Department of Mechatronics Engineering, The University of Jordan, Amman 11942 (Jordan)

2016-04-01

An experimental study has been carried out to characterize rate-dependent hysteresis of a piezoelectric tube actuator at different excitation frequencies. The experimental measurements were followed by modeling and compensation of the hysteresis nonlinearities of the piezoelectric tube actuator using both the inverse rate-dependent Prandtl–Ishlinskii model (RDPI) and inverse rate-independent Prandtl–Ishlinskii model (RIPI) coupled with a controller. The comparison of hysteresis modeling and compensation of the actuator with both models is presented.

Experimental comparison of rate-dependent hysteresis models in characterizing and compensating hysteresis of piezoelectric tube actuators

International Nuclear Information System (INIS)

Aljanaideh, Omar; Habineza, Didace; Rakotondrabe, Micky; Al Janaideh, Mohammad

2016-01-01

An experimental study has been carried out to characterize rate-dependent hysteresis of a piezoelectric tube actuator at different excitation frequencies. The experimental measurements were followed by modeling and compensation of the hysteresis nonlinearities of the piezoelectric tube actuator using both the inverse rate-dependent Prandtl–Ishlinskii model (RDPI) and inverse rate-independent Prandtl–Ishlinskii model (RIPI) coupled with a controller. The comparison of hysteresis modeling and compensation of the actuator with both models is presented.

Experimental investigation of the nature of the magnetoresistance effects in Pd-YIG hybrid structures.

Science.gov (United States)

Lin, Tao; Tang, Chi; Alyahayaei, Hamad M; Shi, Jing

2014-07-18

In bilayers consisting of Pd and yttrium iron garnet (Y(3)Fe(5)O(12) or YIG), we observe vanishingly small room-temperature conventional anisotropic magnetoresistance but large new magnetoresistance that is similar to the spin Hall magnetoresistance previously reported in Pt-YIG bilayers. We report a temperature dependence study of the two magnetoresistance effects in Pt-YIG bilayers. As the temperature is decreased, the new magnetoresistance shows a peak, whereas the anisotropic magnetoresistance effect starts to appear and increases monotonically. We find that the magnetoresistance peak shifts to lower temperatures in thicker Pd samples, a feature characteristic of the spin current effect. The distinct temperature dependence reveals fundamentally different mechanisms responsible for the two effects in such hybrid structures.

Ballistic Anisotropic Magnetoresistance of Single-Atom Contacts.

Science.gov (United States)

Schöneberg, J; Otte, F; Néel, N; Weismann, A; Mokrousov, Y; Kröger, J; Berndt, R; Heinze, S

2016-02-10

Anisotropic magnetoresistance, that is, the sensitivity of the electrical resistance of magnetic materials on the magnetization direction, is expected to be strongly enhanced in ballistic transport through nanoscale junctions. However, unambiguous experimental evidence of this effect is difficult to achieve. We utilize single-atom junctions to measure this ballistic anisotropic magnetoresistance (AMR). Single Co and Ir atoms are deposited on domains and domain walls of ferromagnetic Fe layers on W(110) to control their magnetization directions. They are contacted with nonmagnetic tips in a low-temperature scanning tunneling microscope to measure the junction conductances. Large changes of the magnetoresistance occur from the tunneling to the ballistic regime due to the competition of localized and delocalized d-orbitals, which are differently affected by spin-orbit coupling. This work shows that engineering the AMR at the single atom level is feasible.

Factors influencing hysteresis characteristics of concrete dam deformation

Directory of Open Access Journals (Sweden)

Jia-he Zhang

2017-04-01

Full Text Available Thermal deformation of a concrete dam changes periodically, and its variation lags behind the air temperature variation. The lag, known as the hysteresis time, is generally attributed to the low velocity of heat conduction in concrete, but this explanation is not entirely sufficient. In this paper, analytical solutions of displacement hysteresis time for a cantilever beam and an arch ring are derived. The influence of different factors on the displacement hysteresis time was examined. A finite element model was used to verify the reliability of the theoretical analytical solutions. The following conclusions are reached: (1 the hysteresis time of the mean temperature is longer than that of the linearly distributed temperature difference; (2 the dam type has a large impact on the displacement hysteresis time, and the hysteresis time of the horizontal displacement of an arch dam is longer than that of a gravity dam; (3 the reservoir water temperature variation lags behind of the air temperature variation, which intensifies the differences in the horizontal displacement hysteresis time between the gravity dam and the arch dam; (4 with a decrease in elevation, the horizontal displacement hysteresis time of a gravity dam tends to increase, whereas the horizontal displacement hysteresis time of an arch dam is likely to increase initially, and then decrease; and (5 along the width of the dam, the horizontal displacement hysteresis time of a gravity dam decreases as a whole, while the horizontal displacement hysteresis time of an arch dam is shorter near the center and longer near dam surfaces.

Optically Tunable Magnetoresistance Effect: From Mechanism to Novel Device Application.

Science.gov (United States)

Liu, Pan; Lin, Xiaoyang; Xu, Yong; Zhang, Boyu; Si, Zhizhong; Cao, Kaihua; Wei, Jiaqi; Zhao, Weisheng

2017-12-28

The magnetoresistance effect in sandwiched structure describes the appreciable magnetoresistance effect of a device with a stacking of two ferromagnetic layers separated by a non-magnetic layer (i.e., a sandwiched structure). The development of this effect has led to the revolution of memory applications during the past decades. In this review, we revisited the magnetoresistance effect and the interlayer exchange coupling (IEC) effect in magnetic sandwiched structures with a spacer layer of non-magnetic metal, semiconductor or organic thin film. We then discussed the optical modulation of this effect via different methods. Finally, we discuss various applications of these effects and present a perspective to realize ultralow-power, high-speed data writing and inter-chip connection based on this tunable magnetoresistance effect.

Effect of crystallinity on the magnetoresistance in perovskite manganese oxide thin films

International Nuclear Information System (INIS)

Shreekala, R.; Rajeswari, M.; Ghosh, K.; Goyal, A.; Gu, J.Y.; Kwon, C.; Trajanovic, Z.; Boettcher, T.; Greene, R.L.; Ramesh, R.; Venkatesan, T.

1997-01-01

We report our study of the effect of crystallinity on the magnetoresistance in epitaxial and polycrystalline La 2/3 Ba 1/3 MnO 3 and La 2/3 Ca 1/3 MnO 3 thin films. Magnetoresistance in epitaxial films exhibits field dependence and temperature dependence similar to bulk single crystals and sintered bulk ceramics. The polycrystalline films exhibit a markedly different behavior. The magnetoresistance in this case shows either a monotonic increase or saturation with decreasing temperature in contrast to that of epitaxial films in which the magnetoresistance peaks close to the ferromagnetic transition temperature. The field dependence in the polycrystalline films is also remarkably different. At low fields, we observe a sharp drop in resistance followed by a more gradual decrease at higher fields. Our data suggest that in addition to the intrinsic magnetoresistance, grain-boundary transport contributes significantly to the magnetoresistance in polycrystalline films. copyright 1997 American Institute of Physics

Magnetoresistance at artificial interfaces in epitaxial ferromagnetic thin films

International Nuclear Information System (INIS)

Fontcuberta, J.; Bibes, M.; Martinez, B.; Trtik, V.; Ferrater, C.; Sanchez, F.; Varela, M.

2000-01-01

Epitaxial La 2/3 Sr 1/3 MnO 3 and SrRuO 3 thin films have been grown by laser ablation on single-crystalline SrTiO 3 substrates. Prior to manganite or ruthenate deposition tracks have been patterned on the SrTiO 3 substrate by using an appropriately focused laser beam. In the experiments here reported linear tracks have been formed. The magnetotransport properties of the films, particularly the magnetoresistance, along paths parallel and perpendicular to the track have been extensively investigated and compared to similar data recorded on films grown on bicrystalline STO substrates. Whereas in LSMO a significant low-field tunnel magnetoresistance develops across the artificial interface, in SRO this tunnel contribution is absent. However, a significant high-field magnetoresistance is observed for both metallic and ferromagnetic systems. The results are analysed and discussed within the framework of the current understanding of double exchange and itinerant ferromagnets. Magnetoresistance data for various configurations of the track array are presented

Linear negative magnetoresistance in two-dimensional Lorentz gases

Science.gov (United States)

Schluck, J.; Hund, M.; Heckenthaler, T.; Heinzel, T.; Siboni, N. H.; Horbach, J.; Pierz, K.; Schumacher, H. W.; Kazazis, D.; Gennser, U.; Mailly, D.

2018-03-01

Two-dimensional Lorentz gases formed by obstacles in the shape of circles, squares, and retroreflectors are reported to show a pronounced linear negative magnetoresistance at small magnetic fields. For circular obstacles at low number densities, our results agree with the predictions of a model based on classical retroreflection. In extension to the existing theoretical models, we find that the normalized magnetoresistance slope depends on the obstacle shape and increases as the number density of the obstacles is increased. The peaks are furthermore suppressed by in-plane magnetic fields as well as by elevated temperatures. These results suggest that classical retroreflection can form a significant contribution to the magnetoresistivity of two-dimensional Lorentz gases, while contributions from weak localization cannot be excluded, in particular for large obstacle densities.

Magnetoresistance effect in (La, Sr)MnO3 bicrystalline films.

Science.gov (United States)

Alejandro, G; Steren, L B; Pastoriza, H; Vega, D; Granada, M; Sánchez, J C Rojas; Sirena, M; Alascio, B

2010-09-01

The angular dependence of the magnetoresistance effect has been measured on bicrystalline La(0.75)Sr(0.25)MnO(3) films. The measurements have been performed on an electronically lithographed Wheatstone bridge. The study of the angular dependence of both the magnetoresistance and the resistance of single-crystalline and grain-boundary regions of the samples allowed us to isolate two contributions of low-field magnetoresistance in manganites. One of them is associated with the spin-orbit effect, i.e. the anisotropic magnetoresistance of ferromagnetic compounds, and the other one is related to spin-disorder regions at the grain boundary. Complementary x-ray diffraction, ferromagnetic resonance and low temperature magnetization experiments contribute to the characterization of the magnetic anisotropy of the samples and the general comprehension of the problem.

Magnetoresistance effect in (La, Sr)MnO3 bicrystalline films

International Nuclear Information System (INIS)

Alejandro, G; Pastoriza, H; Granada, M; Rojas Sanchez, J C; Sirena, M; Alascio, B; Steren, L B; Vega, D

2010-01-01

The angular dependence of the magnetoresistance effect has been measured on bicrystalline La 0.75 Sr 0.25 MnO 3 films. The measurements have been performed on an electronically lithographed Wheatstone bridge. The study of the angular dependence of both the magnetoresistance and the resistance of single-crystalline and grain-boundary regions of the samples allowed us to isolate two contributions of low-field magnetoresistance in manganites. One of them is associated with the spin-orbit effect, i.e. the anisotropic magnetoresistance of ferromagnetic compounds, and the other one is related to spin-disorder regions at the grain boundary. Complementary x-ray diffraction, ferromagnetic resonance and low temperature magnetization experiments contribute to the characterization of the magnetic anisotropy of the samples and the general comprehension of the problem.

Influence of applied tensile stress on the hysteresis curve and magnetic domain structure of grain-oriented Fe–3%Si steel

Czech Academy of Sciences Publication Activity Database

Perevertov, Oleksiy; Schäfer, R.

2014-01-01

Roč. 47, č. 18 (2014), s. 1-10 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP107/11/0391 Grant - others:AVČR(CZ) M100100906 Institutional support: RVO:68378271 Keywords : magnetic domains * magnetization process * magnetoelasticity * hysteresis loops * tension * silicon steel * Kerr microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.721, year: 2014

Tunneling Negative Magnetoresistance via δ Doping in a Graphene-Based Magnetic Tunnel Junction

International Nuclear Information System (INIS)

Yuan Jian-Hui; Chen Ni; Mo Hua; Zhang Yan; Zhang Zhi-Hai

2016-01-01

We investigate the tunneling magnetoresistance via δ doping in a graphene-based magnetic tunnel junction in detail. It is found that the transmission probability and the conductance oscillates with the position and the aptitude of the δ doping. Also, both the transmission probability and the conductance at the parallel configuration are suppressed by the magnetic field more obviously than that at the antiparallel configuration, which implies a large negative magnetoresistance for this device. The results show that the negative magnetoresistance of over 300% at B = 1.0 T is observed by choosing suitable doped parameters, and the temperature plays an important role in the magnetoresistance. Thus it is possible to open a way to effectively manipulate the magnetoresistance devices, and to make a type of magnetoresistance device by controlling the structural parameter of the δ doping. (paper)

Deposition temperature influence on sputtered nanogranular magnetoresistive composites

International Nuclear Information System (INIS)

Mujika, M.; Arana, S.; Castano, E.

2007-01-01

Among different physical principles magnetic sensors for low magnetic field detection can be based on, granular giant magnetoresistances have been studied due to their high sensitivity to small field changes and gradual magnetoresistance change at low fields. Following this aim, nanogranular Ag-Co thin films, deposited by DC co-sputtering from Ag and Co targets at different deposition temperatures have been tested. Samples have been grown at room temperature, 100 and 200 deg. C and annealed in a mixture of N 2 and H 2 at 200 and 300 deg. C for 45 min. The samples that have shown the best performance have been subjected to two sets of measurements where an external field has been applied in-plane and perpendicular to the film plane. The best performance has been shown by the samples deposited at room temperature and annealed at 300 deg. C, reporting a maximum value of magnetoresistance of 16.7% at 1.4 T and a linear sensitivity of 63%/T between 0.04 and 0.07 T within a magnetoresistance range varying from 1.5% to 3% when subjected to an in-plane external field

Magnetoresistance in two-dimensional array of Ge/Si quantum dots

Science.gov (United States)

Stepina, N. P.; Koptev, E. S.; Pogosov, A. G.; Dvurechenskii, A. V.; Nikiforov, A. I.; Zhdanov, E. Yu

2012-07-01

Magnetoresistance in two-dimensional array of Ge/Si was studied for a wide range of the conductance, where the transport regime changes from hopping to diffusive one. The behavior of magnetoresistance is similar for all samples; it is negative in weak fields and becomes positive with increasing of magnetic field. Negative magnetoresistance can be described in the frame of weak localization approach with suggestion that quantum interference contribution to the conductance is restricted not only by the phase breaking length but also by the localization length.

Magnetoresistance in two-dimensional array of Ge/Si quantum dots

International Nuclear Information System (INIS)

Stepina, N P; Koptev, E S; Pogosov, A G; Dvurechenskii, A V; Nikiforov, A I; Zhdanov, E Yu

2012-01-01

Magnetoresistance in two-dimensional array of Ge/Si was studied for a wide range of the conductance, where the transport regime changes from hopping to diffusive one. The behavior of magnetoresistance is similar for all samples; it is negative in weak fields and becomes positive with increasing of magnetic field. Negative magnetoresistance can be described in the frame of weak localization approach with suggestion that quantum interference contribution to the conductance is restricted not only by the phase breaking length but also by the localization length.

Gate-tunable large magnetoresistance in an all-semiconductor spin valve device.

Science.gov (United States)

Oltscher, M; Eberle, F; Kuczmik, T; Bayer, A; Schuh, D; Bougeard, D; Ciorga, M; Weiss, D

2017-11-27

A large spin-dependent and electric field-tunable magnetoresistance of a two-dimensional electron system is a key ingredient for the realization of many novel concepts for spin-based electronic devices. The low magnetoresistance observed during the last few decades in devices with lateral semiconducting transport channels between ferromagnetic source and drain contacts has been the main obstacle for realizing spin field effect transistor proposals. Here, we show both a large two-terminal magnetoresistance in a lateral spin valve device with a two-dimensional channel, with up to 80% resistance change, and tunability of the magnetoresistance by an electric gate. The enhanced magnetoresistance is due to finite electric field effects at the contact interface, which boost spin-to-charge conversion. The gating scheme that we use is based on switching between uni- and bidirectional spin diffusion, without resorting to spin-orbit coupling. Therefore, it can also be employed in materials with low spin-orbit coupling.

Domain configurations and hysteresis behaviors of ultrathin cobalt film deposited on copper surface

International Nuclear Information System (INIS)

Chan, Y.-L.; Jih, N.-Y.; Peng, C.-W.; Chuang, C.-H.; Lee, T.H.; Huang, J.C.A.; Hsu, Y.J.; Wei, D.H.

2007-01-01

Depositing additional Cu layer on top of a Co thin film changes the magnetic properties of buried layer significantly. Employing in situ magneto-optical Kerr effect (MOKE) to assess the magnetization behavior of uncovered and covered Co layer grown on Cu (0 0 1), the hysteresis loops give averaged, macroscopic response of the layered system. The microscopic information was examined through element-specific domain images acquired by the X-ray photoemission electron microscope (PEEM). Based on the image analysis, evidence of magnetization switching in some regions of the as-deposited Co layer upon capping 1 ML of Cu was found

Hanle Magnetoresistance in Thin Metal Films with Strong Spin-Orbit Coupling.

Science.gov (United States)

Vélez, Saül; Golovach, Vitaly N; Bedoya-Pinto, Amilcar; Isasa, Miren; Sagasta, Edurne; Abadia, Mikel; Rogero, Celia; Hueso, Luis E; Bergeret, F Sebastian; Casanova, Fèlix

2016-01-08

We report measurements of a new type of magnetoresistance in Pt and Ta thin films. The spin accumulation created at the surfaces of the film by the spin Hall effect decreases in a magnetic field because of the Hanle effect, resulting in an increase of the electrical resistance as predicted by Dyakonov [Phys. Rev. Lett. 99, 126601 (2007)]. The angular dependence of this magnetoresistance resembles the recently discovered spin Hall magnetoresistance in Pt/Y(3)Fe(5)O(12) bilayers, although the presence of a ferromagnetic insulator is not required. We show that this Hanle magnetoresistance is an alternative simple way to quantitatively study the coupling between charge and spin currents in metals with strong spin-orbit coupling.

Quantum and classical contributions to linear magnetoresistance in topological insulator thin films

International Nuclear Information System (INIS)

Singh, Sourabh; Gopal, R. K.; Sarkar, Jit; Mitra, Chiranjib

2016-01-01

Three dimensional topological insulators possess backscattering immune relativistic Dirac fermions on their surface due to nontrivial topology of the bulk band structure. Both metallic and bulk insulating topological insulators exhibit weak-antilocalization in the low magnetic field and linear like magnetoresistance in higher fields. We explore the linear magnetoresistance in bulk insulating topological insulator Bi 2-x Sb x Te 3-y Se y thin films grown by pulsed laser deposition technique. Thin films of Bi 2-x Sb x Te 3-y Se y were found to be insulating in nature, which conclusively establishes the origin of linear magnetoresistance from surface Dirac states. The films were thoroughly characterized for their crystallinity and composition and then subjected to transport measurements. We present a careful analysis taking into considerations all the existing models of linear magnetoresistance. We comprehend that the competition between classical and quantum contributions to magnetoresistance results in linear magnetoresistance in high fields. We observe that the cross-over field decreases with increasing temperature and the physical argument for this behavior is explained.

Thresholds, switches and hysteresis in hydrology from the pedon to the catchment scale: a non-linear systems theory

Directory of Open Access Journals (Sweden)

2007-01-01

Full Text Available Hysteresis is a rate-independent non-linearity that is expressed through thresholds, switches, and branches. Exceedance of a threshold, or the occurrence of a turning point in the input, switches the output onto a particular output branch. Rate-independent branching on a very large set of switches with non-local memory is the central concept in the new definition of hysteresis. Hysteretic loops are a special case. A self-consistent mathematical description of hydrological systems with hysteresis demands a new non-linear systems theory of adequate generality. The goal of this paper is to establish this and to show how this may be done. Two results are presented: a conceptual model for the hysteretic soil-moisture characteristic at the pedon scale and a hysteretic linear reservoir at the catchment scale. Both are based on the Preisach model. A result of particular significance is the demonstration that the independent domain model of the soil moisture characteristic due to Childs, Poulavassilis, Mualem and others, is equivalent to the Preisach hysteresis model of non-linear systems theory, a result reminiscent of the reduction of the theory of the unit hydrograph to linear systems theory in the 1950s. A significant reduction in the number of model parameters is also achieved. The new theory implies a change in modelling paradigm.

Magnetic refrigeration capabilities of magnetocaloric Ni2Mn:75Cu:25Ga

Science.gov (United States)

Mishra, S. K.; Jenkins, C. A.; Dubenko, I.; Samanta, T.; Ali, N.; Roy, S.

2013-03-01

Doping-driven competition between energetically similar ground states leads to many exciting materials phenomena such as the emergence of high-Tc superconductivity, diluted magnetic semiconductors, and colossal magnetoresistance. Doped Ni2MnGa Heusler alloy, which is a multifunctional ferromagnetic alloy with various exotic physical properties demonstrates this notion of rich phenomenology via modified ground spin states. Adopting this generic concept, here we will present a novel doped Ni2Mn.75Cu.25Ga alloy that offers unprecedented co-existence of the magnetocaloric effect and fully controlled ferromagnetism at room temperature. Application of site engineering enables us to manipulate the ground spin state that leads to the decrease in magnetic transition temperature and also increases the delocalization of the Mn magnetism. SQUID magnetometery suggests that Cu doping enhances the saturation magnetization, coercive field and clarity of magnetic hysteresis loops. By exploiting x-ray absorption techniques and measuring element specific magnetic hysteresis loops, here we will describe the microscopic origin of enhnaced magnetocaloric properties and d-d interaction driven charge transfer effects in Ni2Mn.75Cu.25Ga This work was supported by DOE Grant No. DE-FG02-06ER46291

Field geometry dependence of magnetotransport in epitaxial La2/3Ca1/3MnO3 thin films

International Nuclear Information System (INIS)

Saldarriaga, W.; Baca, E.; Prieto, P.; Moran, O.; Grube, K.; Fuchs, D.; Schneider, R.

2006-01-01

In-plane and out-of-plane magnetoresistance measurements on epitaxial ∼200nm thin (001)-oriented films of high oxygen pressure DC-sputtering grown manganite La 2/3 Ca 1/3 MnO 3 were carried out. Single crystal (001)-SrTiO 3 substrates were used. The samples featured a Curie temperature T C ∼260K and a magnetic moment μ(T->0K)∼3μ B per Mn atom. Magnetocrystalline anisotropy with the easy axes lying on film plane was evidenced by recording the in-plane and out-of-plane magnetization loops at temperatures, below T C , in magnetic field strengths up to 5T. Evidence for anisotropic magnetotransport in these films was provided by electric measurements in a wide temperature range up to 6T magnetic field strengths applied both perpendicular and parallel to the film plane. In both applied magnetic field geometries, current and magnetic field were maintained perpendicular to each other. Neither low-field magnetoresistance nor large magnetoresistance hysteresis were observed on these samples, suggesting that the tensile strain imposed by the substrate in the first monolayers has partially been released. In addition, by rotating the sample 360 o around an axis parallel to film plane, in magnetic fields >=2T, a quadratic sinusoidal dependence of the magnetoresistance on the polar angle θ was observed. These results can be consistently interpreted using a generalized version of the theory of anisotropic magnetoresistance in transition-metal ferromagnets

Comparative analysis of the apparent saturation hysteresis approach and the domain theory of hysteresis in respect of prediction of scanning curves and air entrapment

Science.gov (United States)

Beriozkin, A.; Mualem, Y.

2018-05-01

This study theoretically analyzes the concept of apparent saturation hysteresis, combined with the Scott et al. (1983) scaling approach, as suggested by Parker and Lenhard (1987), to account for the effect of air entrapment and release on the soil water hysteresis. We found that the theory of Parker and Lenhard (1987) is comprised of some mutually canceling mathematical operations, and when cleared of the superfluous intermediate calculations, their model reduces to the original Scott et al.'s (1983) scaling method, supplemented with the requirement of closure of scanning loops. Our analysis reveals that actually there is no effect of their technique of accounting for the entrapped air on the final prediction of the effective saturation (or water content) scanning curves. Our consideration indicates that the use of the Land (1968) formula for assessing the amount of entrapped air is in disaccord with the apparent saturation concept as introduced by Parker and Lenhard (1987). In this paper, a proper routine is suggested for predicting hysteretic scanning curves of any order, given the two measured main curves, in the complete hysteretic domain and some verification tests are carried out versus measured results. Accordingly, explicit closed-form formulae for direct prediction (with no need of intermediate calculation) of scanning curves up to the third order are derived to sustain our analysis.

Observation of large low-field magnetoresistance in spinel cobaltite: A new half-metal

KAUST Repository

Li, Peng

2015-12-10

Low-field magnetoresistance is an effective and energy-saving way to use half-metallic materials in magnetic reading heads and magnetic random access memory. Common spin-polarized materials with low field magnetoresistance effect are perovskite-type manganese, cobalt, and molybdenum oxides. In this study, we report a new type of spinel cobaltite materials, self-assembled nanocrystalline NiCo2O4, which shows large low field magnetoresistance as large as –19.1% at 0.5 T and –50% at 9 T (2 K). The large low field magnetoresistance is attributed to the fast magnetization rotation of the core nanocrystals. The surface spin-glass is responsible for the observed weak saturation of magnetoresistance under high fields. Our calculation demonstrates that the half-metallicity of NiCo2O4 comes from the hopping eg electrons within the tetrahedral Co-atoms and the octahedral Ni-atoms. The discovery of large low-field magnetoresistance in simple spinel oxide NiCo2O4, a non-perovskite oxide, leads to an extended family of low-field magnetoresistance materials. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Observation of large low-field magnetoresistance in spinel cobaltite: A new half-metal

KAUST Repository

Li, Peng; Xia, Chuan; Zheng, Dongxing; Wang, Ping; Jin, Chao; Bai, Haili

2015-01-01

Low-field magnetoresistance is an effective and energy-saving way to use half-metallic materials in magnetic reading heads and magnetic random access memory. Common spin-polarized materials with low field magnetoresistance effect are perovskite-type manganese, cobalt, and molybdenum oxides. In this study, we report a new type of spinel cobaltite materials, self-assembled nanocrystalline NiCo2O4, which shows large low field magnetoresistance as large as –19.1% at 0.5 T and –50% at 9 T (2 K). The large low field magnetoresistance is attributed to the fast magnetization rotation of the core nanocrystals. The surface spin-glass is responsible for the observed weak saturation of magnetoresistance under high fields. Our calculation demonstrates that the half-metallicity of NiCo2O4 comes from the hopping eg electrons within the tetrahedral Co-atoms and the octahedral Ni-atoms. The discovery of large low-field magnetoresistance in simple spinel oxide NiCo2O4, a non-perovskite oxide, leads to an extended family of low-field magnetoresistance materials. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Method and apparatus for sub-hysteresis discrimination

Science.gov (United States)

De Geronimo, Gianluigi

2015-12-29

Embodiments of comparator circuits are disclosed. A comparator circuit may include a differential input circuit, an output circuit, a positive feedback circuit operably coupled between the differential input circuit and the output circuit, and a hysteresis control circuit operably coupled with the positive feedback circuit. The hysteresis control circuit includes a switching device and a transistor. The comparator circuit provides sub-hysteresis discrimination and high speed discrimination.

Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites.

Science.gov (United States)

Howard, John M; Tennyson, Elizabeth M; Barik, Sabyasachi; Szostak, Rodrigo; Waks, Edo; Toney, Michael F; Nogueira, Ana F; Neves, Bernardo R A; Leite, Marina S

2018-06-12

Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs x FA 1- x Pb(I y Br 1- y ) 3 perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

Stripe domains and magnetoresistance in thermally deposited nickel films

International Nuclear Information System (INIS)

Sparks, P.D.; Stern, N.P.; Snowden, D.S.; Kappus, B.A.; Checkelsky, J.G.; Harberger, S.S.; Fusello, A.M.; Eckert, J.C.

2004-01-01

We report a study of the domain structure and magnetoresistance of thermally deposited nickel films. For films thicker than 17 nm, we observe striped domains with period varying with film thickness as a power law with exponent 0.21±0.02 up to 120 nm thickness. There is a negative magnetoresistance for fields out of the plane

Stripe domains and magnetoresistance in thermally deposited nickel films

Science.gov (United States)

Sparks, P. D.; Stern, N. P.; Snowden, D. S.; Kappus, B. A.; Checkelsky, J. G.; Harberger, S. S.; Fusello, A. M.; Eckert, J. C.

2004-05-01

We report a study of the domain structure and magnetoresistance of thermally deposited nickel films. For films thicker than 17nm, we observe striped domains with period varying with film thickness as a power law with exponent 0.21+/-0.02 up to 120nm thickness. There is a negative magnetoresistance for fields out of the plane.

Stripe domains and magnetoresistance in thermally deposited nickel films

Energy Technology Data Exchange (ETDEWEB)

Sparks, P.D. E-mail: sparks@hmc.edu; Stern, N.P.; Snowden, D.S.; Kappus, B.A.; Checkelsky, J.G.; Harberger, S.S.; Fusello, A.M.; Eckert, J.C

2004-05-01

We report a study of the domain structure and magnetoresistance of thermally deposited nickel films. For films thicker than 17 nm, we observe striped domains with period varying with film thickness as a power law with exponent 0.21{+-}0.02 up to 120 nm thickness. There is a negative magnetoresistance for fields out of the plane.

Colossal Magnetoresistance in La-Y-Ca-Mn-O Films

NARCIS (Netherlands)

Chen, L.H.; Tiefel, T.H.; Jin, S.; Palstra, T.T.M.; Ramesh, R.; Kwon, C.

1996-01-01

Magnetoresistance behavior of La0.60Y0.07CaMnOx, thin films epitaxially grown on LaAlO3 has been investigated. The films exhibit colossal magnetoresistance with the MR ratio in excess of 10^8% at ~60K, H = 7T, which is the highest ever reported for thin film manganites. The partial substitution of

Measurement of contact-angle hysteresis for droplets on nanopillared surface and in the Cassie and Wenzel states: a molecular dynamics simulation study.

Science.gov (United States)

Koishi, Takahiro; Yasuoka, Kenji; Fujikawa, Shigenori; Zeng, Xiao Cheng

2011-09-27

We perform large-scale molecular dynamics simulations to measure the contact-angle hysteresis for a nanodroplet of water placed on a nanopillared surface. The water droplet can be in either the Cassie state (droplet being on top of the nanopillared surface) or the Wenzel state (droplet being in contact with the bottom of nanopillar grooves). To measure the contact-angle hysteresis in a quantitative fashion, the molecular dynamics simulation is designed such that the number of water molecules in the droplets can be systematically varied, but the number of base nanopillars that are in direct contact with the droplets is fixed. We find that the contact-angle hysteresis for the droplet in the Cassie state is weaker than that in the Wenzel state. This conclusion is consistent with the experimental observation. We also test a different definition of the contact-angle hysteresis, which can be extended to estimate hysteresis between the Cassie and Wenzel state. The idea is motivated from the appearance of the hysteresis loop typically seen in computer simulation of the first-order phase transition, which stems from the metastability of a system in different thermodynamic states. Since the initial shape of the droplet can be controlled arbitrarily in the computer simulation, the number of base nanopillars that are in contact with the droplet can be controlled as well. We show that the measured contact-angle hysteresis according to the second definition is indeed very sensitive to the initial shape of the droplet. Nevertheless, the contact-angle hystereses measured based on the conventional and new definition seem converging in the large droplet limit. © 2011 American Chemical Society

Hysteresis compensation of the Prandtl-Ishlinskii model for piezoelectric actuators using modified particle swarm optimization with chaotic map.

Science.gov (United States)

Long, Zhili; Wang, Rui; Fang, Jiwen; Dai, Xufei; Li, Zuohua

2017-07-01

Piezoelectric actuators invariably exhibit hysteresis nonlinearities that tend to become significant under the open-loop condition and could cause oscillations and errors in nanometer-positioning tasks. Chaotic map modified particle swarm optimization (MPSO) is proposed and implemented to identify the Prandtl-Ishlinskii model for piezoelectric actuators. Hysteresis compensation is attained through application of an inverse Prandtl-Ishlinskii model, in which the parameters are formulated based on the original model with chaotic map MPSO. To strengthen the diversity and improve the searching ergodicity of the swarm, an initial method of adaptive inertia weight based on a chaotic map is proposed. To compare and prove that the swarm's convergence occurs before stochastic initialization and to attain an optimal particle swarm optimization algorithm, the parameters of a proportional-integral-derivative controller are searched using self-tuning, and the simulated results are used to verify the search effectiveness of chaotic map MPSO. The results show that chaotic map MPSO is superior to its competitors for identifying the Prandtl-Ishlinskii model and that the inverse Prandtl-Ishlinskii model can provide hysteresis compensation under different conditions in a simple and effective manner.

Dependence of Fe/Cr superlattice magnetoresistance on orientation of external magnetic field

International Nuclear Information System (INIS)

Ustinov, V.V.; Romashev, L.N.; Minin, V.I.; Semerikov, A.V.; Del', A.R.

1995-01-01

The paper presents the results of investigations into giant magnetoresistance of [Fe/Cr] 30 /MgO superlattices obtained using molecular-beam epitaxy under various orientations of magnetic field relatively to the layers of superlattice and to the direction of current flow. Theory of orientation dependence of superlattice magnetoresistance enabling to describe satisfactorily behaviour of magnetoresistance at arbitrary direction of magnetic field on the ground of results of magnetoresistance measurements in magnetic field parallel and perpendicular to plane of layers, is elaborated. It is pointed out that it is possible to obtain field dependence of superlattice magnetization on the ground of measurement results. 9 refs., 6 figs

Representation of hysteresis with wipe-out memory

International Nuclear Information System (INIS)

Friedman, G.; Cha, K.

2001-01-01

A model representing scalar hysteretic systems with wipe-out memory is proposed. In this model a hysteresis operator is represented as a power series expansion containing an infinite number of terms in general. It is shown that this representation converges to any given hysteresis relation having wipe-out memory as long as the output of the given hysteresis varies sufficiently smoothly with input history. [copyright] 2001 American Institute of Physics

On the magnetoresistance of heavy fermion compounds

International Nuclear Information System (INIS)

Lee Chengchung; Chen Chung

1992-09-01

Starting from two-conduction-band Anderson lattice model, the magneto-transport properties of heavy fermion systems are studied in the slave boson mean field theory. The residual magnetoresistivity induced by different kinds of impurities is calculated, and the experimentally detected positive maximum structure in the residual magnetoresistance of heavy fermion systems is reproduced. The transition of field-dependent resistivity from nonmonotonic to monotonic behaviour with increasing temperature can be explained naturally by including the charge fluctuation effect. The influence of applied pressure is also investigated. (author). 22 refs, 5 figs

Hysteresis Bearingless Slice Motors with Homopolar Flux-biasing.

Science.gov (United States)

Noh, Minkyun; Gruber, Wolfgang; Trumper, David L

2017-10-01

We present a new concept of bearingless slice motor that levitates and rotates a ring-shaped solid rotor. The rotor is made of a semi-hard magnetic material exhibiting magnetic hysteresis, such as D2 steel. The rotor is radially biased with a homopolar permanent-magnetic flux, on which the stator can superimpose 2-pole flux to generate suspension forces. By regulating the suspension forces based on position feedback, the two radial rotor degrees of freedom are actively stabilized. The two tilting degrees of freedom and the axial translation are passively stable due to the reluctance forces from the bias flux. In addition, the stator can generate a torque by superimposing 6- pole rotating flux, which drags the rotor via hysteresis coupling. This 6-pole flux does not generate radial forces in conjunction with the homopolar flux or 2-pole flux, and therefore the suspension force generation is in principle decoupled from the driving torque generation. We have developed a prototype system as a proof of concept. The stator has twelve teeth, each of which has a single phase winding that is individually driven by a linear transconductance power amplifier. The system has four reflective-type optical sensors to differentially measure the two radial degrees of freedom of the rotor. The suspension control loop is implemented such that the phase margin is 25 degrees at the cross-over frequency of 110 Hz. The prototype system can levitate the rotor and drive it up to about 1730 rpm. The maximum driving torque is about 2.7 mNm.

Quantum conductance in electrodeposited nanocontacts and magnetoresistance measurements

DEFF Research Database (Denmark)

Elhoussine, F.; Encinas, A.; Mátéfi-Tempfli, Stefan

2003-01-01

The conductance and magnetoresistance measurements in magnetic Ni-Ni and Co-Ni nanocontacts prepared by electrodeposition within the pores of a track of track-etched polymer membrane were discussed. At room temperature, Ni-Ni constrictions were found to show broad quantization plateaus of conduct...... of conductance during their dissolution in units of e/h, as expected for ferromagnetic ballistic nanocontacts. The measurement of the positive and negative magnetoresistance in Co-Ni nanocontacts was also elaborated....

Development of a Compensation Scheme for a Measurement Voltage Transformer Using the Hysteresis Characteristics of a Core

Directory of Open Access Journals (Sweden)

Hyewon Lee

2015-04-01

Full Text Available This paper describes the design, evaluation, and implementation of a compensation scheme for a measurement voltage transformer (VT using the hysteresis characteristics of the core. The error of a VT is caused by the primary winding voltage and secondary winding voltage. The latter depends on the secondary current, whereas the former depends on the primary current, which is an aggregate of the exciting and secondary currents. The secondary current is obtained directly from the secondary voltage and is used to obtain the voltage across the secondary winding. For the primary current, the exciting current is decomposed into two components: core-loss and magnetizing currents. The magnetizing current is obtained by the flux-magnetizing current curve instead of the hysteresis loop to minimize the required loops for compensation. The core-loss current is obtained by dividing the primary induced voltage by the core-loss resistance. Finally, the estimated voltages across the primary and secondary windings are added to the measured secondary voltage for compensation. The scheme can significantly improve the accuracy of a VT. The results of the performance of compensator are shown in the experimental test. The accuracy of the measurement VT improves from 1.0C class to 0.1C class. The scheme can help to significantly reduce the required core cross section of a measurement VT in an electrical energy system.

Large linear magnetoresistance from neutral defects in Bi$_2$Se$_3$

OpenAIRE

Kumar, Devendra; Lakhani, Archana

2016-01-01

The chalcogenide Bi$_2$Se$_3$ can attain the three dimensional (3D) Dirac semimetal state under the influence of strain and microstrain. Here we report the presnece of large linear magnetoresistance in such a Bi$_2$Se$_3$ crystal. The magnetoresistance has quadratic form at low fields which crossovers to linear above 4 T. The temperature dependence of magnetoresistance scales with carrier mobility and the crossover field scales with inverse of mobility. Our analysis suggest that the linear ma...

Large linear magnetoresistance in topological crystalline insulator Pb_0_._6Sn_0_._4Te

International Nuclear Information System (INIS)

Roychowdhury, Subhajit; Ghara, Somnath; Guin, Satya N.; Sundaresan, A.; Biswas, Kanishka

2016-01-01

Classical magnetoresistance generally follows the quadratic dependence of the magnetic field at lower field and finally saturates when field is larger. Here, we report the large positive non-saturating linear magnetoresistance in topological crystalline insulator, Pb_0_._6Sn_0_._4Te, at different temperatures between 3 K and 300 K in magnetic field up to 9 T. Magnetoresistance value as high as ∼200% was achieved at 3 K at magnetic field of 9 T. Linear magnetoresistance observed in Pb_0_._6Sn_0_._4Te is mainly governed by the spatial fluctuation carrier mobility due to distortions in the current paths in inhomogeneous conductor. - Graphical abstract: Large non-saturating linear magnetoresistance has been evidenced in topological crystalline insulator, Pb_0_._6Sn_0_._4Te, at different temperatures between 3 K and 300 K in magnetic field up to 9 T. - Highlights: • Large non-saturating linear magnetoresistance was achieved in the topological crystalline insulator, Pb_0_._6Sn_0_._4Te. • Highest magnetoresistance value as high as ~200% was achieved at 3 K at magnetic field of 9 T. • Linear magnetoresistance in Pb_0_._6Sn_0_._4Te is mainly governed by the spatial fluctuation of the carrier mobility.

Hysteresis phenomena in hydraulic measurement

International Nuclear Information System (INIS)

Ran, H J; Farhat, M; Luo, X W; Chen, Y L; Xu, H Y

2012-01-01

Hysteresis phenomena demonstrate the lag between the generation and the removal of some physical phenomena. This paper studies the hysteresis phenomena of the head-drop in a scaled model pump turbine using experiment test and CFD methods. These lag is induced by complicated flow patterns, which influenced the reliability of rotating machine. Keeping the same measurement procedure is concluded for the hydraulic machine measurement.

Magnetic anisotropy and magnetoresistance in Co-based multilayers: a polarised neutron reflectivity study

International Nuclear Information System (INIS)

Yusuf, S.M.

2000-01-01

We have studied giant magnetoresistance (GMR) and anisotropic magnetoresistance (AMR) effects by carrying out magnetization, magnetoresistance and polarized neutron reflectivity measurements on epitaxial Co/Re multilayers. Polarized neutron reflectivity study with polarization analysis gives a direct way to sense the direction of sublattice magnetization and coupling between magnetic layers. The evolution of magnetic structure as a function of the strength and direction of the applied magnetic field has been studied. The AMR effect observed in magnetoresistance study has been explained in the light of observed magnetic structure. (author)

Study of spin crossover nanoparticles thermal hysteresis using FORC diagrams on an Ising-like model

International Nuclear Information System (INIS)

Atitoaie, Alexandru; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian

2014-01-01

Recent developments in the synthesis and characterization of spin crossover (SCO) nanoparticles and their prospects of switching at molecular level turned these bistable compounds into possible candidates for replacing the materials used in recording media industry for development of solid state pressure and temperature sensors or for bringing contributions in engineering. Compared to bulk samples with the same chemical structure, SCO nanoparticles display different characteristics of the hysteretic and relaxation properties like the shift of the transition temperature towards lower values along with decrease of the hysteresis width with nanoparticles size. Using an Ising-like model with specific boundary conditions within a Monte Carlo procedure, we here reproduce most of the hysteretic properties of SCO nanoparticles by considering the interaction between spin crossover edge molecules and embedding surfactant molecules and we propose a complex analysis concerning the effect of the interactions and sizes during the thermal transition in systems of SCO nanoparticles by using the First Order Reversal Curves diagram method and by comparison with similar effects in mixed crystal systems. - Highlights: • The influence of size effects in spin crossover nanoparticles is analyzed. • The environment shifts the hysteresis loop towards lower temperatures. • First Order Reversal Curves technique is employed. • One determines the distributions of switching temperatures. • One disentangles between kinetics and non-kinetic parts of the hysteresis

Magnetoresistance effect in (La, Sr)MnO{sub 3} bicrystalline films

Energy Technology Data Exchange (ETDEWEB)

Alejandro, G; Pastoriza, H; Granada, M; Rojas Sanchez, J C; Sirena, M; Alascio, B [Centro Atomico Bariloche (CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche, Pcia. de Rio Negro (Argentina); Steren, L B; Vega, D, E-mail: galejand@cab.cnea.gov.a [Centro Atomico Constituyentes (CNEA), 1650 San MartIn, Pcia. de Buenos Aires (Argentina)

2010-09-01

The angular dependence of the magnetoresistance effect has been measured on bicrystalline La{sub 0.75}Sr{sub 0.25}MnO{sub 3} films. The measurements have been performed on an electronically lithographed Wheatstone bridge. The study of the angular dependence of both the magnetoresistance and the resistance of single-crystalline and grain-boundary regions of the samples allowed us to isolate two contributions of low-field magnetoresistance in manganites. One of them is associated with the spin-orbit effect, i.e. the anisotropic magnetoresistance of ferromagnetic compounds, and the other one is related to spin-disorder regions at the grain boundary. Complementary x-ray diffraction, ferromagnetic resonance and low temperature magnetization experiments contribute to the characterization of the magnetic anisotropy of the samples and the general comprehension of the problem.

Magnetoresistance in amorphous NdFeB/FeB compositionally modulated multilayers

International Nuclear Information System (INIS)

Peral, G.; Briones, F.; Vicent, J.L.

1991-01-01

Resistance measurements have been done in amorphous Nd 12 Fe 80 B 8 sputtered films and in amorphous sputtered Nd 26 Fe 68 B 6 /Fe 92 B 8 multilayers between 6 and 150 K with applied magnetic field parallel (LMR) and perpendicular (TMR) up to 7 T. The samples were grown by dc triode sputtering, with nominal unequal (2:1) layer thicknesses. The layered character of the samples have been tested by x-ray diffraction. Longitudinal magnetoresistance (LMR) is positive and transverse magnetoresistance (TMR) is negative. The magnetoresistance values are higher than in amorphous ferromagnets, and multilayering of these alloys produces much larger magnetoresistance values than either alloy alone and there is a strong dependence on the multilayer wavelength. The MR shows a weak temperature dependence in the temperature interval that was investigated

Unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic layer heterostructures

Science.gov (United States)

Kally, James; Lv, Yang; Zhang, Delin; Lee, Joon Sue; Samarth, Nitin; Wang, Jian-Ping; Department of Electrical; Computer Engineering, University of Minnesota, Minneapolis Collaboration; Department of Physics, Pennsylvania State University Collaboration

The surface states of topological insulators offer a potentially very efficient way to generate spins and spin-orbit torques to magnetic moments in proximity. The switching by spin-orbit torque itself only requires two terminals so that a charge current can be applied. However, a third terminal with additional magnetic tunneling junction structure is needed to sense the magnetization state if such devices are used for memory and logic applications. The recent discovery of unidirectional spin Hall magnetoresistance in heavy metal/ferromagnetic and topological insulator/magnetically doped topological insulator systems offers an alternative way to sense magnetization while still keeping the number of terminals to minimal two. The unidirectional spin Hall magnetoresistance in topological insulator/strong ferromagnetic layer heterostructure system has yet not been reported. In this work, we report our experimental observations of such magnetoresistance. It is found to be present and comparable to the best result of the previous reported Ta/Co systems in terms of magnetoresistance per current density per total resistance.

Large linear magnetoresistivity in strongly inhomogeneous planar and layered systems

International Nuclear Information System (INIS)

Bulgadaev, S.A.; Kusmartsev, F.V.

2005-01-01

Explicit expressions for magnetoresistance R of planar and layered strongly inhomogeneous two-phase systems are obtained, using exact dual transformation, connecting effective conductivities of in-plane isotropic two-phase systems with and without magnetic field. These expressions allow to describe the magnetoresistance of various inhomogeneous media at arbitrary concentrations x and magnetic fields H. All expressions show large linear magnetoresistance effect with different dependencies on the phase concentrations. The corresponding plots of the x- and H-dependencies of R(x,H) are represented for various values, respectively, of magnetic field and concentrations at some values of inhomogeneity parameter. The obtained results show a remarkable similarity with the existing experimental data on linear magnetoresistance in silver chalcogenides Ag 2+δ Se. A possible physical explanation of this similarity is proposed. It is shown that the random, stripe type, structures of inhomogeneities are the most suitable for a fabrication of magnetic sensors and a storage of information at room temperatures

Investigation of structure and magnetoresistance in Co/ZnO films

International Nuclear Information System (INIS)

Quan Zhiyong; Xu Xiaohong; Li Xiaoli; Feng, Q.; Gehring, G. A.

2010-01-01

Co/ZnO films were deposited on glass substrates by magnetron sputtering at room temperature. The structure of the as-deposited films is studied by means of x-ray diffraction, x-ray photoelectron spectroscopy, and the zero-field-cooled and field-cooled magnetization curves. It is shown that the as-deposited samples consist of a mixture of regions of metallic Co and semiconducting ZnO. Large negative magnetoresistance of 26% and 11.9% are observed in the as-deposited Co/ZnO film with Co concentration of 50.7 at. % at 10 K and room temperature, respectively. Structural analysis, the temperature dependence of the conductivity and magnetoresistance reveal that the magnetoresistance is induced by spin-dependent tunneling between regions of conducting magnetic Co through the ZnO semiconducting barriers. The enhanced magnetoresistance in the low temperature regime may be related to the existence of higher-order tunneling processes between large Co regions mediated by small Co particles.

Giant current-perpendicular-to-plane magnetoresistance in multilayer graphene as grown on nickel.

Science.gov (United States)

Bodepudi, S C; Singh, A P; Pramanik, S

2014-05-14

Strong magnetoresistance effects are often observed in ferromagnet-nonmagnet multilayers, which are exploited in state-of-the-art magnetic field sensing and data storage technologies. In this work we report a novel current-perpendicular-to-plane magnetoresistance effect in multilayer graphene as grown on a catalytic nickel surface by chemical vapor deposition. A negative magnetoresistance effect of ∼10(4)% has been observed, which persists even at room temperature. This effect is correlated with the shape of the 2D peak as well as with the occurrence of D peak in the Raman spectrum of the as-grown multilayer graphene. The observed magnetoresistance is extremely high as compared to other known materials systems for similar temperature and field range and can be qualitatively explained within the framework of "interlayer magnetoresistance" (ILMR).

Anisotropic giant magnetoresistance in NbSb2

Science.gov (United States)

Wang, Kefeng; Graf, D.; Li, Lijun; Wang, Limin; Petrovic, C.

2014-01-01

The magnetic field response of the transport properties of novel materials and then the large magnetoresistance effects are of broad importance in both science and application. We report large transverse magnetoreistance (the magnetoresistant ratio ~ 1.3 × 105% in 2 K and 9 T field, and 4.3 × 106% in 0.4 K and 32 T field, without saturation) and field-induced metal-semiconductor-like transition, in NbSb2 single crystal. Magnetoresistance is significantly suppressed but the metal-semiconductor-like transition persists when the current is along the ac-plane. The sign reversal of the Hall resistivity and Seebeck coefficient in the field, plus the electronic structure reveal the coexistence of a small number of holes with very high mobility and a large number of electrons with low mobility. The large MR is attributed to the change of the Fermi surface induced by the magnetic field which is related to the Dirac-like point, in addition to orbital MR expected for high mobility metals. PMID:25476239

Light-induced magnetoresistance in solution-processed planar hybrid devices measured under ambient conditions.

Science.gov (United States)

Banerjee, Sreetama; Bülz, Daniel; Reuter, Danny; Hiller, Karla; Zahn, Dietrich R T; Salvan, Georgeta

2017-01-01

We report light-induced negative organic magnetoresistance (OMAR) measured in ambient atmosphere in solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) planar hybrid devices with two different device architectures. Hybrid electronic devices with trench-isolated electrodes (HED-TIE) having a channel length of ca. 100 nm fabricated in this work and, for comparison, commercially available pre-structured organic field-effect transistor (OFET) substrates with a channel length of 20 µm were used. The magnitude of the photocurrent as well as the magnetoresistance was found to be higher for the HED-TIE devices because of the much smaller channel length of these devices compared to the OFETs. We attribute the observed light-induced negative magnetoresistance in TIPS-pentacene to the presence of electron-hole pairs under illumination as the magnetoresistive effect scales with the photocurrent. The magnetoresistance effect was found to diminish over time under ambient conditions compared to a freshly prepared sample. We propose that the much faster degradation of the magnetoresistance effect as compared to the photocurrent was due to the incorporation of water molecules in the TIPS-pentacene film.

Magnetoresistance and Hall resistivity of semimetal WTe2 ultrathin flakes.

Science.gov (United States)

Luo, Xin; Fang, Chi; Wan, Caihua; Cai, Jialin; Liu, Yong; Han, Xiufeng; Lu, Zhihong; Shi, Wenhua; Xiong, Rui; Zeng, Zhongming

2017-04-07

This article reports the characterization of WTe 2 thin flake magnetoresistance and Hall resistivity. We found it does not exhibit magnetoresistance saturation when subject to high fields, in a manner similar to their bulk characteristics. The linearity of Hall resistivity in our devices confirms the compensation of electrons and holes. By relating experimental results to a classic two-band model, the lower magnetoresistance values in our samples is demonstrated to be caused by decreased carrier mobility. The dependence of mobility on temperature indicates the main role of optical phonon scattering at high temperatures. Our results provide more detailed information on carrier behavior and scattering mechanisms in WTe 2 thin films.

Extreme magnetoresistance in magnetic rare-earth monopnictides

Science.gov (United States)

Ye, Linda; Suzuki, Takehito; Wicker, Christina R.; Checkelsky, Joseph G.

2018-02-01

The acute sensitivity of the electrical resistance of certain systems to magnetic fields known as extreme magnetoresistance (XMR) has recently been explored in a new materials context with topological semimetals. Exemplified by WTe2 and rare-earth monopnictide La(Sb,Bi), these systems tend to be nonmagnetic, nearly compensated semimetals and represent a platform for large magnetoresistance driven by intrinsic electronic structure. Here we explore electronic transport in magnetic members of the latter family of semimetals and find that XMR is strongly modulated by magnetic order. In particular, CeSb exhibits XMR in excess of 1.6 ×106% at fields of 9 T whereas the magnetoresistance itself is nonmonotonic across the various magnetic phases and shows a transition from negative magnetoresistance to XMR with fields above magnetic ordering temperature TN. The magnitude of the XMR is larger than in other rare-earth monopnictides including the nonmagnetic members and follows a nonsaturating power law to fields above 30 T. We show that the overall response can be understood as the modulation of conductivity by the Ce orbital state and for intermediate temperatures can be characterized by an effective medium model. Comparison to the orbitally quenched compound GdBi supports the correlation of XMR with the onset of magnetic ordering and compensation and highlights the unique combination of orbital inversion and type-I magnetic ordering in CeSb in determining its large response. These findings suggest a paradigm for magneto-orbital control of XMR and are relevant to the understanding of rare-earth-based correlated topological materials.

Magnetoresistance of individual ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires

OpenAIRE

Butschkow, Christian H.; Reiger, Elisabeth; Geißler, Stefan; Rudolph, Andreas; Soda, Marcello; Schuh, Dieter; Woltersdorf, Georg; Wegscheider, Werner; Weiss, Dieter

2011-01-01

We investigate, angle dependent, the magnetoresistance (MR) of individual self-assembled ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires at cryogenic temperatures. The shape of the MR traces and the observed strong anisotropies in transport can be ascribed to the interplay of the negative magnetoresistance effect and a strong uniaxial anisotropy with the magnetic easy direction pointing along the wire axis. The magnetoresistance can be well described by a quantitative analysis based on the ...

Magnetoresistance of amorphous CuZr: weak localization in a three dimensional system

International Nuclear Information System (INIS)

Bieri, J.B.; Fert, A.; Creuzet, G.

1984-01-01

Observations of anomalous magnetoresistance in amorphous CuZr at low temperature are reported. The magnetoresistance can be precisely accounted for in theoretical models of localization for 3-dimensional metallic systems in the presence of strong spin-orbit interactions (with a significant additional contribution from the quenching of superconducting fluctuations at the lowest temperatures). Magnetoresistance measurements on various other systems show that such 3-dimensional localization effects are very generally observed in amorphous alloys. (author)

Hysteresis rarefaction in the Riemann problem

Czech Academy of Sciences Publication Activity Database

Krejčí, Pavel

2008-01-01

Roč. 138, - (2008), s. 1-10 ISSN 1742-6588. [International Workshop on Multi-Rate Processes and Hysteresis. Cork , 31.03.2008-05.04.2008] Institutional research plan: CEZ:AV0Z10190503 Keywords : Preisach hysteresis * Riemann problem Subject RIV: BA - General Mathematics http://iopscience.iop.org/1742-6596/138/1/012010

Anomalous electronic structure and magnetoresistance in TaAs2.

Science.gov (United States)

Luo, Yongkang; McDonald, R D; Rosa, P F S; Scott, B; Wakeham, N; Ghimire, N J; Bauer, E D; Thompson, J D; Ronning, F

2016-06-07

The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.

Comparative experiments regarding approaches to feedforward hysteresis compensation for piezoceramic actuators

International Nuclear Information System (INIS)

Gu, Guo-Ying; Zhu, Li-Min

2014-01-01

Piezoceramic actuators (PCAs) are desired devices in many micro/nano-positioning applications. The performance of PCA-based applications is severely limited by the presence of hysteresis nonlinearity. To remedy the hysteresis nonlinearity in such systems, feedforward hysteresis compensation is the most common technique. In the literature, many different feedforward hysteresis compensation approaches have been developed, but there are no comparative studies of these approaches. Focusing on the modified Prandtl-Ishlinskii model (MPIM) for asymmetric hysteresis description of piezoceramic actuators, three feedforward hysteresis compensation approaches—inverse hysteresis compensation (IHC), without inverse hysteresis compensation (WIHC), and direct inverse hysteresis compensation (DIHC)—are developed and compared in this paper. Extensive comparative experiments were conducted on a PCA-actuated stage to verify the effectiveness of the three different feedforward control approaches to hysteresis compensation. The experimental results show that the performances among the three approaches are rather similar, and the main differences among them are due to the specific implementation of each approach. (paper)

Influence of magnetostriction on hysteresis loss of electrical steel sheet

Energy Technology Data Exchange (ETDEWEB)

Tada, Hirotoshi, E-mail: tada.547.hirotoshi@jp.nssmc.com [Steel Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan); Fujimura, Hiroshi; Yashiki, Hiroyoshi [Steel Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan)

2013-01-15

To reveal influence of magnetostriction on hysteresis loss of electrical steel sheet, hysteresis loss and magnetostriction of non-oriented electrical steel sheets (NOs) with various Si and Al content and grain size and grain oriented electrical steel sheet (GO) were measured under compressive or tensile stress. Here, Si and Al content and stress were focused on as the way to change magnetostriction. Stress direction and magnetizing direction were parallel to the rolling direction. Following three main results were obtained. The first is hysteresis loss of NO with same grain size which increased with magnetostriction independently of Si and Al content and stress. The second is hysteresis loss of NO was larger than that of GO under same magnetostriction. The third is hysteresis loss of NO at magnetostriction of zero was inversely proportional to grain size. Even if the grain size of NO increased to be similar size of GO without changing texture, the hysteresis loss of NO at magnetostriction of zero would be larger than that of GO because of the difference in texture. - Highlights: Black-Right-Pointing-Pointer Hysteresis loss and magnetostriction of NO and GO were measured under stress. Black-Right-Pointing-Pointer Hysteresis loss of NO was proportional to magnetostriction. Black-Right-Pointing-Pointer Hysteresis loss of GO was proportional to magnetostriction. Black-Right-Pointing-Pointer Hysteresis loss of NO was larger than that of GO under samemagnetostriction. Black-Right-Pointing-Pointer Hysteresis loss was separated into 4 components.

Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals

Energy Technology Data Exchange (ETDEWEB)

Lv, Yang-Yang; Zhang, Bin-Bin; Yao, Shu-Hua, E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn, E-mail: zhoujian@nju.edu.cn; Zhou, Jian, E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn, E-mail: zhoujian@nju.edu.cn; Zhang, Shan-Tao; Lu, Ming-Hui [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Li, Xiao; Chen, Y. B., E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn, E-mail: zhoujian@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Chen, Yan-Feng [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructure, Nanjing University, Nanjing 210093 (China)

2016-06-13

Recently, the extremely large magnetoresistance (MR) observed in transition metal telluride, like WTe{sub 2}, attracted much attention because of the potential applications in magnetic sensor. Here, we report the observation of extremely large magnetoresistance as 3.0 × 10{sup 4}% measured at 2 K and 9 T magnetic field aligned along [001]-ZrSiS. The significant magnetoresistance change (∼1.4 × 10{sup 4}%) can be obtained when the magnetic field is titled from [001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can be understood by electron-hole compensation and the open orbital of Fermi surface. Because of these superior MR properties, ZrSiS may be used in the magnetic sensors.

Studies of colossal magnetoresistive oxides with radioactive isotopes

CERN Document Server

CERN. Geneva. ISOLDE and Neutron Time-of-Flight Experiments Committee; Amaral, V S; Araújo, J P; Butz, T; Correia, J G; Dubourdieu, C; Habermeier, H U; Lourenço, A A; Marques, J G; Da Silva, M F A; Senateur, J P; Soares, J C; Sousa, J B; Suryan, R; Tokura, Y; Tavares, P B; Tomioka, Y; Tröger, W; Vantomme, A; Vieira, J M; Wahl, U; Weiss, F P; INTC

2000-01-01

We propose to study Colossal Magnetoresistive (CMR) oxides with several nuclear techniques, which use radioactive elements at ISOLDE. Our aim is to provide local and element selective information on some of the doping mechanisms that rule electronic interactions and magnetoresistance, in a complementary way to the use of conventional characterisation techniques. Three main topics are proposed: \\\\ \\\\ a) Studies of local [charge and] structural modifications in antiferromagnetic LaMnO$_{3+ \\delta}$ and La$_{1-x}$R$_{x}$MnO$_{3}$ with R=Ca and Cd, doped ferromagnetic systems with competing interactions: - research on the lattice site and electronic characterisation of the doping element. \\\\ \\\\ b) Studies of self doped La$_{x}$R$_{1-x}$MnO$_{3+\\delta}$ systems, with oxygen and cation non-stoichiometry: -learning the role of defects in the optimisation of magnetoresistive properties. \\\\ \\\\ c) Probing the disorder and quenched random field effects in the vicinity of the charge or orbital Ordered/Ferromagnetic phase...

Stabilization and Control Models of Systems With Hysteresis Nonlinearities

Directory of Open Access Journals (Sweden)

Mihail E. Semenov

2012-05-01

Full Text Available Mechanical and economic systems with hysteresis nonlinearities are studied in article. Dissipativity condition of inverted pendulum under the hysteresis control is obtained. The solution of the optimal production strategy problem was found where price has hysteresis behaviour.

Light-induced magnetoresistance in solution-processed planar hybrid devices measured under ambient conditions

Directory of Open Access Journals (Sweden)

Sreetama Banerjee

2017-07-01

Full Text Available We report light-induced negative organic magnetoresistance (OMAR measured in ambient atmosphere in solution-processed 6,13-bis(triisopropylsilylethynylpentacene (TIPS-pentacene planar hybrid devices with two different device architectures. Hybrid electronic devices with trench-isolated electrodes (HED-TIE having a channel length of ca. 100 nm fabricated in this work and, for comparison, commercially available pre-structured organic field-effect transistor (OFET substrates with a channel length of 20 µm were used. The magnitude of the photocurrent as well as the magnetoresistance was found to be higher for the HED-TIE devices because of the much smaller channel length of these devices compared to the OFETs. We attribute the observed light-induced negative magnetoresistance in TIPS-pentacene to the presence of electron–hole pairs under illumination as the magnetoresistive effect scales with the photocurrent. The magnetoresistance effect was found to diminish over time under ambient conditions compared to a freshly prepared sample. We propose that the much faster degradation of the magnetoresistance effect as compared to the photocurrent was due to the incorporation of water molecules in the TIPS-pentacene film.

Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires.

Science.gov (United States)

Sapkota, Keshab R; Chen, Weimin; Maloney, F Scott; Poudyal, Uma; Wang, Wenyong

2016-10-14

We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. This work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.

NbSe3: Fermi surface and magnetoresistance under uniaxial stress

International Nuclear Information System (INIS)

Tessema, G.X.; Gamble, B.K.; Kuh, J.; Skove, M.J.; Lacerda, A.H.; Bennett, M.

1999-01-01

The Fermi surface of NbSe 3 below the two CDW transitions is still not very clear. Large magnetoresistance and giant quantum oscillations have been seen at low temperature below the second CDW transition. The SdH oscillations are attributed to one or several small pieces of electron or hole pockets spared by the two CDW transitions at 145 and 59 K. In a previous low field study (μ 0 H<8 T) of the transverse magnetoresistance (H in the (b,c) plane) we have shown that the extremal area of one of these pockets decreases linearly with strain, ε, vanishing at ε = 2.5%. Here we extend our study into the high magnetic field regime (pulsed 60 T) and investigate the effect of uniaxial stress on the magnetoresistance (I//H). Our high field study is consistent with the fermiology study and shows that uniaxial stress leads to the obliteration of a small closed pocket. Above 1% strain the magnetoresistance is linear with H with no sign of saturation. (orig.)

Modeling of hysteresis in magnetic multidomains

International Nuclear Information System (INIS)

Cardelli, E.; Carpentieri, M.; Faba, A.; Finocchio, G.

2014-01-01

In this paper, the analysis of multi-domain nanostructures is made by means of numerical approaches. The Landau–Lifshitz–Gilbert LLG equation is used to compute the magnetic hysteresis loops for different alternate scalar polarizations. The data computed are then used to identify the parameters of a phenomenological model, based on the extension of the Preisach model in 2-D. The identification in this case is the evaluation of the size and the position of the hysterons in the H-plane. Each hysteron is associated to a domain of the nanostructure and the assembly of hysterons reproduces with satisfactory accuracy the hysteretic behavior of the nanostructure computed by the LLG equation with an extremely reduced computational time. Some possible relationships between the magnetization nanostructure and the parameters of the hysteron are suggested. These relationship should be used for a “blind” prediction of the magnetization state of much larger magnetic structures, whose computation using the LLG equation is not possible in practice due to the enormous computational time, supposing that magnetic structures with the same aspect ratio exhibit a similar distribution of magnetic domains. The theory is applied here to an example of Permalloy nanostructure

Hysteresis phenomenon in nuclear reactor dynamics

Energy Technology Data Exchange (ETDEWEB)

Pirayesh, Behnam; Pazirandeh, Ali [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Dept. of Nuclear Engineering, Science and Research Branch; Akbari, Monireh [Shahid Rajaee Teacher Training Univ., Tehran (Iran, Islamic Republic of). Dept. of Mathematics

2017-05-15

This paper applies a nonlinear analysis method to show that hysteresis phenomenon, due to the Saddle-node bifurcation, may occur in the nuclear reactor. This phenomenon may have significant effects on nuclear reactor dynamics and can even be the beginning of a nuclear reactor accident. A system of four dimensional nonlinear ordinary differential equations was considered to study the hysteresis phenomenon in a typical nuclear reactor. It should be noted that the reactivity was considered as a nonlinear function of state variables. The condition for emerging hysteresis was investigated using Routh-Hurwitz criterion and Sotomayor's theorem for saddle node bifurcation. A numerical analysis is also provided to illustrate the analytical results.

Magnetoresistive magnetometer for space science applications

International Nuclear Information System (INIS)

Brown, P; Beek, T; Carr, C; O’Brien, H; Cupido, E; Oddy, T; Horbury, T S

2012-01-01

Measurement of the in situ dc magnetic field on space science missions is most commonly achieved using instruments based on fluxgate sensors. Fluxgates are robust, reliable and have considerable space heritage; however, their mass and volume are not optimized for deployment on nano or picosats. We describe a new magnetometer design demonstrating science measurement capability featuring significantly lower mass, volume and to a lesser extent power than a typical fluxgate. The instrument employs a sensor based on anisotropic magnetoresistance (AMR) achieving a noise floor of less than 50 pT Hz −1/2 above 1 Hz on a 5 V bridge bias. The instrument range is scalable up to ±50 000 nT and the three-axis sensor mass and volume are less than 10 g and 10 cm 3 , respectively. The ability to switch the polarization of the sensor's easy axis and apply magnetic feedback is used to build a driven first harmonic closed loop system featuring improved linearity, gain stability and compensation of the sensor offset. A number of potential geospace applications based on the initial instrument results are discussed including attitude control systems and scientific measurement of waves and structures in the terrestrial magnetosphere. A flight version of the AMR magnetometer will fly on the TRIO-CINEMA mission due to be launched in 2012. (paper)

Sign change of magnetoresistance in Gd-doped amorphous carbon granular films.

Science.gov (United States)

Ding, Shihao; Jin, Chao; Fan, Ziwei; Li, Peng; Bai, Haili

2015-11-11

Gd/C granular films with 11% Gd were fabricated by facing-target magnetron sputtering at room temperature and then annealed at 300-650 °C for 1.5 h. A magnetoresistance of -82% was obtained in the Gd/C films annealed at 650 °C at 3 K under a magnetic field of 50 kOe. A sign change of the magnetoresistance from negative to positive and then back to negative was observed in all samples as the temperature decreases. Grain boundary scattering effects, wave-function-shrinkage, cotunneling and Gd-Gd interactions account for the mechanisms of the magnetoresistance effects in different temperature regions. The sign of the magnetoresistance also varies as the magnetic field increases. At the transition temperature of 25 K, the wave-function-shrinkage effect competes with cotunneling and Gd-Gd interactions at different magnetic fields. The competition between the wave-function-shrinkage effect and the grain boundary scattering effect is approximately at the transition temperature of 100 K. The temperature range of positive magnetoresistance expands and transition temperatures are changed as the annealing temperature increases. It is related to the expansion of the temperature region for the wave-function-shrinkage effect which occurs in the Mott variable range hopping conduction mechanism.

The tunneling magnetoresistance current dependence on cross sectional area, angle and temperature

Directory of Open Access Journals (Sweden)

Z. H. Zhang

2015-03-01

Full Text Available The magnetoresistance of a MgO-based magnetic tunnel junction (MTJ was studied experimentally. The magnetoresistance as a function of current was measured systematically on MTJs for various MgO cross sectional areas and at various temperatures from 7.5 to 290.1 K. The resistance current dependence of the MTJ was also measured for different angles between the two ferromagnetic layers. By considering particle and angular momentum conservation of transport electrons, the current dependence of magnetoresistance can be explained by the changing of spin polarization in the free magnetic layer of the MTJ. The changing of spin polarization is related to the magnetoresistance, its angular dependence and the threshold current where TMR ratio equals zero. A phenomenological model is used which avoid the complicated barrier details and also describes the data.

Tunneling magnetoresistance in junctions composed of ferromagnets and time-reversal invariant topological superconductors

International Nuclear Information System (INIS)

Yan, Zhongbo; Wan, Shaolong

2016-01-01

Tunneling magnetoresistance between two ferrromagnets is an issue of fundamental importance in spintronics. In this work, we show that tunneling magnetoresistance can also emerge in junctions composed of ferromagnets and time-reversal invariant topological superconductors without spin-rotation symmetry. Here the physical origin is that when the spin-polarization direction of an injected electron from the ferromagnet lies in the same plane of the spin-polarization direction of Majorana zero modes, the electron will undergo a perfect spin-equal Andreev reflection, while injected electrons with other spin-polarization directions will be partially Andreev reflected and partially normal reflected, which consequently has a lower conductance, and therefore, the magnetoresistance effect emerges. Compared to conventional magnetic tunnel junctions, an unprecedented advantage of the junctions studied here is that arbitrary high tunneling magnetoresistance can be obtained even when the magnetization of the ferromagnets are weak and the insulating tunneling barriers are featureless. Our findings provide a new fascinating mechanism to obtain high tunneling magnetoresistance. (paper)

On the rationale for hysteresis in economic decisions

Science.gov (United States)

Rios, Luis A.; Rachinskii, Dmitrii; Cross, Rod

2017-02-01

In the social sciences there are plausible reasons to postulate that hysteresis effects are important. The available evidence, however, is predominantly at the macro level. In this paper we review the evidence regarding hysteresis in the neural processes underlying human behavior. We argue that there is a need for experimental and neuroimaging studies to fill the gap in knowledge about hysteresis processes at the micro level in the social sciences.

Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers

KAUST Repository

Manchon, Aurelien

2017-01-01

We investigate the emergence of spin Hall magnetoresistance in a magnetic bilayer composed of a normal metal adjacent to an antiferromagnet. Based on a recently derived drift diffusion equation, we show that the resistance of the bilayer depends on the relative angle between the direction transverse to the current flow and the Néel order parameter. While this effect presents striking similarities with the spin Hall magnetoresistance recently reported in ferromagnetic bilayers, its physical origin is attributed to the anisotropic spin relaxation of itinerant spins in the antiferromagnet.

Tunneling anisotropic magnetoresistance: A spin-valve-like tunnel magnetoresistance using a single magnetic layer

Czech Academy of Sciences Publication Activity Database

Gould, C.; Rüster, C.; Jungwirth, Tomáš; Girgis, E.; Schott, G. M.; Giraud, R.; Brunner, K.; Schmidt, G.; Molenkamp, L. W.

2004-01-01

Roč. 93, č. 11 (2004), 117203/1-117203/4 ISSN 0031-9007 R&D Projects: GA ČR GA202/02/0912 Institutional research plan: CEZ:AV0Z1010914 Keywords : semiconductor spintronics * tunneling anisotropic magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.218, year: 2004

Enhanced magnetoresistance in the binary semimetal NbAs2 due to improved crystal quality

Science.gov (United States)

Yokoi, K.; Murakawa, H.; Komada, M.; Kida, T.; Hagiwara, M.; Sakai, H.; Hanasaki, N.

2018-02-01

We have observed an extremely large magnetoresistance exceeding 1.9 million at 1.7 K at 40 T for a single crystal of the binary semimetal NbAs2. The magnetoresistive behavior for this compound is quantitatively reproduced by a semiclassical two-carrier model in which the significant enhancement of magnetoresistance is attributed to the almost full compensation of the hole and electron densities (0.994 6 ×105cm2 /V .s ). Our results indicate that binary semimetals with higher carrier densities have a great potential for exhibiting a further divergent increase in magnetoresistance merely through an improvement in crystal quality.

Adaptive Hysteresis Band Current Control (AHB) with PLL of Grid Side Converter-Based Wind Power Generation System

DEFF Research Database (Denmark)

Guo, Yougui; Zeng, Ping; Li, Lijuan

2011-01-01

Adaptive hysteresis band current control(AHB CC) is used to control the three-phase grid currents by means of grid side converter in wind power generation system in this paper. AHB has reached the good purpose with PLL (Lock phase loop). First the mathematical models of each part are given......, transformer and grid, and control parts, etc. The simulation results have verified that the control strategy is feasible to fit for control of gird currents, active power, reactive power and DC-link voltage in wind power generation system....

Development of a real-time closed-loop micro-/nano-positioning system embedded with a capacitive sensor

International Nuclear Information System (INIS)

Shiou, Fang-Jung; Chiang, Chia-Jui; Liou, Ke-Jhen; Liao, Shu-Chung; Chen, Chao-Jung; Liou, Huay-Chung

2010-01-01

The hysteresis and nonlinearity of the PZT is an actual problem in the piezo-driven micro-/nano-positioning stage, especially for the open-loop positioning stage. The study presents the development of an NI cRIO9074-based real-time closed-loop micro-/nano-positioning system, to overcome the problem of the hysteresis and nonlinearity of a PZT and to increase the positioning speed of the positioning stage. The developed system mainly consists of a piezoelectric actuator, a bridge-type hinge mechanism for displacement magnification, a micro-/nano-positioning stage body, a capacitive sensor system, an NI cRIO9074 real-time control unit with FPGA chip and a PC. After executing the optimization analysis of the displacement, stress and the frequency, using the ANSYS software, the dimensions of the stage body have been designed and determined. A set of software written with the LabView programming language was developed to construct the real-time PID closed-loop control of the developed positioning system. Based on the test results, the designed closed-loop micro-/nano-positioning system was capable of precision positioning within the travel of 119.08 µm with maximum stage tilting angle at 25 µrad. The steady-state positioning deviation of the stage is about ±2 nm in the step-positioning test. In the transient slope-tracing test at a tracing speed of 5 µm s −1 , an error of about ±100 nm is observed

Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires

International Nuclear Information System (INIS)

Liang, J.; Wang, J.; Cooley, B. J.; Rench, D. W.; Samarth, N.; Paul, A.; Dellas, N. S.; Mohney, S. E.; Engel-Herbert, R.

2012-01-01

We report four probe measurements of the low field magnetoresistance (MR) in single core/shell GaAs/MnAs nanowires (NWs) synthesized by molecular beam epitaxy, demonstrating clear signatures of anisotropic magnetoresistance that track the field-dependent magnetization. A comparison with micromagnetic simulations reveals that the principal characteristics of the magnetoresistance data can be unambiguously attributed to the nanowire segments with a zinc blende GaAs core. The direct correlation between magnetoresistance, magnetization, and crystal structure provides a powerful means of characterizing individual hybrid ferromagnet/semiconductor nanostructures.

Thickness Dependent Interlayer Magnetoresistance in Multilayer Graphene Stacks

Directory of Open Access Journals (Sweden)

S. C. Bodepudi

2016-01-01

Full Text Available Chemical Vapor Deposition grown multilayer graphene (MLG exhibits large out-of-plane magnetoresistance due to interlayer magnetoresistance (ILMR effect. It is essential to identify the factors that influence this effect in order to explore its potential in magnetic sensing and data storage applications. It has been demonstrated before that the ILMR effect is sensitive to the interlayer coupling and the orientation of the magnetic field with respect to the out-of-plane (c-axis direction. In this work, we investigate the role of MLG thickness on ILMR effect. Our results show that the magnitude of ILMR effect increases with the number of graphene layers in the MLG stack. Surprisingly, thicker devices exhibit field induced resistance switching by a factor of at least ~107. This effect persists even at room temperature and to our knowledge such large magnetoresistance values have not been reported before in the literature at comparable fields and temperatures. In addition, an oscillatory MR effect is observed at higher field values. A physical explanation of this effect is presented, which is consistent with our experimental scenario.

Magnetoresistance stories of double perovskites

Indian Academy of Sciences (India)

2015-05-28

May 28, 2015 ... Tunnelling magnetoresistance (TMR) in polycrystalline double perovskites has been an important research topic for more than a decade now, where the nature of the insulating tunnel barrier is the core issue of debate. Other than the nonmagnetic grain boundaries as conventional tunnel barriers, intragrain ...

Superconductivity in Pb inverse opal

International Nuclear Information System (INIS)

Aliev, Ali E.; Lee, Sergey B.; Zakhidov, Anvar A.; Baughman, Ray H.

2007-01-01

Type-II superconducting behavior was observed in highly periodic three-dimensional lead inverse opal prepared by infiltration of melted Pb in blue (D = 160 nm), green (D = 220 nm) and red (D = 300 nm) opals and followed by the extraction of the SiO 2 spheres by chemical etching. The onset of a broad phase transition (ΔT = 0.3 K) was shifted from T c = 7.196 K for bulk Pb to T c = 7.325 K. The upper critical field H c2 (3150 Oe) measured from high-field hysteresis loops exceeds the critical field for bulk lead (803 Oe) fourfold. Two well resolved peaks observed in the hysteresis loops were ascribed to flux penetration into the cylindrical void space that can be found in inverse opal structure and into the periodic structure of Pb nanoparticles. The red inverse opal shows pronounced oscillations of magnetic moment in the mixed state at low temperatures, T 0.9T c has been observed for all of the samples studied. The magnetic field periodicity of resistivity modulation is in good agreement with the lattice parameter of the inverse opal structure. We attribute the failure to observe pronounced modulation in magneto-resistive measurement to difficulties in the precision orientation of the sample along the magnetic field

Magnetoresistance Probe of Ultrathin Mn5Ge3 Films with Anderson Weak Localization

International Nuclear Information System (INIS)

Li-Jun, Chen; De-Yong, Wang; Qing-Feng, Zhan; Wei, He; Qing-An, Li

2008-01-01

We present the magnetoresistance measurements of ultrathin Mn 5 Ge 3 films with different thicknesses at low temperatures. Owing to the lattice mismatch between Mn 5 Ge 3 and Ge (111), the thickness of Mn 5 Ge 3 films has a significant effect on the magnetoresistance. When the thickness of Mn is more than 72 monolayers (MLs), the magnetoresistance of the Mn 5 Ge 3 films appears a peak at about 6kOe, which shows that the magnetoresistance results from the Anderson weak localization effect and the variable range hopping in the presence of a magnetic field. The magnetic and semiconducting properties indicate that the Mn 5 Ge 3 film is a potential material for spin injection. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Oscillations in magnetoresistance and interlayer coupling in magnetic sandwich structures

International Nuclear Information System (INIS)

Barnas, J.; Bulka, B.

1997-01-01

Kubo formalism is used to calculate the magnetoresistance due to magnetization rotation in a structure consisting two magnetic films separated by nonmagnetic layer. In the approximation of an uniform relaxation time of each layer, the oscillatory term in magnetoresistance corresponds to the oscillation period which depends on the potential barriers at the interfaces. This period is longer than the oscillation period observed in the coupling parameter. (author)

Spin–orbit coupling induced magnetoresistance oscillation in a dc biased two-dimensional electron system

International Nuclear Information System (INIS)

Wang, C M; Lei, X L

2014-01-01

We study dc-current effects on the magnetoresistance oscillation in a two-dimensional electron gas with Rashba spin-orbit coupling, using the balance-equation approach to nonlinear magnetotransport. In the weak current limit the magnetoresistance exhibits periodical Shubnikov-de Haas oscillation with changing Rashba coupling strength for a fixed magnetic field. At finite dc bias, the period of the oscillation halves when the interbranch contribution to resistivity dominates. With further increasing current density, the oscillatory resistivity exhibits phase inversion, i.e., magnetoresistivity minima (maxima) invert to maxima (minima) at certain values of the dc bias, which is due to the current-induced magnetoresistance oscillation. (paper)

Domain wall magnetoresistance in BiFeO3 thin films measured by scanning probe microscopy.

Science.gov (United States)

Domingo, N; Farokhipoor, S; Santiso, J; Noheda, B; Catalan, G

2017-08-23

We measure the magnetotransport properties of individual 71° domain walls in multiferroic BiFeO 3 by means of conductive-atomic force microscopy (C-AFM) in the presence of magnetic fields up to one Tesla. The results suggest anisotropic magnetoresistance at room temperature, with the sign of the magnetoresistance depending on the relative orientation between the magnetic field and the domain wall plane. A consequence of this finding is that macroscopically averaged magnetoresistance measurements for domain wall bunches are likely to underestimate the magnetoresistance of each individual domain wall.

Stereo Hysteresis Revisited

Directory of Open Access Journals (Sweden)

Christopher Tyler

2012-05-01

Full Text Available One of the most fascinating phenomena in stereopsis is the profound hysteresis effect reported by Fender and Julesz (1967, in which the depth percept persisted with increasing disparity long past the point at which depth was recovered with decreasing disparity. To control retinal disparity without vergence eye movements, they stabilized the stimuli on the retinas with an eye tracker. I now report that stereo hysteresis can be observed directly in printed stereograms simply by rotating the image. As the stereo image rotates, the horizontal disparities rotate to become vertical, then horizontal with inverted sign, and then vertical again before returning to the original orientation. The depth shows an interesting popout effect, almost as though the depth was turning on and off rapidly, despite the inherently sinusoidal change in the horizontal disparity vector. This stimulus was generated electronically in a circular format so that the random-dot field could be dynamically replaced, eliminating any cue to cyclorotation. Noise density was scaled with eccentricity to fade out the stimulus near fixation. For both the invariant and the dynamic noise, profound hysteresis of several seconds delay was found in six observers. This was far longer than the reaction time to respond to changes in disparity, which was less than a second. Purely horizontal modulation of disparity to match the horizontal vector component of the disparity rotation did not show the popout effect, which thus seems to be a function of the interaction between horizontal and vertical disparities and may be attributable to depth interpolation processes.

Magnetoresistance of tungsten thin wafer at the multichannel surface scattering of conduction electrons

International Nuclear Information System (INIS)

Lutsishin, P.P.; Nakhodkin, T.N.

1982-01-01

The magnetoresistance of tungsten thin wafer with the (110) surface was studied at the adsorption of tungsten dioxide. The method of low-energy electron diffraction was used to study the symmetry of ordered surface structures. Using the method of the magnetoresistance measurement the character of the scattering of conduction electrons was investigated. THe dependence of magnetoresistance on the surface concentration of tungsten dioxide correlated w1th the structure of the surface layer of atoms, what was explained with allowance for diffraction of conduction electrons at the metal boundary. The magnetoresistance maximum for the (2x2) structure, which characterised decrease in surface conduction under the conditions of static skin effect, was explained by multichannel mirror reflection with the recombinations of electron and ho.le sections of Fermi Surface

Observation of magnetic polarons in the magnetoresistive pyrochlore Lu2V2O7

International Nuclear Information System (INIS)

Storchak, Vyacheslav G; Brewer, Jess H; Eshchenko, Dmitry G; Mengyan, Patrick W; Zhou Haidong; Wiebe, Christopher R

2013-01-01

Materials that exhibit colossal magnetoresistance (CMR) have attracted much attention due to their potential technological applications. One particularly interesting model for the magnetoresistance of low-carrier-density ferromagnets involves mediation by magnetic polarons (MP)—electrons localized in nanoscale ferromagnetic ‘droplets’ by their exchange interaction. However, MP have not previously been directly detected and their size has been difficult to determine from macroscopic measurements. In order to provide this crucial information, we have carried out muon spin rotation measurements on the magnetoresistive semiconductor Lu 2 V 2 O 7 in the temperature range from 2 to 300 K and in magnetic fields up to 7 T. Magnetic polarons with characteristic radius R ≈ 0.4 nm are detected below about 100 K, where Lu 2 V 2 O 7 exhibits CMR; at higher temperature, where the magnetoresistance vanishes, these MP also disappear. This observation confirms the MP-mediated model of CMR and reveals the microscopic size of the MP in magnetoresistive pyrochlores. (paper)

Magnetic and magnetotransport properties of Fe nanoparticles embedded in Ag matrix

Energy Technology Data Exchange (ETDEWEB)

Sarmiento, G. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), Apartado 644, 48080 Bilbao (Spain); Garcia Prieto, A. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), Apartado 644, 48080 Bilbao (Spain); Orue, I. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), Apartado 644, 48080 Bilbao (Spain); Fdez-Gubieda, M.L. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), Apartado 644, 48080 Bilbao (Spain)]. E-mail: malu@we.lc.ehu.es

2005-04-15

Fe{sub 20}Ag{sub 80} and Fe{sub 30}Ag{sub 70} granular thin films have been prepared by the pulsed laser deposition technique under different parameter conditions of pulse frequency and target angular speed. Their influence on the microstructure of the sample, through the analysis of the hysteresis loops, magnetotransport response and magnetooptical Kerr effect, has been investigated. The Fe{sub 20}Ag{sub 80} samples present a superparamagnetic phase, composed of spherical Fe clusters with a mean diameter of 3nm. The number of Fe nanoparticles increases as both laser pulse frequency and target angular speed increase, thus enhancing their giant magnetoresistance response. The Fe{sub 30}Ag{sub 70} thin films have anisotropic magnetic behaviour and their magnetotransport measurements show giant magnetoresistance and extraordinary Hall effect. These anisotropies suggest the presence of Fe planar particles, which give rise to shape magnetic anisotropy that increases with increasing the target angular speed for a given laser pulse frequency. The planar shape of the Fe particles could be in the origin of the dominant extraordinary Hall effect.

Magnetic and magnetotransport properties of Fe nanoparticles embedded in Ag matrix

International Nuclear Information System (INIS)

Sarmiento, G.; Garcia Prieto, A.; Orue, I.; Fdez-Gubieda, M.L.

2005-01-01

Fe 20 Ag 80 and Fe 30 Ag 70 granular thin films have been prepared by the pulsed laser deposition technique under different parameter conditions of pulse frequency and target angular speed. Their influence on the microstructure of the sample, through the analysis of the hysteresis loops, magnetotransport response and magnetooptical Kerr effect, has been investigated. The Fe 20 Ag 80 samples present a superparamagnetic phase, composed of spherical Fe clusters with a mean diameter of 3nm. The number of Fe nanoparticles increases as both laser pulse frequency and target angular speed increase, thus enhancing their giant magnetoresistance response. The Fe 30 Ag 70 thin films have anisotropic magnetic behaviour and their magnetotransport measurements show giant magnetoresistance and extraordinary Hall effect. These anisotropies suggest the presence of Fe planar particles, which give rise to shape magnetic anisotropy that increases with increasing the target angular speed for a given laser pulse frequency. The planar shape of the Fe particles could be in the origin of the dominant extraordinary Hall effect

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

Directory of Open Access Journals (Sweden)

Torres C.

2013-01-01

Full Text Available Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer’s formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

Energy Technology Data Exchange (ETDEWEB)

Zhuang, Shendong; Tang, Nujiang; Chen, Zhuo, E-mail: zchen@nju.edu.cn [School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, No. 22 Hankou Road, Nanjing, Jiangsu, 210093 (China); Chen, Yan; Xia, Yidong [Department of Materials Science and Engineering, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, No. 22 Hankou Road, Nanjing University, Nanjing, Jiangsu, 210093 (China); Xu, Xiaoyong; Hu, Jingguo, E-mail: jghu@yzu.edu.cn [School of Physics Science and Technology, Yangzhou University, No. 180 Siwangting Road, Yangzhou, Jiangsu, 225002 (China)

2016-04-15

Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.

Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

International Nuclear Information System (INIS)

Zhuang, Shendong; Tang, Nujiang; Chen, Zhuo; Chen, Yan; Xia, Yidong; Xu, Xiaoyong; Hu, Jingguo

2016-01-01

Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.

Efficient modeling of vector hysteresis using fuzzy inference systems

International Nuclear Information System (INIS)

Adly, A.A.; Abd-El-Hafiz, S.K.

2008-01-01

Vector hysteresis models have always been regarded as important tools to determine which multi-dimensional magnetic field-media interactions may be predicted. In the past, considerable efforts have been focused on mathematical modeling methodologies of vector hysteresis. This paper presents an efficient approach based upon fuzzy inference systems for modeling vector hysteresis. Computational efficiency of the proposed approach stems from the fact that the basic non-local memory Preisach-type hysteresis model is approximated by a local memory model. The proposed computational low-cost methodology can be easily integrated in field calculation packages involving massive multi-dimensional discretizations. Details of the modeling methodology and its experimental testing are presented

Hysteresis properties of conventionally annealed and Joule-heated nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloys

International Nuclear Information System (INIS)

Tiberto, P.; Basso, V.; Beatrice, C.; Bertotti, G.

1996-01-01

The dependence of magnetic properties on the thermal treatment used to induce the amorphous-to-nanocrystalline transformation in Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy has been studied. Quasi-static hysteresis loops and initial permeability measurements were performed on nanocrystalline samples obtained by conventional annealing and Joule heating. A comparison between the magnetic properties of nanocrystalline samples obtained by the two heating procedures is presented. (orig.)

Crossover of angular dependent magnetoresistance with the metal-insulator transition in colossal magnetoresistive manganite films

DEFF Research Database (Denmark)

Chen, Yunzhong; Sun, J.R.; Zhao, T.Y.

2009-01-01

The temperature and magnetic field dependence of angular dependent magnetoresistance (AMR) along two orthogonal directions ([100] and [01]) was investigated in a charge-orbital-ordered Sm0.5Ca0.5MnO3 (SCMO) film grown on (011)-oriented SrTiO3 substrates. A dramatic decrease of AMR magnitude in bo...

Isothermal anisotropic magnetoresistance in antiferromagnetic metallic IrMn.

Science.gov (United States)

Galceran, R; Fina, I; Cisneros-Fernández, J; Bozzo, B; Frontera, C; López-Mir, L; Deniz, H; Park, K-W; Park, B-G; Balcells, Ll; Martí, X; Jungwirth, T; Martínez, B

2016-10-20

Antiferromagnetic spintronics is an emerging field; antiferromagnets can improve the functionalities of ferromagnets with higher response times, and having the information shielded against external magnetic field. Moreover, a large list of aniferromagnetic semiconductors and metals with Néel temperatures above room temperature exists. In the present manuscript, we persevere in the quest for the limits of how large can anisotropic magnetoresistance be in antiferromagnetic materials with very large spin-orbit coupling. We selected IrMn as a prime example of first-class moment (Mn) and spin-orbit (Ir) combination. Isothermal magnetotransport measurements in an antiferromagnetic-metal(IrMn)/ferromagnetic-insulator thin film bilayer have been performed. The metal/insulator structure with magnetic coupling between both layers allows the measurement of the modulation of the transport properties exclusively in the antiferromagnetic layer. Anisotropic magnetoresistance as large as 0.15% has been found, which is much larger than that for a bare IrMn layer. Interestingly, it has been observed that anisotropic magnetoresistance is strongly influenced by the field cooling conditions, signaling the dependence of the found response on the formation of domains at the magnetic ordering temperature.

The study of the sample size on the transverse magnetoresistance of bismuth nanowires

International Nuclear Information System (INIS)

Zare, M.; Layeghnejad, R.; Sadeghi, E.

2012-01-01

The effects of sample size on the galvanomagnetice properties of semimetal nanowires are theoretically investigated. Transverse magnetoresistance (TMR) ratios have been calculated within a Boltzmann Transport Equation (BTE) approach by specular reflection approximation. Temperature and radius dependence of the transverse magnetoresistance of cylindrical Bismuth nanowires are given. The obtained values are in good agreement with the experimental results, reported by Heremans et al. - Highlights: ► In this study effects of sample size on the galvanomagnetic properties of Bi. ► Nanowires were explained by Parrott theorem by solving the Boltzmann Transport Equation. ► Transverse magnetoresistance (TMR) ratios have been measured by specular reflection approximation. ► Temperature and radius dependence of the transverse magnetoresistance of cylindrical Bismuth nanowires are given. ► The obtained values are in good agreement with the experimental results, reported by Heremans et al.

Tuning the magnetoresistance of ultrathin WTe2 sheets by electrostatic gating.

Science.gov (United States)

Na, Junhong; Hoyer, Alexander; Schoop, Leslie; Weber, Daniel; Lotsch, Bettina V; Burghard, Marko; Kern, Klaus

2016-11-10

The semimetallic, two-dimensional layered transition metal dichalcogenide WTe 2 has raised considerable interest due to its huge, non-saturating magnetoresistance. While for the origin of this effect, a close-to-ideal balance of electrons and holes has been put forward, the carrier concentration dependence of the magnetoresistance remains to be clarified. Here, we present a detailed study of the magnetotransport behaviour of ultrathin, mechanically exfoliated WTe 2 sheets as a function of electrostatic back gating. The carrier concentration and mobility, determined using the two band model and analysis of the Shubnikov-de Haas oscillations, indicate enhanced surface scattering for the thinnest sheets. By the back gate action, the magnetoresistance could be tuned by up to ∼100% for a ∼13 nm-thick WTe 2 sheet.

Resistance and magnetoresistance of annealed amorphous carbon films containing Fe3C nanograins

International Nuclear Information System (INIS)

Lee Yuhua; Han Taichun; Wur, C.-S.

2004-01-01

The temperature-dependent resistance and the field-dependent magnetoresistance were measured for films annealed at temperatures from 250 deg. C to 550 deg. C for a period of 60 min. Results of temperature-dependent resistance show electrical tunneling conductance in the films annealed at T a =250 deg. C and 350 deg. C only. The largest magnetoresistance ratio (MR) of 23% at temperature T=2 K was observed for T a =350 deg. C. The variations of both the temperature dependence of resistance and the magnetoresistance with the annealing temperature are discussed

Study of the temperature dependence of giant magnetoresistance in metallic granular composite

International Nuclear Information System (INIS)

Ju Sheng; Li, Z.-Y.

2002-01-01

The temperature dependence of the giant magnetoresistance of metallic granular composite is studied. It is considered that the composite contains both large magnetic grains with surface spin S' and small magnetic impurities. It is found that the decrease of surface spin S' of grain is the main cause of an almost linear decrease of giant magnetoresistance with the increase of temperature in high temperature range. The magnetic impurities, composed of several atoms, lead to an almost linear increase of the giant magnetoresistance with the decrease of temperature in low temperature range. Our calculations are in good agreement with recent experimental data for metallic nanogranular composites

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

Science.gov (United States)

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Anisotropic magnetoresistance and tunneling magnetoresistance of conducting filaments in NiO with different resistance states

Science.gov (United States)

Zhao, Diyang; Qiao, Shuang; Luo, Yuxiang; Chen, Aitian; Zhang, Pengfei; Zheng, Ping; Sun, Zhong; Guo, Minghua; Chiang, F.-K.; Wu, Jian; Luo, Jianlin; Li, Jianqi; Wang, Yayu; Zhao, Yonggang; Tsinghua University Team; Chinese Academy of Sciences Collaboration

Resistive switching (RS) effect in conductor/insulator/conductor thin-film stacks has attracted much attention due to its interesting physics and potentials for applications. NiO is one of the most representative systems and its RS effect has been generally explained by the formation and rupture of Ni related conducting filaments, which are very unique since they are formed by electric forming process. We study the MR behaviors in NiO RS films with different resistance states. Rich and interesting MR behaviors were observed, including the normal and anomalous anisotropic magnetoresistance (AMR) and tunneling magnetoresistance (TMR), etc., which provide new insights into the nature of the filaments and their evolution in the resistive switching process. First-principles calculation reveals the essential role of oxygen migration into the filaments during the RESET process and can account for the experimental results. Our work provides a new avenue for the exploration of the conducting filaments in RS materials, and is significant for understanding the RS mechanism as well as multifunctional device design.

Magnetic transmission gear finite element simulation with iron pole hysteresis

Science.gov (United States)

Filippini, Mattia; Alotto, Piergiorgio; Glehn, Gregor; Hameyer, Kay

2018-04-01

Ferromagnetic poles in a magnetic transmission gear require particular attention during their design process. Usually, during the numerical simulation of these devices the effects of hysteresis for loss estimation are neglected and considered only during post-processing calculations. Since the literature lacks hysteresis models, this paper adopts a homogenized hysteretic model able to include eddy current and hysteresis losses in 2D laminated materials for iron poles. In this article the results related to the hysteresis in a magnetic gear are presented and compared to the non-hysteretic approach.

Negative and positive magnetoresistance in bilayer graphene: Effects of weak localization and charge inhomogeneity

International Nuclear Information System (INIS)

Chen Yungfu; Bae, Myung-Ho; Chialvo, Cesar; Dirks, Travis; Bezryadin, Alexey; Mason, Nadya

2011-01-01

We report measurements of magnetoresistance in bilayer graphene as a function of gate voltage (carrier density) and temperature. We examine multiple contributions to the magnetoresistance, including those of weak localization (WL), universal conductance fluctuations (UCF), and inhomogeneous charge transport. A clear WL signal is evident at all measured gate voltages (in the hole doped regime) and temperature ranges (from 0.25 to 4.3 K), and the phase coherence length extracted from the WL data does not saturate at low temperatures. The WL data is fit to demonstrate that the electron-electron Nyquist scattering is the major source of phase decoherence. A decrease in UCF amplitude with increase in gate voltage and temperature is shown to be consistent with a corresponding decrease in the phase coherence length. In addition, a weak positive magnetoresistance at higher magnetic fields is observed, and attributed to inhomogeneous charge transport. -- Research highlights: → Weak localization theory describes low-field magnetoresistance in bilayer graphene. → Electron-electron Nyquist scattering limits phase coherence in bilayer graphene. → Positive magnetoresistance reveals charge inhomogeneity in bilayer graphene.

Hysteresis in the phase transition of chocolate

Science.gov (United States)

Ren, Ruilong; Lu, Qunfeng; Lin, Sihua; Dong, Xiaoyan; Fu, Hao; Wu, Shaoyi; Wu, Minghe; Teng, Baohua

2016-01-01

We designed an experiment to reproduce the hysteresis phenomenon of chocolate appearing in the heating and cooling process, and then established a model to relate the solidification degree to the order parameter. Based on the Landau-Devonshire theory, our model gave a description of the hysteresis phenomenon in chocolate, which lays the foundations for the study of the phase transition behavior of chocolate.

Hysteresis in audiovisual synchrony perception.

Directory of Open Access Journals (Sweden)

Jean-Rémy Martin

Full Text Available The effect of stimulation history on the perception of a current event can yield two opposite effects, namely: adaptation or hysteresis. The perception of the current event thus goes in the opposite or in the same direction as prior stimulation, respectively. In audiovisual (AV synchrony perception, adaptation effects have primarily been reported. Here, we tested if perceptual hysteresis could also be observed over adaptation in AV timing perception by varying different experimental conditions. Participants were asked to judge the synchrony of the last (test stimulus of an AV sequence with either constant or gradually changing AV intervals (constant and dynamic condition, respectively. The onset timing of the test stimulus could be cued or not (prospective vs. retrospective condition, respectively. We observed hysteretic effects for AV synchrony judgments in the retrospective condition that were independent of the constant or dynamic nature of the adapted stimuli; these effects disappeared in the prospective condition. The present findings suggest that knowing when to estimate a stimulus property has a crucial impact on perceptual simultaneity judgments. Our results extend beyond AV timing perception, and have strong implications regarding the comparative study of hysteresis and adaptation phenomena.

Anomalies of magnetoresistance of compounds with atomic clusters RB12 (R = Ho, Er, Tm, Lu)

International Nuclear Information System (INIS)

Sluchanko, N. E.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Samarin, N. A.; Sluchanko, D. N.; Dukhnenko, A. V.; Levchenko, A. V.

2009-01-01

The magnetoresistance and magnetization of single-crystal samples of rare-earth dodecaborides RB 12 (R = Ho, Er, Tm, Lu) have been measured at low temperatures (1.8-35 K) in a magnetic field of up to 70 kOe. The effect of positive magnetoresistance that obeys the Kohler's rule Δρ/ρ = f(ρ(0, 300 K)H/ρ(0, T)) is observed for the nonmagnetic metal LuB 12 . In the magnetic dodecaborides HoB 12 , ErB 12 , and TmB 12 , three characteristic regimes of the magnetoresistance behavior have been revealed: the positive magnetoresistance effect similar to the case of LuB 12 is observed at T > 25 K; in the range T N ≤ T ≤ 15 K, the magnetoresistance becomes negative and depends quadratically on the external magnetic field; and, finally, upon the transition to the antiferromagnetic phase (T N ), the positive magnetoresistance is again observed and its amplitude reaches 150% for HoB 12 . It has been shown that the observed anomalies of negative magnetoresistance in the paramagnetic phase can be explained within the Yosida model of conduction electron scattering by localized magnetic moments. The performed analysis confirms the formation of spin-polaron states in the 5d band in the vicinity of rare-earth ions in paramagnetic and magnetically ordered phases of RB 12 and makes it possible to reveal a number of specific features in the transformation of the magnetic structure of the compounds under investigation

Magnetoresistance and magnetic breakdown phenomenon in amorphous magnetic alloys

International Nuclear Information System (INIS)

Chen Hui-yu; Gong Xiao-yu

1988-01-01

Transverse magnetoresistance in amorphous magnetic alloys (Fe/sub 1-//sub x/CO/sub x/) 82 Cu/sub 0.4/Si/sub 4.4/B/sub 13.2/ were measured at room temperature and in the magnetic field range 0--15 kOe. For large magnetic field, three different functional dependences of magnetoresistance on magnetic field strength have been found as follows: (1) Δrho/rho approaches saturation. (2) Δrho/rho increases proportionally to H 2 . (3) For x = 0.15, a sharp Δrho/rho peak appears at a certain magnetic field strength in spatial angular orientation of both magnetic field and electric currents. Case (3) is a magnetic breakdown phenomenon. Magnetic breakdown occurs at the gap between the spin-up and spin-down sheets of the Fermi surface. This gap is the spin-orbit gap and its magnitude is a sensitive function of magnetization. Hence the magnitude and width of the magnetoresistance peak and the magnetic field strength at the peak point are functions of angular orientation of both magnetic field and electric current

Intrinsic Low Hysteresis Touch Mode Capacitive Pressure Sensor

DEFF Research Database (Denmark)

Fragiacomo, Giulio; Pedersen, Thomas; Hansen, Ole

2011-01-01

Hysteresis has always been one of the main concerns when fabricating touch mode capacitive pressure sensors (TMCPS). This phenomenon can be fought at two different levels: during fabrication or after fabrication with the aid of a dedicated signal conditioning circuit. We will describe...... a microfabrication step that can be introduced in order to reduce drastically the hysteresis of this type of sensors without compromising their sensitivity. Medium-high range (0 to 10 bar absolute pressure) TMCPS with a capacitive signal span of over 100pF and less than 1 % hysteresis in the entire pressure range...

Wheatstone bridge giant-magnetoresistance based cell counter.

Science.gov (United States)

Lee, Chiun-Peng; Lai, Mei-Feng; Huang, Hao-Ting; Lin, Chi-Wen; Wei, Zung-Hang

2014-07-15

A Wheatstone bridge giant magnetoresistance (GMR) biosensor was proposed here for the detection and counting of magnetic cells. The biosensor was made of a top-pinned spin-valve layer structure, and it was integrated with a microchannel possessing the function of hydrodynamic focusing that allowed the cells to flow in series one by one and ensured the accuracy of detection. Through measuring the magnetoresistance variation caused by the stray field of the magnetic cells that flowed through the microchannel above the GMR biosensor, we can not only detect and count the cells but we can also recognize cells with different magnetic moments. In addition, a magnetic field gradient was applied for the separation of different cells into different channels. Copyright © 2014 Elsevier B.V. All rights reserved.

As cast precipitation microstructures in twin-roller melt-spun Cu{sub 90}Co{sub 10} alloys

Energy Technology Data Exchange (ETDEWEB)

Núñez-Coavas, H. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Pozo-López, G., E-mail: gpozo@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Instituto de Física Enrique Gaviola – CONICET (Argentina); Condó, A.M. [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina); Urreta, S.E. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); and others

2016-12-15

As cast Cu{sub 90}Co{sub 10} ribbons rapidly solidified by twin-roller melt spinning, exhibit special microstructure features. This processing method provides scenarios where a different phase selection takes place; coherent Co precipitates form directly from solidification, with neither a spinodal-like composition oscillation nor a discontinuously precipitated laminar phase. Samples are processed at tangential wheel speeds of 10 m/s (V10), 15 m/s (V15), 20 m/s (V20) and 30 m/s (V30). Microstructures resulting from this single step process are characterized and the hysteresis properties and the magnetoresistance effects evaluated. Samples V30 have a quite uniform density of coherent precipitates, with a narrow size distribution around 4 nm. On contrary, non-uniform precipitate distributions are found in samples cooled at lower rates; zones with a high density of coherent Co-rich precipitates are found forming colonies. These colonies are consistent with the extended compositional fluctuations occurring during very early stages in the cooling process. Samples may exhibit wide (V10) and even bimodal (V15) size distributions. Only samples V30 behave close to the ideal superparamagnetism. Samples V20 present relatively large coercivity and relative remanence and behave as an interacting superparamagnet, while the hysteresis loops of ribbons cooled at lower rates exhibit a ferromagnetic contribution in addition to the superparamagnetic-like one. This ferromagnetic component arises from blocked precipitates, larger than the upper bound size for superparamagnetic behavior at 300 K (12 nm). Room temperature magnetoresistance values associated to granular scattering units decrease as the mean precipitate size increases, but they remain below 2%, which is lower than that measured in samples annealed after rapid solidification, indicating that in this latter case contributions from the spinodally segregated matrix take place in addition to that of Co granules. - Highlights: �

Plastic deformation and hysteresis for hydrogen storage in Pd–Rh alloys

Energy Technology Data Exchange (ETDEWEB)

Cappillino, P.J., E-mail: pcappil@sandia.gov [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States); Lavernia, E.J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Ong, M.D. [Department of Physics, Whitworth University, Spokane, WA 99251 (United States); Wolfer, W.G.; Yang, N.Y. [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States)

2014-02-15

Highlights: • Experimental evidence of plastic work resulting from hydriding of palladium is presented. • A model of this plastic work was generated and correlated to hysteresis losses. • This hysteresis is thought to be important to the lifetime of hydrogen storage materials. • Yield strength values predicted by this model agree with measured hardness. -- Abstract: The hysteresis observed when reversibly absorbing and desorbing hydrogen in metals is currently not fully understood. In general, a hysteresis represents energy that is dissipated during a cycle, but the underlying mechanism of dissipation is still uncertain. It has been suggested that the hysteresis arises either from plastic work, or from elastic strains associated with the accommodation of the hydride phase, or from both. We present here experimental evidence that implicates plastic deformation as the cause of the hysteresis in a Pd–Rh alloy. The plastic work is evident from the increased dislocation density, from the accumulation of surface steps from slip bands, from line broadening of X-ray diffraction peaks, and from an increase in hardness with the number of hydriding cycles. A model of this plastic work is developed that depends on an effective yield strength. When this model is correlated with the measured hysteresis losses, two values are found for the effective yield strength. The lower value is shown to agree with yield strength values derived from Vickers hardness measurements. The hysteresis areas for repeated cycles of absorption and desorption decrease little with the number of cycles which is reminiscent of the plastic deformation hysteresis during low-cycle fatigue of metals. This similarity further confirms the plastic nature of the hydriding hysteresis.

Domain wall magnetoresistance in nanowires: Dependence on geometrical factors and material parameters

International Nuclear Information System (INIS)

Allende, S.; Retamal, J.C.; Altbir, D.; D'Albuquerque e Castro, J.

2014-01-01

The magnetoresistance associated with the presence of domain walls in metallic nanowires is investigated as a function of geometrical parameters, corresponding to the wall thickness and the nanowire width, as well as of material parameters, such as the band filling and the exchange interaction. Transport across the structure is described within Landauer formalism. Both cases of saturated and non-saturated ferromagnets are considered, and in all of them the contributions from spin-flip and non-spin-flip are separately analyzed. It has been found that for certain range of parameters deviations in the normalized magnetoresistance as high as 20% may be achieved. In addition, it has been shown that the spin-flip process is dependent on the wall thickness. - Highlights: • We identify thickness regions within which transport across the wall is dominated by either spin-flip or non-spin-flip process. • We analyze the dependence of the magnetoresistance on both the material's band filling and strength of the exchange interaction. • We identify parameter ranges within which magnetoresistance ratios as high as 20% or even more might be achieved

Roll Attitude Determination of Spin Projectile Based on GPS and Magnetoresistive Sensor

Directory of Open Access Journals (Sweden)

Dandan Yuan

2017-01-01

Full Text Available Improvement in attack accuracy of the spin projectiles is a very significant objective, which increases the overall combat efficiency of projectiles. The accurate determination of the projectile roll attitude is the recent objective of the efficient guidance and control. The roll measurement system for the spin projectile is commonly based on the magnetoresistive sensor. It is well known that the magnetoresistive sensor produces a sinusoidally oscillating signal whose frequency slowly decays with time, besides the possibility of blind spot. On the other hand, absolute sensors such as GPS have fixed errors even though the update rates are generally low. To earn the benefit while eliminating weaknesses from both types of sensors, a mathematical model using filtering technique can be designed to integrate the magnetoresistive sensor and GPS measurements. In this paper, a mathematical model is developed to integrate the magnetoresistive sensor and GPS measurements in order to get an accurate prediction of projectile roll attitude in a real flight time. The proposed model is verified using numerical simulations, which illustrated that the accuracy of the roll attitude measurement is improved.

Domain wall magnetoresistance in nanowires: Dependence on geometrical factors and material parameters

Energy Technology Data Exchange (ETDEWEB)

Allende, S.; Retamal, J.C. [Departamento de Física, CEDENNA, Universidad de Santiago de Chile, USACH, Avenida Ecuador 3493, 917-0124 Santiago (Chile); Altbir, D., E-mail: dora.altbir@usach.cl [Departamento de Física, CEDENNA, Universidad de Santiago de Chile, USACH, Avenida Ecuador 3493, 917-0124 Santiago (Chile); D' Albuquerque e Castro, J. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro 21941-972 (Brazil)

2014-04-15

The magnetoresistance associated with the presence of domain walls in metallic nanowires is investigated as a function of geometrical parameters, corresponding to the wall thickness and the nanowire width, as well as of material parameters, such as the band filling and the exchange interaction. Transport across the structure is described within Landauer formalism. Both cases of saturated and non-saturated ferromagnets are considered, and in all of them the contributions from spin-flip and non-spin-flip are separately analyzed. It has been found that for certain range of parameters deviations in the normalized magnetoresistance as high as 20% may be achieved. In addition, it has been shown that the spin-flip process is dependent on the wall thickness. - Highlights: • We identify thickness regions within which transport across the wall is dominated by either spin-flip or non-spin-flip process. • We analyze the dependence of the magnetoresistance on both the material's band filling and strength of the exchange interaction. • We identify parameter ranges within which magnetoresistance ratios as high as 20% or even more might be achieved.

Drastic Pressure Effect on the Extremely Large Magnetoresistance in WTe2: Quantum Oscillation Study.

Science.gov (United States)

Cai, P L; Hu, J; He, L P; Pan, J; Hong, X C; Zhang, Z; Zhang, J; Wei, J; Mao, Z Q; Li, S Y

2015-07-31

The quantum oscillations of the magnetoresistance under ambient and high pressure have been studied for WTe2 single crystals, in which extremely large magnetoresistance was discovered recently. By analyzing the Shubnikov-de Haas oscillations, four Fermi surfaces are identified, and two of them are found to persist to high pressure. The sizes of these two pockets are comparable, but show increasing difference with pressure. At 0.3 K and in 14.5 T, the magnetoresistance decreases drastically from 1.25×10(5)% under ambient pressure to 7.47×10(3)% under 23.6 kbar, which is likely caused by the relative change of Fermi surfaces. These results support the scenario that the perfect balance between the electron and hole populations is the origin of the extremely large magnetoresistance in WTe2.

Hysteresis as an Implicit Prior in Tactile Spatial Decision Making

Science.gov (United States)

Thiel, Sabrina D.; Bitzer, Sebastian; Nierhaus, Till; Kalberlah, Christian; Preusser, Sven; Neumann, Jane; Nikulin, Vadim V.; van der Meer, Elke; Villringer, Arno; Pleger, Burkhard

2014-01-01

Perceptual decisions not only depend on the incoming information from sensory systems but constitute a combination of current sensory evidence and internally accumulated information from past encounters. Although recent evidence emphasizes the fundamental role of prior knowledge for perceptual decision making, only few studies have quantified the relevance of such priors on perceptual decisions and examined their interplay with other decision-relevant factors, such as the stimulus properties. In the present study we asked whether hysteresis, describing the stability of a percept despite a change in stimulus property and known to occur at perceptual thresholds, also acts as a form of an implicit prior in tactile spatial decision making, supporting the stability of a decision across successively presented random stimuli (i.e., decision hysteresis). We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide ‘same’ rather than ‘different’ on successively presented pin distances. In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants’ decisions than hysteresis. However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance. Furthermore, the less variance was explained by the pin distance on a given decision, the more variance was explained by hysteresis, and vice versa. Our findings suggest that hysteresis acts as an implicit prior in tactile spatial decision making that becomes increasingly important when explicit stimulus properties provide decreasing evidence. PMID:24587045

Equivalent Circuit Modeling of Hysteresis Motors

Energy Technology Data Exchange (ETDEWEB)

Nitao, J J; Scharlemann, E T; Kirkendall, B A

2009-08-31

We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.

Magnetoresistance effect in perovskite-like RCu3Mn4O12 (R - rare earth ion, Th)

International Nuclear Information System (INIS)

Lobanovskij, L.S.; Troyanchuk, I.O.; Trukhanov, S.V.; Pastushonok, S.N.; Pavlov, V.I.

2003-01-01

The study on the electric properties and magnetoresistance effect in the RCu 3 Mn 4 O 12 (where R is the rare-earth ion, Th) is carried out. It is established that all the compositions of the given series demonstrate the magnetoresistive effect, the value whereof at the liquid nitrogen temperature reaches 20% in the field 0.9 T. The increase in the magnetoresistance with the temperature decrease and high sensitivity to the weak magnetic fields at low temperatures indicate that this effect is intergranular. The peak of the magnetoresistance is identified near the Curie temperature (T C ). It is supposed that the degree of the magnetoresistance near the temperature of the magnetic ordering depends on the conditions of the samples synthesis and the effect of the intergranular interlayer on the transport properties of these compositions [ru

Magnetoresistance of Mn-decorated topological line defects in graphene

KAUST Repository

Obodo, Tobechukwu Joshua

2015-01-13

We study the spin polarized transport through Mn-decorated 8-5-5-8 topological line defects in graphene using the nonequilibrium Green\\'s function formalism. Strong preferential bonding overcomes the high mobility of transition metal atoms on graphene and results in stable structures. Despite a large distance between the magnetic centers, we find a high magnetoresistance and attribute this unexpected property to very strong induced π magnetism, in particular for full coverage of all octagonal hollow sites by Mn atoms. In contrast to the magnetoresistance of graphene nanoribbon edges, the proposed system is well controlled and therefore suitable for applications.

Single nucleotide polymorphism (SNP) detection on a magnetoresistive sensor

DEFF Research Database (Denmark)

Rizzi, Giovanni; Østerberg, Frederik Westergaard; Dufva, Martin

2013-01-01

We present a magnetoresistive sensor platform for hybridization assays and demonstrate its applicability on single nucleotide polymorphism (SNP) genotyping. The sensor relies on anisotropic magnetoresistance in a new geometry with a local negative reference and uses the magnetic field from...... the sensor bias current to magnetize magnetic beads in the vicinity of the sensor. The method allows for real-time measurements of the specific bead binding to the sensor surface during DNA hybridization and washing. Compared to other magnetic biosensing platforms, our approach eliminates the need...... for external electromagnets and thus allows for miniaturization of the sensor platform....

Magnetoresistance of Mn-decorated topological line defects in graphene

KAUST Repository

Obodo, Tobechukwu Joshua; Kahaly, M. Upadhyay; Schwingenschlö gl, Udo

2015-01-01

We study the spin polarized transport through Mn-decorated 8-5-5-8 topological line defects in graphene using the nonequilibrium Green's function formalism. Strong preferential bonding overcomes the high mobility of transition metal atoms on graphene and results in stable structures. Despite a large distance between the magnetic centers, we find a high magnetoresistance and attribute this unexpected property to very strong induced π magnetism, in particular for full coverage of all octagonal hollow sites by Mn atoms. In contrast to the magnetoresistance of graphene nanoribbon edges, the proposed system is well controlled and therefore suitable for applications.

Enhanced Magnetoresistance in Molecular Junctions by Geometrical Optimization of Spin-Selective Orbital Hybridization.

Science.gov (United States)

Rakhmilevitch, David; Sarkar, Soumyajit; Bitton, Ora; Kronik, Leeor; Tal, Oren

2016-03-09

Molecular junctions based on ferromagnetic electrodes allow the study of electronic spin transport near the limit of spintronics miniaturization. However, these junctions reveal moderate magnetoresistance that is sensitive to the orbital structure at their ferromagnet-molecule interfaces. The key structural parameters that should be controlled in order to gain high magnetoresistance have not been established, despite their importance for efficient manipulation of spin transport at the nanoscale. Here, we show that single-molecule junctions based on nickel electrodes and benzene molecules can yield a significant anisotropic magnetoresistance of up to ∼200% near the conductance quantum G0. The measured magnetoresistance is mechanically tuned by changing the distance between the electrodes, revealing a nonmonotonic response to junction elongation. These findings are ascribed with the aid of first-principles calculations to variations in the metal-molecule orientation that can be adjusted to obtain highly spin-selective orbital hybridization. Our results demonstrate the important role of geometrical considerations in determining the spin transport properties of metal-molecule interfaces.

Unidirectional spin-Hall and Rashba-Edelstein magnetoresistance in topological insulator-ferromagnet layer heterostructures.

Science.gov (United States)

Lv, Yang; Kally, James; Zhang, Delin; Lee, Joon Sue; Jamali, Mahdi; Samarth, Nitin; Wang, Jian-Ping

2018-01-09

The large spin-orbit coupling in topological insulators results in helical spin-textured Dirac surface states that are attractive for topological spintronics. These states generate an efficient spin-orbit torque on proximal magnetic moments. However, memory or logic spin devices based upon such switching require a non-optimal three-terminal geometry, with two terminals for the writing current and one for reading the state of the device. An alternative two-terminal device geometry is now possible by exploiting the recent discovery of the unidirectional spin Hall magnetoresistance in heavy metal/ferromagnet bilayers and unidirectional magnetoresistance in magnetic topological insulators. Here, we report the observation of such unidirectional magnetoresistance in a technologically relevant device geometry that combines a topological insulator with a conventional ferromagnetic metal. Our devices show a figure of merit (magnetoresistance per current density per total resistance) that is more than twice as large as the highest reported values in all-metal Ta/Co bilayers.

Suppression of Magnetoresistance in Thin WTe2 Flakes by Surface Oxidation.

Science.gov (United States)

Woods, John M; Shen, Jie; Kumaravadivel, Piranavan; Pang, Yuan; Xie, Yujun; Pan, Grace A; Li, Min; Altman, Eric I; Lu, Li; Cha, Judy J

2017-07-12

Recent renewed interest in layered transition metal dichalcogenides stems from the exotic electronic phases predicted and observed in the single- and few-layer limit. Realizing these electronic phases requires preserving the desired transport properties down to a monolayer, which is challenging. Surface oxides are known to impart Fermi level pinning or degrade the mobility on a number of different systems, including transition metal dichalcogenides and black phosphorus. Semimetallic WTe 2 exhibits large magnetoresistance due to electron-hole compensation; thus, Fermi level pinning in thin WTe 2 flakes could break the electron-hole balance and suppress the large magnetoresistance. We show that WTe 2 develops an ∼2 nm thick amorphous surface oxide, which shifts the Fermi level by ∼300 meV at the WTe 2 surface. We also observe a dramatic suppression of the magnetoresistance for thin flakes. However, due to the semimetallic nature of WTe 2 , the effects of Fermi level pinning are well screened and are not the dominant cause for the suppression of magnetoresistance, supported by fitting a two-band model to the transport data, which showed the electron and hole carrier densities are balanced down to ∼13 nm. However, the fitting shows a significant decrease of the mobilities of both electrons and holes. We attribute this to the disorder introduced by the amorphous surface oxide layer. Thus, the decrease of mobility is the dominant factor in the suppression of magnetoresistance for thin WTe 2 flakes. Our study highlights the critical need to investigate often unanticipated and sometimes unavoidable extrinsic surface effects on the transport properties of layered dichalcogenides and other 2D materials.

Tunneling magnetoresistance sensor with pT level 1/f magnetic noise

Science.gov (United States)

Deak, James G.; Zhou, Zhimin; Shen, Weifeng

2017-05-01

Magnetoresistive devices are important components in a large number of commercial electronic products in a wide range of applications including industrial position sensors, automotive sensors, hard disk read heads, cell phone compasses, and solid state memories. These devices are commonly based on anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR), but over the past few years tunneling magnetoresistance (TMR) has been emerging in more applications. Here we focus on recent work that has enabled the development of TMR magnetic field sensors with 1/f noise of less than 100 pT/rtHz at 1 Hz. Of the commercially available sensors, the lowest noise devices have typically been AMR, but they generally have the largest die size. Based on this observation and modeling of experimental data size and geometry dependence, we find that there is an optimal design rule that produces minimum 1/f noise. This design rule requires maximizing the areal coverage of an on-chip flux concentrator, providing it with a minimum possible total gap width, and tightly packing the gaps with MTJ elements, which increases the effective volume and decreases the saturation field of the MTJ freelayers. When properly optimized using this rule, these sensors have noise below 60 pT/rtHz, and could possibly replace fluxgate magnetometers in some applications.

Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry

Science.gov (United States)

Alekseev, P. S.; Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Narozhny, B. N.; Titov, M.

2018-02-01

Ultrapure conductors may exhibit hydrodynamic transport where the collective motion of charge carriers resembles the flow of a viscous fluid. In a confined geometry (e.g., in ultra-high-quality nanostructures), the electronic fluid assumes a Poiseuille-type flow. Applying an external magnetic field tends to diminish viscous effects leading to large negative magnetoresistance. In two-component systems near charge neutrality, the hydrodynamic flow of charge carriers is strongly affected by the mutual friction between the two constituents. At low fields, the magnetoresistance is negative, however, at high fields the interplay between electron-hole scattering, recombination, and viscosity results in a dramatic change of the flow profile: the magnetoresistance changes its sign and eventually becomes linear in very high fields. This nonmonotonic magnetoresistance can be used as a fingerprint to detect viscous flow in two-component conducting systems.

Feedforward hysteresis compensation in trajectory control of piezoelectrically-driven nanostagers

Science.gov (United States)

Bashash, Saeid; Jalili, Nader

2006-03-01

Complex structural nonlinearities of piezoelectric materials drastically degrade their performance in variety of micro- and nano-positioning applications. From the precision positioning and control perspective, the multi-path time-history dependent hysteresis phenomenon is the most concerned nonlinearity in piezoelectric actuators to be analyzed. To realize the underlying physics of this phenomenon and to develop an efficient compensation strategy, the intelligent properties of hysteresis with the effects of non-local memories are discussed. Through performing a set of experiments on a piezoelectrically-driven nanostager with high resolution capacitive position sensor, it is shown that for the precise prediction of hysteresis path, certain memory units are required to store the previous hysteresis trajectory data. Based on the experimental observations, a constitutive memory-based mathematical modeling framework is developed and trained for the precise prediction of hysteresis path for arbitrarily assigned input profiles. Using the inverse hysteresis model, a feedforward control strategy is then developed and implemented on the nanostager to compensate for the system everpresent nonlinearity. Experimental results demonstrate that the controller remarkably eliminates the nonlinear effect if memory units are sufficiently chosen for the inverse model.

Oscillating Magnetoresistance in Graphene p-n Junctions at Intermediate Magnetic Fields.

Science.gov (United States)

Overweg, Hiske; Eggimann, Hannah; Liu, Ming-Hao; Varlet, Anastasia; Eich, Marius; Simonet, Pauline; Lee, Yongjin; Watanabe, Kenji; Taniguchi, Takashi; Richter, Klaus; Fal'ko, Vladimir I; Ensslin, Klaus; Ihn, Thomas

2017-05-10

We report on the observation of magnetoresistance oscillations in graphene p-n junctions. The oscillations have been observed for six samples, consisting of single-layer and bilayer graphene, and persist up to temperatures of 30 K, where standard Shubnikov-de Haas oscillations are no longer discernible. The oscillatory magnetoresistance can be reproduced by tight-binding simulations. We attribute this phenomenon to the modulated densities of states in the n- and p-regions.

Two-dimensional salt and temperature DNA denaturation analysis using a magnetoresistive sensor

DEFF Research Database (Denmark)

Rizzi, Giovanni; Dufva, Martin; Hansen, Mikkel Fougt

2017-01-01

We present a microfluidic system and its use to measure DNA denaturation curves by varying the temperature or salt (Na+) concentration. The readout is based on real-time measurements of DNA hybridization using magnetoresistive sensors and magnetic nanoparticles (MNPs) as labels. We report the first...... melting curves of DNA hybrids measured as a function of continuously decreasing salt concentration at fixed temperature and compare them to the corresponding curves obtained vs. temperature at fixed salt concentration. The magnetoresistive sensor platform provided reliable results under varying....... The results demonstrate that concentration melting provides an attractive alternative to temperature melting in on-chip DNA denaturation experiments and further show that the magnetoresistive platform is attractive due to its low cross-sensitivity to temperature and liquid composition....

Strain driven anisotropic magnetoresistance in antiferromagnetic La$_{0.4}$Sr$_{0.6}$MnO$_{3}$

OpenAIRE

Wong, A. T.; Beekman, C.; Guo, H.; Siemons, W.; Gai, Z.; Arenholz, E.; Takamura, Y.; Ward, T. Z.

2014-01-01

We investigate the effects of strain on antiferromagnetic (AFM) single crystal thin films of La 1-x Sr x MnO 3 (x = 0.6). Nominally unstrained samples have strong magnetoresistance with anisotropic magnetoresistances (AMR) of up to 8%. Compressive strain suppresses magnetoresistance but generates AMR values of up to 63%. Tensile strain presents the only case of a metal-insulator transition and demonstrates a previously unreported AMR behavior. In all three cases, we find evidence of magnetic...

Peculiarities of magnetoresistance in InSb whiskers at cryogenic temperatures

Energy Technology Data Exchange (ETDEWEB)

Druzhinin, A., E-mail: druzh@polynet.lviv.ua [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland); Ostrovskii, I.; Khoverko, Yu. [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland); Liakh-Kaguy, N.; Khytruk, I. [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); Rogacki, K. [International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland)

2015-12-15

Highlights: • Magnetoresistance in InSb whiskers with impurity concentration near MIT is studied. • SdH oscillations of transverse and longitudinal magnetoresistance are examined. • Mechanisms of electron scattering are determined • Main crystal parameters of InSb whiskers are determined. - Abstract: The study of the magnetoresistance in InSb whiskers with an impurity concentration in the vicinity to the metal-insulator phase transition, at low temperature range 4.2–77 K, and in fields, with induction up to 14 T, was conducted. The presence of Shubnikov-de Haas oscillations in both transverse and longitudinal magnetoresistance was observed. The following parameters of InSb whiskers were defined: period of oscillations 0.1 T{sup −1}, cyclotron effective mass of electrons m{sub c} ≈ 0.14m{sub o,} concentration of charge carriers 2.3 × 10{sup 17} cm{sup −3}, g-factor g{sup *} ≈ 30 and Dingle temperature T{sub D} = 14.5 K. To determine the nature of crystal defects, the electron scattering processes on the short-range potential, caused by interaction with polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain centers and ionized impurities in n-InSb whiskers, with defect concentration 2.9 × 10{sup 17} cm{sup −3}, are considered. The temperature dependences of electron mobility in the range 4.2–500 K were calculated.

An efficient hysteresis modeling methodology and its implementation in field computation applications

Energy Technology Data Exchange (ETDEWEB)

Adly, A.A., E-mail: adlyamr@gmail.com [Electrical Power and Machines Dept., Faculty of Engineering, Cairo University, Giza 12613 (Egypt); Abd-El-Hafiz, S.K. [Engineering Mathematics Department, Faculty of Engineering, Cairo University, Giza 12613 (Egypt)

2017-07-15

Highlights: • An approach to simulate hysteresis while taking shape anisotropy into consideration. • Utilizing the ensemble of triangular sub-regions hysteresis models in field computation. • A novel tool capable of carrying out field computation while keeping track of hysteresis losses. • The approach may be extended for 3D tetra-hedra sub-volumes. - Abstract: Field computation in media exhibiting hysteresis is crucial to a variety of applications such as magnetic recording processes and accurate determination of core losses in power devices. Recently, Hopfield neural networks (HNN) have been successfully configured to construct scalar and vector hysteresis models. This paper presents an efficient hysteresis modeling methodology and its implementation in field computation applications. The methodology is based on the application of the integral equation approach on discretized triangular magnetic sub-regions. Within every triangular sub-region, hysteresis properties are realized using a 3-node HNN. Details of the approach and sample computation results are given in the paper.

Magnetoresistance anomalies in ultra-thin granular YBa2Cu3O7−δ bridges

International Nuclear Information System (INIS)

Levi, D.; Shaulov, A.; Koren, G.; Yeshurun, Y.

2013-01-01

Highlights: •Negative magnetoresistance slope in the Tesla regime is observed at low temperatures. •Phase slips explains the observed magnetoresistance at high temperatures. •Quasiparticles tunneling explains the negative slope. -- Abstract: We report on magnetoresistance measurements in 10 nm thick and submicron-wide granular YBa 2 Cu 3 O 7−δ bridges. The results show a strong dependence of the resistance on the magnetic field at low fields crossing over to a relatively weak field dependence at high fields. The field derivative of the resistance at high fields decreases as the temperature is lowered and eventually changes sign, exhibiting a negative slope in a wide field range in the Tesla regime. This negative slope is sensitive to the bias current, turning to be positive as the bias current increases. This complex magnetoresistance behavior is attributed to both phase slips in a distribution of strongly and weakly linked superconducting grains, and tunneling of quasiparticles between grains. The latter dominates at low temperatures and high fields, giving rise to the negative magnetoresistance slope

Corrections for hysteresis curves for rare earth magnet materials measured by open magnetic circuit methods

International Nuclear Information System (INIS)

Nakagawa, Yasuaki

1996-01-01

The methods for testing permanent magnets stipulated in the usual industrial standards are so-called closed magnetic circuit methods which employ a loop tracer using an iron-core electromagnet. If the coercivity exceeds the highest magnetic field generated by the electromagnet, full hysteresis curves cannot be obtained. In the present work, magnetic fields up to 15 T were generated by a high-power water-cooled magnet, and the magnetization was measured by an induction method with an open magnetic circuit, in which the effect of a demagnetizing field should be taken into account. Various rare earth magnets materials such as sintered or bonded Sm-Co and Nd-Fe-B were provided by a number of manufacturers. Hysteresis curves for cylindrical samples with 10 nm in diameter and 2 mm, 3.5 mm, 5 mm, 14 mm or 28 mm in length were measured. Correction for the demagnetizing field is rather difficult because of its non-uniformity. Roughly speaking, a mean demagnetizing factor for soft magnetic materials can be used for the correction, although the application of this factor to hard magnetic material is hardly justified. Thus the dimensions of the sample should be specified when the data obtained by the open magnetic circuit method are used as industrial standards. (author)

Adaptive Hysteresis Band Current Control for Transformerless Single-Phase PV Inverters

DEFF Research Database (Denmark)

Vázquez, Gerardo; Rodriguez, Pedro; Ordoñez, Rafael

2009-01-01

Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response......, and requires a simple implementation in standard digital signal platforms. On the other hand, the main drawback of classical hysteresis current control lies in the fact that the switching frequency is variable, as the hysteresis band is fixed. In this paper a variable band hysteresis control algorithm...... different single-phase PV inverter topologies, by means of simulations performed with PSIM. In addition, the behavior of the thermal losses when using each control structure in such converters has been studied as well....

A new class of Preisach-type isotropic vector model of hysteresis

Energy Technology Data Exchange (ETDEWEB)

Serpico, C.; D' Aquino, M.; Visone, C.; Davino, D

2004-01-01

A new class of scalar hysteresis operators is obtained from the classical Preisach scalar model of hysteresis by introducing a transformation of variables dependent on a suitable function g. The operators of this class are defined by means of a new type of Play operator and are characterized by the property of having the same scalar input-output relationship. These operators are then extended to the isotropic vector case by using the appropriate vector extension of the scalar Play operators. It is shown that the function g, which does not affect the scalar input-output relationship, does affect the vector hysteresis curves. The influence of the function g on vector hysteresis is illustrated by reporting numerically computed rotational hysteresis losses curves.

A BiCMOS Binary Hysteresis Chaos Generator

Science.gov (United States)

Ahmadi, S.; Newcomb, R. W.

A previous op-amp RC circuit which was proven to give chaotic signals is converted to a BiCMOS design more suitable to integrated circuit realization. The structure results from a degree two differential equation which includes binary hysteresis as its nonlinearity. The circuit is realized by differential (voltage to current) pairs feeding two capacitors, which carry the dynamics, with the key component being a (voltage to current) binary hysteresis circuit due to Linares.

Negative magnetoresistance in Dirac semimetal Cd3As2.

Science.gov (United States)

Li, Hui; He, Hongtao; Lu, Hai-Zhou; Zhang, Huachen; Liu, Hongchao; Ma, Rong; Fan, Zhiyong; Shen, Shun-Qing; Wang, Jiannong

2016-01-08

A large negative magnetoresistance (NMR) is anticipated in topological semimetals in parallel magnetic fields, demonstrating the chiral anomaly, a long-sought high-energy-physics effect, in solid-state systems. Recent experiments reveal that the Dirac semimetal Cd3As2 has the record-high mobility and positive linear magnetoresistance in perpendicular magnetic fields. However, the NMR has not yet been unveiled. Here we report the observation of NMR in Cd3As2 microribbons in parallel magnetic fields up to 66% at 50 K and visible at room temperatures. The NMR is sensitive to the angle between magnetic and electrical fields, robust against temperature and dependent on the carrier density. The large NMR results from low carrier densities in our Cd3As2 samples, ranging from 3.0 × 10(17) cm(-3) at 300 K to 2.2 × 10(16) cm(-3) below 50 K. We therefore attribute the observed NMR to the chiral anomaly. In perpendicular magnetic fields, a positive linear magnetoresistance up to 1,670% at 14 T and 2 K is also observed.

Magnetoresistance of samarium in the 4.2-300 K range

International Nuclear Information System (INIS)

Trubitsyn, V.A.; Shalashov, V.F.

1980-01-01

Electric conductivity, transverse and longitudinal magnetoresistance of polycrystalline samarium with the purity of 99.9% in the 4.2-300 K temperature range and in magnetic fields up to 50 ke, are measured. The constituent of specific electric conductivity caused by spin disorder is 30.7 μOhmxcm, m*/m=2.6, the exchange parameter is G=3.1 eVxA 3 . Both transverse and longitudinal magnetoresistance are positive at 4.2 K; and the increase of temperature reveals a number of anomalies, evidently conditioned by the alteration of samarium magnetic structure

Neural networks based identification and compensation of rate-dependent hysteresis in piezoelectric actuators

International Nuclear Information System (INIS)

Zhang, Xinliang; Tan, Yonghong; Su, Miyong; Xie, Yangqiu

2010-01-01

This paper presents a method of the identification for the rate-dependent hysteresis in the piezoelectric actuator (PEA) by use of neural networks. In this method, a special hysteretic operator is constructed from the Prandtl-Ishlinskii (PI) model to extract the changing tendency of the static hysteresis. Then, an expanded input space is constructed by introducing the proposed hysteretic operator to transform the multi-valued mapping of the hysteresis into a one-to-one mapping. Thus, a feedforward neural network is applied to the approximation of the rate-independent hysteresis on the constructed expanded input space. Moreover, in order to describe the rate-dependent performance of the hysteresis, a special hybrid model, which is constructed by a linear auto-regressive exogenous input (ARX) sub-model preceded with the previously obtained neural network based rate-independent hysteresis sub-model, is proposed. For the compensation of the effect of the hysteresis in PEA, the PID feedback controller with a feedforward hysteresis compensator is developed for the tracking control of the PEA. Thus, a corresponding inverse model based on the proposed modeling method is developed for the feedforward hysteresis compensator. Finally, both simulations and experimental results on piezoelectric actuator are presented to verify the effectiveness of the proposed approach for the rate-dependent hysteresis.

Thin-film magnetoresistive absolute position detector

NARCIS (Netherlands)

Groenland, J.P.J.

1990-01-01

The subject of this thesis is the investigation of a digital absolute posi- tion-detection system, which is based on a position-information carrier (i.e. a magnetic tape) with one single code track on the one hand, and an array of magnetoresistive sensors for the detection of the information on the

Enhanced temperature-independent magnetoresistance below the ...

Indian Academy of Sciences (India)

The film exhibits a large nearly temperature-independent magnetoresistance around 99% in the temperature regime below p. The zero field-cooled (ZFC) and field-cooled (FC) magnetization data at 50 Oe shows irreversibility between the ZFC and FC close to the ferromagnetic transition temperature c = 250 K. The ZFC ...

Titration and hysteresis in epigenetic chromatin silencing

International Nuclear Information System (INIS)

Dayarian, Adel; Sengupta, Anirvan M

2013-01-01

Epigenetic mechanisms of silencing via heritable chromatin modifications play a major role in gene regulation and cell fate specification. We consider a model of epigenetic chromatin silencing in budding yeast and study the bifurcation diagram and characterize the bistable and the monostable regimes. The main focus of this paper is to examine how the perturbations altering the activity of histone modifying enzymes affect the epigenetic states. We analyze the implications of having the total number of silencing proteins, given by the sum of proteins bound to the nucleosomes and the ones available in the ambient, to be constant. This constraint couples different regions of chromatin through the shared reservoir of ambient silencing proteins. We show that the response of the system to perturbations depends dramatically on the titration effect caused by the above constraint. In particular, for a certain range of overall abundance of silencing proteins, the hysteresis loop changes qualitatively with certain jump replaced by continuous merger of different states. In addition, we find a nonmonotonic dependence of gene expression on the rate of histone deacetylation activity of Sir2. We discuss how these qualitative predictions of our model could be compared with experimental studies of the yeast system under anti-silencing drugs. (paper)

Detection of magnetic resonance signals using a magnetoresistive sensor

Science.gov (United States)

Budker, Dmitry; Pines, Alexander; Xu, Shoujun; Hilty, Christian; Ledbetter, Micah P; Bouchard, Louis S

2013-10-01

A method and apparatus are described wherein a micro sample of a fluidic material may be assayed without sample contamination using NMR techniques, in combination with magnetoresistive sensors. The fluidic material to be assayed is first subject to pre-polarization, in one embodiment, by passage through a magnetic field. The magnetization of the fluidic material is then subject to an encoding process, in one embodiment an rf-induced inversion by passage through an adiabatic fast-passage module. Thereafter, the changes in magnetization are detected by a pair of solid-state magnetoresistive sensors arranged in gradiometer mode. Miniaturization is afforded by the close spacing of the various modules.

Magnetoresistance of microstructured permalloy ellipses having multi-domain configurations

International Nuclear Information System (INIS)

Kuo, C.Y.; Chung, W.S.; Wu, J.C.; Horng, Lance; Wei, Z.-H.; Lai, M.-F.; Chang, C.-R.

2007-01-01

Mirostructured permalloy ellipses having purposely designed multi-domain configurations were investigated. The samples were fabricated using e-beam lithography through a lift-off process. The magnetoresistance measurements were carried out with a constant dc sensing current under the external magnetic field applied along the short axis. The magnetoresistance curves manifest characteristic features in accordance with the specific domain configurations. Step-like/kink features were observed on the ellipses with cross-tie wall/two-vortex configuration and step-like plus kink magnetorsistance curve was found on the ellipse with cross-tie wall combining with two-vortex structure. A magnetic force microscopy and a micromagnetic simulation were employed to support these results

Anomalous rf magnetoresistance in copper at 4/degree/K

International Nuclear Information System (INIS)

Halama, H.J.; Prodell, A.G.; Rogers, J.T.

1988-03-01

We have measured the effect of a magnetic field on the surface resistance of polycrystalline Cu at f = 1.2 GHz and at 4.4/degree/K; under these conditions the surface resistance is well into the anomalous skin effect regime but has not reached its limiting value. We find that the transverse and longitudinal magnetoresistance are an order of magnitude smaller than the DC magnetoresistance and depend quadratically on the field. At low fields we observe a decrease in surface resistance with increasing field which can be interpreted as a size effect of the TF surface current. 17 refs., 4 figs., 1 tab

Simple Program to Investigate Hysteresis Damping Effect of Cross-Ties on Cables Vibration of Cable-Stayed Bridges

Directory of Open Access Journals (Sweden)

Panagis G. Papadopoulos

2012-01-01

Full Text Available A short computer program, fully documented, is presented, for the step-by-step dynamic analysis of isolated cables or couples of parallel cables of a cable-stayed bridge, connected to each other and possibly with the deck of the bridge, by very thin pretensioned wires (cross-ties and subjected to variation of their axial forces due to traffic or to successive pulses of a wind drag force. A simplified SDOF model, approximating the fundamental vibration mode, is adopted for every individual cable. The geometric nonlinearity of the cables is taken into account by their geometric stiffness, whereas the material nonlinearities of the cross-ties include compressive loosening, tensile yielding, and hysteresis stress-strain loops. Seven numerical experiments are performed. Based on them, it is observed that if two interconnected parallel cables have different dynamic characteristics, for example different lengths, thus different masses, weights, and geometric stiffnesses, too, or if one of them has a small additional mass, then a single pretensioned very thin wire, connecting them to each other and possibly with the deck of the bridge, proves effective in suppressing, by its hysteresis damping, the vibrations of the cables.

Electrical control of memristance and magnetoresistance in oxide magnetic tunnel junctions

KAUST Repository

Zhang, Kun

2015-01-01

Electric-field control of magnetic and transport properties of magnetic tunnel junctions has promising applications in spintronics. Here, we experimentally demonstrate a reversible electrical manipulation of memristance, magnetoresistance, and exchange bias in Co/CoO–ZnO/Co magnetic tunnel junctions, which enables the realization of four nonvolatile resistance states. Moreover, greatly enhanced tunneling magnetoresistance of 68% was observed due to the enhanced spin polarization of the bottom Co/CoO interface. The ab initio calculations further indicate that the spin polarization of the Co/CoO interface is as high as 73% near the Fermi level and plenty of oxygen vacancies can induce metal–insulator transition of the CoO1−v layer. Thus, the electrical manipulation mechanism on the memristance, magnetoresistance and exchange bias can be attributed to the electric-field-driven migration of oxygen ions/vacancies between very thin CoO and ZnO layers.

Giant anisotropic magnetoresistance and planar Hall effect in the Dirac semimetal Cd3As2

Science.gov (United States)

Li, Hui; Wang, Huan-Wen; He, Hongtao; Wang, Jiannong; Shen, Shun-Qing

2018-05-01

Anisotropic magnetoresistance is the change tendency of resistance of a material on the mutual orientation of the electric current and the external magnetic field. Here, we report experimental observations in the Dirac semimetal Cd3As2 of giant anisotropic magnetoresistance and its transverse version, called the planar Hall effect. The relative anisotropic magnetoresistance is negative and up to -68% at 2 K and 10 T. The high anisotropy and the minus sign in this isotropic and nonmagnetic material are attributed to a field-dependent current along the magnetic field, which may be induced by the Berry curvature of the band structure. This observation not only reveals unusual physical phenomena in Weyl and Dirac semimetals, but also finds additional transport signatures of Weyl and Dirac fermions other than negative magnetoresistance.

Robust giant magnetoresistive effect type multilayer sensor

NARCIS (Netherlands)

Lenssen, K.M.H.; Kuiper, A.E.T.; Roozeboom, F.

2002-01-01

A robust Giant Magneto Resistive effect type multilayer sensor comprising a free and a pinned ferromagnetic layer, which can withstand high temperatures and strong magnetic fields as required in automotive applications. The GMR multi-layer has an asymmetric magneto-resistive curve and enables

Hysteresis behaviour of soils and rocks

International Nuclear Information System (INIS)

Hueckel, T.; Nova, R.

1979-01-01

A theory of mechanical hysteresis of geological materials under alternating loading within the yield locus is studied, with emphasis on isotropic pressure sensitivity effects. The hysteresis is described by a 'secant' tensorially linear law which depends on a scalar parameter varying with the advance of the cycle. The constitutive relations are formulated piece-wisely within appropriately conceived stress reversal loci. Specialization to conventional triaxial tests is considered. Finally the feasibility of the model is examined by comparing calculated and actual test data, including those obtained in a cyclic undrained compression test which enlights the phenomenon of cyclic mobility. (orig.)

Anomalous magnetisation process in UFe4Al8 probed by magnetisation and magnetoresistance

International Nuclear Information System (INIS)

Godinho, M.; Estrela, P.; Goncalves, A.P.; Almeida, M.; Spirlet, J.C.; Bonfait, G.

1996-01-01

A strong anisotropic magnetoresistance has been measured in a single crystal of UFe 4 Al 8 and has been used to prove the ferromagnetic order of the U lattice. The giant anomaly detected in the magnetoresistance curves is interpreted as two 90 rotations of the magnetisation. This interpretation has been confirmed by magnetisation measurements. (orig.)

Carnot cycle for magnetic materials: The role of hysteresis

International Nuclear Information System (INIS)

Sasso, Carlo P.; Basso, Vittorio; LoBue, Martino; Bertotti, Giorgio

2006-01-01

The role of hysteresis in a refrigeration thermodynamic cycle involving ferromagnetic materials is discussed. A model allowing to calculate magnetization, entropy and entropy production in systems with hysteresis is used to compute a non-ideal Carnot cycle performed on a ferromagnetic material

Giant magnetoresistance, three-dimensional Fermi surface and origin of resistivity plateau in YSb semimetal.

Science.gov (United States)

Pavlosiuk, Orest; Swatek, Przemysław; Wiśniewski, Piotr

2016-12-09

Very strong magnetoresistance and a resistivity plateau impeding low temperature divergence due to insulating bulk are hallmarks of topological insulators and are also present in topological semimetals where the plateau is induced by magnetic field, when time-reversal symmetry (protecting surface states in topological insulators) is broken. Similar features were observed in a simple rock-salt-structure LaSb, leading to a suggestion of the possible non-trivial topology of 2D states in this compound. We show that its sister compound YSb is also characterized by giant magnetoresistance exceeding one thousand percent and low-temperature plateau of resistivity. We thus performed in-depth analysis of YSb Fermi surface by band calculations, magnetoresistance, and Shubnikov-de Haas effect measurements, which reveals only three-dimensional Fermi sheets. Kohler scaling applied to magnetoresistance data accounts very well for its low-temperature upturn behavior. The field-angle-dependent magnetoresistance demonstrates a 3D-scaling yielding effective mass anisotropy perfectly agreeing with electronic structure and quantum oscillations analysis, thus providing further support for 3D-Fermi surface scenario of magnetotransport, without necessity of invoking topologically non-trivial 2D states. We discuss data implying that analogous field-induced properties of LaSb can also be well understood in the framework of 3D multiband model.

A thermodynamic model of contact angle hysteresis.

Science.gov (United States)

Makkonen, Lasse

2017-08-14

When a three-phase contact line moves along a solid surface, the contact angle no longer corresponds to the static equilibrium angle but is larger when the liquid is advancing and smaller when the liquid is receding. The difference between the advancing and receding contact angles, i.e., the contact angle hysteresis, is of paramount importance in wetting and capillarity. For example, it determines the magnitude of the external force that is required to make a drop slide on a solid surface. Until now, fundamental origin of the contact angle hysteresis has been controversial. Here, this origin is revealed and a quantitative theory is derived. The theory is corroborated by the available experimental data for a large number of solid-liquid combinations. The theory is applied in modelling the contact angle hysteresis on a textured surface, and these results are also in quantitative agreement with the experimental data.

Giant magnetoresistive properties of FexAu100-x alloys produced by mechanical alloying

International Nuclear Information System (INIS)

Socolovsky, L.M.; Sanchez, F.H.; Shingu, P.H.

2001-01-01

The Fe x Au 100- x alloys were produced for the first time by mechanical alloying. Resistance of samples with iron concentrations of x=15, 20, 25, and 30 at% were measured at 77 K under an applied field of 14 kOe. A maximum in magnetoresistive ratio (Δρ/ρ) of 3.5% was obtained for Fe 25 Au 75 . Samples were annealed in order to enhance magnetoresistive properties. These samples exhibit larger ratios, primarily due to the elimination of defects. X-ray diffraction Moessbauer spectroscopy and magnetoresistance measurements were performed, in order to correlate bulk and hyperfine magnetic properties with crystalline structure. X-ray diffractograms show an FCC structure, with no evidence for a BCC one

Large magnetoresistance in (AA')2FeReO6 double perovskites

International Nuclear Information System (INIS)

Teresa, J.M. de; Serrate, D.; Blasco, J.; Ibarra, M.R.; Morellon, L.

2005-01-01

We review the main structural, magnetic and magnetotransport properties of the intriguing (AA') 2 FeReO 6 magnetic double perovskites. As the average cation size decreases, the crystallographic structure at room temperature evolves from cubic [(AA') 2 =Ba 2 , Ba 1.5 Sr 0.5 , BaSr, Ba 0.5 Sr 1.5 ] to tetragonal [(AA') 2 =Sr 2 ] and monoclinic [(AA') 2 =Ca 0.5 Sr 1.5 , CaSr, Ca 1.5 Sr 0.5 , Ca 2 ]. The Curie temperature increases anomalously from ∼303K for Ba 2 to ∼522K for Ca 2 in sharp contrast with the observed behaviour in the isostructural compounds (AA') 2 FeMoO 6 . Other anomalous features in the (AA') 2 FeReO 6 series are: the large magnetic anisotropy, the large magnetoelastic coupling and the semiconducting behaviour of the monoclinic compounds. The monoclinic compounds undergo a structural/magnetic transition at T S below 125K. Three different magnetoresistance mechanisms have been identified: the intergrain negative magnetoresistance effect, which is present across the whole series of compounds, and in the case of the monoclinic compounds below T S a negative magnetoresistance effect associated to the melting of the low-temperature phase and a positive magnetoresistance effect only present in (AA') 2 =Ca 2 below T∼50K

Relating hysteresis and electrochemistry in graphene field effect transistors

NARCIS (Netherlands)

Veligura, Alina; Zomer, Paul J.; Vera-Marun, Ivan J.; Jozsa, Csaba; Gordiichuk, Pavlo I.; van Wees, Bart J.

2011-01-01

Hysteresis and commonly observed p-doping of graphene based field effect transistors (FETs) have been discussed in reports over the last few years. However, the interpretation of experimental works differs; and the mechanism behind the appearance of the hysteresis and the role of charge transfer

Transverse magnetoresistance induced by electron-surface scattering on thin gold films: Experiment and theory

International Nuclear Information System (INIS)

Oyarzún, Simón; Henríquez, Ricardo; Suárez, Marco Antonio; Moraga, Luis; Kremer, Germán; Munoz, Raúl C.

2014-01-01

We report new experimental data regarding the transverse magnetoresistance measured in a family of thin gold films of different thickness with the electric field E oriented perpendicular to the magnetic field B (both fields contained within the plane of the film), as well as a theoretical description of size effects based upon a solution of Boltzmann Transport Equation. The measurements were performed at low temperatures T (4 K ≤ T ≤ 50 K) under magnetic field strengths B (1.5 T ≤ B ≤ 9 T). The magnetoresistance signal can be univocally identified as arising from electron-surface scattering, for the Hall mobility at 4 K depends linearly on film thickness. The magnetoresistance signal exhibits a marked thickness dependence, and its curvature as a function of magnetic field B varies with film thickness. The theoretical description of the magnetic field dependence of the magnetoresistance requires a Hall field that varies with the thickness of the film; this Hall field is tuned to reproduce the experimental data.

Transverse magnetoresistance induced by electron-surface scattering on thin gold films: Experiment and theory

Energy Technology Data Exchange (ETDEWEB)

Oyarzún, Simón [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne CEDEX (France); Henríquez, Ricardo [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Casilla 110-V, Valparaíso (Chile); Suárez, Marco Antonio; Moraga, Luis [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile); Kremer, Germán [Bachillerato, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago 7800024 (Chile); Munoz, Raúl C., E-mail: ramunoz@ing.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449 (Chile)

2014-01-15

We report new experimental data regarding the transverse magnetoresistance measured in a family of thin gold films of different thickness with the electric field E oriented perpendicular to the magnetic field B (both fields contained within the plane of the film), as well as a theoretical description of size effects based upon a solution of Boltzmann Transport Equation. The measurements were performed at low temperatures T (4 K ≤ T ≤ 50 K) under magnetic field strengths B (1.5 T ≤ B ≤ 9 T). The magnetoresistance signal can be univocally identified as arising from electron-surface scattering, for the Hall mobility at 4 K depends linearly on film thickness. The magnetoresistance signal exhibits a marked thickness dependence, and its curvature as a function of magnetic field B varies with film thickness. The theoretical description of the magnetic field dependence of the magnetoresistance requires a Hall field that varies with the thickness of the film; this Hall field is tuned to reproduce the experimental data.

A new Preisach-type vector model of hysteresis

Energy Technology Data Exchange (ETDEWEB)

D' Aquino, M. E-mail: mdaquino@unina.it; Serpico, C. E-mail: serpico@unina.it

2004-05-01

A new class of scalar hysteresis operators is obtained from the classical Preisach scalar model of hysteresis by introducing a transformation of variables dependent on a suitable function g. The operators of this class are defined by means of a new type of Play operator and are characterized by the property of having the same scalar input-output relationship. These operators are then extended to the isotropic vector case by using the vector extension of the scalar Play operator. It is shown that the function g, although does not affect the scalar behavior, it does affect the vector behaviour of the mathematical model. The influence of the function g is illustrated by reporting numerically computed rotational hysteresis losses curves for different choices of the function g.

Negative magnetoresistance of pitch-based carbon fibers Temperature and pressure dependence

Science.gov (United States)

Hambourger, P. D.

1986-01-01

The negative transverse magnetoresistance of high-modulus pitch-based carbon fibers has been measured over the temperature range 1.3-4.2 K at ambient pressure and at 4.2 K under hydrostatic pressure up to 16 kbar. At low fields (less than 0.5 torr) the magnitude of the magnetoresistance increases markedly as the temperature is lowered from 4.2 K to 1.3 K, in disagreement with Bright's theoretical model, and decreases with pressure at the rate -0.6 percent/kbar.

The effect of magnetic ordering on the giant magnetoresistance of Cr-Fe-V and Cr-Fe-Mn

International Nuclear Information System (INIS)

Somsen, Ch.; Acet, M.; Nepecks, G.; Wassermann, E.F.

2000-01-01

Cr-rich Cr 1-x Fe x alloys with compositions in the vicinity of mixed ferromagnetic and antiferromagnetic exchange (x=0.18) exhibit giant magnetoresistance. In order to understand the influence of the antiferromagnetism of Cr on the giant magnetoresistance one can manipulate the antiferromagnetic exchange either by adding vanadium, which destroys the antiferromagnetism of Cr, or by adding manganese, which enhances it. Cr-Fe-V and Cr-Fe-Mn alloys also have Curie temperatures that lie between low temperatures and room temperature in the concentration region where giant magnetoresistance is observed. Therefore, they are also used as samples to study the magnetoresistance as a function of the strength of FM exchange. We discuss these points in the light of temperature and concentration-dependent magnetoresistance experiments on Cr 0.99-x Fe x V 0.01 , Cr 0.96-x Fe x V 0.04 , Cr 0.90-x Fe x Mn 0.10 and Cr 0.55 Fe x Mn 0.45-x alloys. Results indicate that the most favorable condition for a large magnetoresistance in these alloys occurs at temperatures near the Curie temperature

Tuning spin transport properties and molecular magnetoresistance through contact geometry

Science.gov (United States)

Ulman, Kanchan; Narasimhan, Shobhana; Delin, Anna

2014-01-01

Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its "closed" and "open" conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ˜5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ˜400%.

Tuning spin transport properties and molecular magnetoresistance through contact geometry

International Nuclear Information System (INIS)

Ulman, Kanchan; Narasimhan, Shobhana; Delin, Anna

2014-01-01

Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its “closed” and “open” conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%

Tuning spin transport properties and molecular magnetoresistance through contact geometry.

Science.gov (United States)

Ulman, Kanchan; Narasimhan, Shobhana; Delin, Anna

2014-01-28

Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its "closed" and "open" conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%.

Temperature-dependent plastic hysteresis in highly confined polycrystalline Nb films

Science.gov (United States)

Waheed, S.; Hao, R.; Zheng, Z.; Wheeler, J. M.; Michler, J.; Balint, D. S.; Giuliani, F.

2018-02-01

In this study, the effect of temperature on the cyclic deformation behaviour of a confined polycrystalline Nb film is investigated. Micropillars encapsulating a thin niobium interlayer are deformed under cyclic axial compression at different test temperatures. A distinct plastic hysteresis is observed for samples tested at elevated temperatures, whereas negligible plastic hysteresis is observed for samples tested at room temperature. These results are interpreted using planar discrete dislocation plasticity incorporating slip transmission across grain boundaries. The effect of temperature-dependent grain boundary energy and dislocation mobility on dislocation penetration and, consequently, the size of plastic hysteresis is simulated to correlate with the experimental results. It is found that the decrease in grain boundary energy barrier caused by the increase in temperature does not lead to any appreciable change in the cyclic response. However, dislocation mobility significantly affects the size of plastic hysteresis, with high mobilities leading to a larger hysteresis. Therefore, it is postulated that the experimental observations are predominantly caused by an increase in dislocation mobility as the temperature is increased above the critical temperature of body-centred cubic niobium.

Contact angle hysteresis: a review of fundamentals and applications

NARCIS (Netherlands)

Eral, Burak; 't Mannetje, Dieter; Oh, J.M.

2013-01-01

Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate a description of contact angle hysteresis into physical models. To

Magnetic features in REMeO3 perovskites and their solid solutions (RE=rare-earth, Me=Mn, Cr)

International Nuclear Information System (INIS)

Moure, Carlos; Peña, Octavio

2013-01-01

Magnetic hysteresis displacement, thermal inversion of the magnetization, hysteresis loops jumps and crossing branches of hysteresis loops at low magnetic fields are reviewed. Most of these phenomena have been observed in magnetic oxide systems, particularly in perovskite-type manganites and chromites. The paper takes into account structural considerations and different geometrical parameters, such as volume or thin layers. - Highlights: ►Review of both spin reversal phenomena thermal and displacive. ► Study of the crossing branches of the magnetic hysteresis loops. ► Review of the behavior of some stepped hysteresis loops

Magnetic features in REMeO{sub 3} perovskites and their solid solutions (RE=rare-earth, Me=Mn, Cr)

Energy Technology Data Exchange (ETDEWEB)

Moure, Carlos, E-mail: cmoure@icv.csic.es [Instituto de Cerámica y Vidrio, CSIC, Electroceramics Department, Kelsen No. 5, 28049 Cantoblanco, Madrid (Spain); Peña, Octavio [Institut des Sciences Chimiques de Rennes, UMR 6226, Université de Rennes 1, 35042 Rennes (France)

2013-07-15

Magnetic hysteresis displacement, thermal inversion of the magnetization, hysteresis loops jumps and crossing branches of hysteresis loops at low magnetic fields are reviewed. Most of these phenomena have been observed in magnetic oxide systems, particularly in perovskite-type manganites and chromites. The paper takes into account structural considerations and different geometrical parameters, such as volume or thin layers. - Highlights: ►Review of both spin reversal phenomena thermal and displacive. ► Study of the crossing branches of the magnetic hysteresis loops. ► Review of the behavior of some stepped hysteresis loops.

Effect of pressure on the magnetoresistance of single crystal Nd0.5Sr0.36Pb0.14MnO3-δ

International Nuclear Information System (INIS)

Khazeni, K.; Jia, Y.X.; Lu, L.; Crespi, V.H.; Cohen, M.L.; Zettl, A.

1996-01-01

To investigate the observed huge variations in magnetoresistance between different samples of manganite perovskites we have performed the first high-pressure measurement of magnetoresistance in single crystal Nd 0.5 Sr 0.36 Pb 0.14 MnO 3-δ . Both resistivity and magnetoresistance are strongly suppressed upon application of pressure. The decrease in magnetoresistance with increasing pressure rules out substrate-induced compressive strain as a source of enhanced magnetoresistance. Instead, the magnetoresistance differences between samples are ascribed primarily to the more abrupt nature of the semiconductorlike to metallic phase transition at lower temperatures. copyright 1996 The American Physical Society

Anomalous magnetoresistance in the spinel superconductor LiTi2O4.

Science.gov (United States)

Jin, K; He, G; Zhang, X; Maruyama, S; Yasui, S; Suchoski, R; Shin, J; Jiang, Y; Yu, H S; Yuan, J; Shan, L; Kusmartsev, F V; Greene, R L; Takeuchi, I

2015-05-20

LiTi2O4 is a unique compound in that it is the only known spinel oxide superconductor. The lack of high quality single crystals has thus far prevented systematic investigations of its transport properties. Here we report a careful study of transport and tunnelling spectroscopy in epitaxial LiTi2O4 thin films. An unusual magnetoresistance is observed which changes from nearly isotropic negative to prominently anisotropic positive as the temperature is decreased. We present evidence that shows that the negative magnetoresistance likely stems from the suppression of local spin fluctuations or spin-orbit scattering centres. The positive magnetoresistance suggests the presence of an orbital-related state, also supported by the fact that the superconducting energy gap decreases as a quadratic function of magnetic field. These observations indicate that the spin-orbital fluctuations play an important role in LiTi2O4 in a manner similar to high-temperature superconductors.

Research on the Hysteresis Effect on Positioning the System with Flexible Elements

Directory of Open Access Journals (Sweden)

Audrius Čereška

2015-03-01

Full Text Available The paper analyzes the hysteresis phenomenon of positioning systems with flexible elements for transmitting motion of which piezoelectric actuators are used. The article investigates the influence of hysteresis on the accuracy of positioning systems. A special test bench for conducting research and stand-up methodology for carrying out experimental researches have been used. The test bench includes a computer piezo controller, an inductive displacement sensor and a dynamic data collector used for gathering data and transmitting it to the software package. Mathematical modelling of hysteresis using Matlab/Simulink software package has been done. The performed research has shown that the hysteresis model of maximum dispersion error compared to experimental results makes less than 5%. Thus, it can be stated that the selected method for hysteresis modelling is suitable for precision positioning systems having deformable elements and controlled employing piezoelectric actuators to model hysteresis.

Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes

Science.gov (United States)

Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

2015-05-01

Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3- antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

Perovskite–fullerene hybrid materials suppress hysteresis in planar diodes

Science.gov (United States)

Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

2015-01-01

Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite–PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3− antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour. PMID:25953105

Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

KAUST Repository

Xu, Jixian

2015-05-08

Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3(-) antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour.

Strain effects on anisotropic magnetoresistance in a nanowire spin valve

Science.gov (United States)

Hossain, Md I.; Maksud, M.; Subramanian, A.; Atulasimha, J.; Bandyopadhyay, S.

2016-11-01

The longitudinal magnetoresistance of a copper nanowire contacted by two cobalt contacts shows broad spin-valve peaks at room temperature. However, when the contacts are slightly heated, the peaks change into troughs which are signature of anisotropic magnetoresistance (AMR). Under heating, the differential thermal expansion of the contacts and the substrate generates a small strain in the cobalt contacts which enhances the AMR effect sufficiently to change the peak into a trough. This shows the extreme sensitivity of AMR to strain. The change in the AMR resistivity coefficient due to strain is estimated to be a few m Ω -m/microstrain.

Cross Voltage Control with Inner Hysteresis Current Control for Multi-output Boost Converter

DEFF Research Database (Denmark)

Nami, Alireza; Zare, Firuz; Blaabjerg, Frede

2009-01-01

Multi-output boost (MOB) converter is a novel DC-DC converter unlike the regular boost converter, has the ability to share its total output voltage and to have different series output voltage from a given duty cycle for low and high power applications. In this paper, discrete voltage control...... with inner hysteresis current control loop has been proposed to keep the simplicity of the control law for the double-output MOB converter, which can be implemented by a combination of analogue and logical ICs or simple microcontroller to constrain the output voltages of MOB converter at their reference...... voltages against variation in load or input voltage. The salient features of the proposed control strategy are simplicity of implementation and ease to extend to multiple outputs in the MOB converter. Simulation and experimental results are presented to show the validity of control strategy....

Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

International Nuclear Information System (INIS)

Povzner, A.A.; Volkov, A.G.

2017-01-01

Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

Energy Technology Data Exchange (ETDEWEB)

Povzner, A.A., E-mail: a.a.povzner@urfu.ru; Volkov, A.G., E-mail: agvolkov@yandex.ru

2017-06-15

Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

Giant magnetoresistance in lateral metallic nanostructures for spintronic applications.

Science.gov (United States)

Zahnd, G; Vila, L; Pham, V T; Marty, A; Beigné, C; Vergnaud, C; Attané, J P

2017-08-25

In this letter, we discuss the shift observed in spintronics from the current-perpendicular-to-plane geometry towards lateral geometries, illustrating the new opportunities offered by this configuration. Using CoFe-based all-metallic LSVs, we show that giant magnetoresistance variations of more than 10% can be obtained, competitive with the current-perpendicular-to-plane giant magnetoresistance. We then focus on the interest of being able to tailor freely the geometries. On the one hand, by tailoring the non-magnetic parts, we show that it is possible to enhance the spin signal of giant magnetoresistance structures. On the other hand, we show that tailoring the geometry of lateral structures allows creating a multilevel memory with high spin signals, by controlling the coercivity and shape anisotropy of the magnetic parts. Furthermore, we study a new device in which the magnetization direction of a nanodisk can be detected. We thus show that the ability to control the magnetic properties can be used to take advantage of all the spin degrees of freedom, which are usually occulted in current-perpendicular-to-plane devices. This flexibility of lateral structures relatively to current-perpendicular-to-plane structures is thus found to offer a new playground for the development of spintronic applications.

Tunneling magnetoresistance dependence on the temperature in a ferromagnetic Zener diode

Energy Technology Data Exchange (ETDEWEB)

Comesana, E; Aldegunde, M; GarcIa-Loureiro, A, E-mail: enrique.comesana@usc.e [Departamento de Electronica e Computacion, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

2009-11-15

In the present work we focus on the study of the temperature dependence of the tunnelling current in a ferromagnetic Zener diode. We predict the tunneling magnetoresistance dependence on the temperature. Large doping concentrations lead to magnetic semiconductors with Curie temperature T{sub C} near or over room temperature and this will facilitate the introduction of new devices that make use of the ferromagnetism effects. According to our calculations the tunneling magnetoresistance has the form TMR {proportional_to} (T{sup n}{sub C}-T{sup n}).

Magnetoresistance in hybrid organic spin valves at the onset of multiple-step tunneling.

Science.gov (United States)

Schoonus, J J H M; Lumens, P G E; Wagemans, W; Kohlhepp, J T; Bobbert, P A; Swagten, H J M; Koopmans, B

2009-10-02

By combining experiments with simple model calculations, we obtain new insight in spin transport through hybrid, CoFeB/Al2O3(1.5 nm)/tris(8-hydroxyquinoline)aluminium (Alq3)/Co spin valves. We have measured the characteristic changes in the I-V behavior as well as the intrinsic loss of magnetoresistance at the onset of multiple-step tunneling. In the regime of multiple-step tunneling, under the condition of low hopping rates, spin precession in the presence of hyperfine coupling is conjectured to be the relevant source of spin relaxation. A quantitative analysis leads to the prediction of a symmetric magnetoresistance around zero magnetic field in addition to the hysteretic magnetoresistance curves, which are indeed observed in our experiments.

Efficient spin injection and giant magnetoresistance in Fe / MoS 2 / Fe junctions

KAUST Repository

Dolui, Kapildeb

2014-07-02

We demonstrate giant magnetoresistance in Fe/MoS2/Fe junctions by means of ab initio transport calculations. We show that junctions incorporating either a monolayer or a bilayer of MoS2 are metallic and that Fe acts as an efficient spin injector into MoS2 with an efficiency of about 45%. This is the result of the strong coupling between the Fe and S atoms at the interface. For junctions of greater thickness, a maximum magnetoresistance of ∼300% is obtained, which remains robust with the applied bias as long as transport is in the tunneling limit. A general recipe for improving the magnetoresistance in spin valves incorporating layered transition metal dichalcogenides is proposed. © 2014 American Physical Society.

OCV Hysteresis in Li-Ion Batteries including Two-Phase Transition Materials

Directory of Open Access Journals (Sweden)

Michael A. Roscher

2011-01-01

Full Text Available The relation between batteries' state of charge (SOC and open-circuit voltage (OCV is a specific feature of electrochemical energy storage devices. Especially NiMH batteries are well known to exhibit OCV hysteresis, and also several kinds of lithium-ion batteries show OCV hysteresis, which can be critical for reliable state estimation issues. Electrode potential hysteresis is known to result from thermodynamical entropic effects, mechanical stress, and microscopic distortions within the active electrode materials which perform a two-phase transition during lithium insertion/extraction. Hence, some Li-ion cells including two-phase transition active materials show pronounced hysteresis referring to their open-circuit voltage. This work points out how macroscopic effects, that is, diffusion limitations, superimpose the latte- mentioned microscopic mechanisms and lead to a shrinkage of OCV hysteresis, if cells are loaded with high current rates. To validate the mentioned interaction, Li-ion cells' state of charge is adjusted to 50% with various current rates, beginning from the fully charged and the discharged state, respectively. As a pronounced difference remains between the OCV after charge and discharge adjustment, obviously the hysteresis vanishes as the target SOC is adjusted with very high current rate.

A Sorption Hysteresis Model For Cellulosic Materials

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Damkilde, Lars

2006-01-01

The equilibrium concentration of adsorbed water in cellulosic materials is dependent on the history of the variations of vapor pressure in the ambient air, i.e. sorption hysteresis. Existing models to describe this phenomenon such as the independent domain theory have numerical drawbacks and....../or imply accounting for the entire history variations of every material point. This paper presents a sorption hysteresis model based on a state formulation and expressed in closed-form solutions, which makes it suitable for implementation into a numerical method....

Universal Approach toward Hysteresis-Free Perovskite Solar Cell via Defect Engineering.

Science.gov (United States)

Son, Dae-Yong; Kim, Seul-Gi; Seo, Ja-Young; Lee, Seon-Hee; Shin, Hyunjung; Lee, Donghwa; Park, Nam-Gyu

2018-01-31

Organic-inorganic halide perovskite is believed to be a potential candidate for high efficiency solar cells because power conversion efficiency (PCE) was certified to be more than 22%. Nevertheless, mismatch of PCE due to current density (J)-voltage (V) hysteresis in perovskite solar cells is an obstacle to overcome. There has been much lively debate on the origin of J-V hysteresis; however, effective methodology to solve the hysteric problem has not been developed. Here we report a universal approach for hysteresis-free perovskite solar cells via defect engineering. A severe hysteresis observed from the normal mesoscopic structure employing TiO 2 and spiro-MeOTAD is almost removed or does not exist upon doping the pure perovskites, CH 3 NH 3 PbI 3 and HC(NH 2 ) 2 PbI 3 , and the mixed cation/anion perovskites, FA 0.85 MA 0.15 PbI 2.55 Br 0.45 and FA 0.85 MA 0.1 Cs 0.05 PbI 2.7 Br 0.3 , with potassium iodide. Substantial reductions in low-frequency capacitance and bulk trap density are measured from the KI-doped perovskite, which is indicative of trap-hysteresis correlation. A series of experiments with alkali metal iodides of LiI, NaI, KI, RbI and CsI reveals that potassium ion is the right element for hysteresis-free perovskite. Theoretical studies suggest that the atomistic origin of the hysteresis of perovskite solar cells is not the migration of iodide vacancy but results from the formation of iodide Frenkel defect. Potassium ion is able to prevent the formation of Frenkel defect since K + energetically prefers the interstitial site. A complete removal of hysteresis is more pronounced at mixed perovskite system as compared to pure perovskites, which is explained by lower formation energy of K interstitial (-0.65 V for CH 3 NH 3 PbI 3 vs -1.17 V for mixed perovskite). The developed KI doping methodology is universally adapted for hysteresis-free perovskite regardless of perovskite composition and device structure.

A study of inelastic electron-phonon interactions on tunneling magnetoresistance of a nano-scale device

International Nuclear Information System (INIS)

Modarresi, M.; Roknabadi, M.R.; Shahtahmasbi, N.; Vahedi Fakhrabad, D.; Arabshahi, H.

2011-01-01

In this research, we have studied the effect of inelastic electron-phonon interactions on current-voltage characteristic and tunneling magnetoresistance of a polythiophene molecule that is sandwiched between two cobalt electrodes using modified Green's function method as proposed by Walczak. The molecule is described with a modified Su-Schrieffer-Heeger Hamiltonian. The ground state of the molecule is obtained by Hellman-Feynman theorem. Electrodes are described in the wide-band approximation and spin-flip is neglected during conduction. Our calculation results show that with increase in voltage the currents increase and tunneling magnetoresistance decreases. Change in tunneling magnetoresistance due to inelastic interactions is limited in a small bias voltage interval and can be neglected in the other bias voltages. -- Research Highlights: →We investigate the effect of inelastic interaction on transport properties. →Due to inelastic interactions tunneling magnetoresistance decreases. →Decrease in TMR is restricted in a small voltage interval.

Superconducting transition and low-field magnetoresistance of a niobium single crystal at 4.2 deg. K; Transition supraconductrice et magnetoresistance en champ faible d'un echantillon monocristallin de niobium a 4.2 deg. K

Energy Technology Data Exchange (ETDEWEB)

Perriot, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires. Service de physique du solide et de resonnance magnetique

1967-01-01

We report the study of the electrical resistance of a niobium single crystal, at 4.2 deg. K, from the beginning of the superconductive transition to 80 kilo oersteds. Critical fieldsH{sub c2} and H{sub c3} have been determined. Influences on superconductive transition of current density, field-current angle, crystal orientation and magnetoresistance have been studied. Variation laws of low-field transverse and longitudinal magneto-resistances have been determined. (author) [French] La variation de la resistance electrique d'un monocristal cylindrique de niobium a ete etudiee, a 4,2 deg. K, depuis le debut de la transition supraconductrice jusqu'a 80 kilooersteds. Les champs critiques H{sub c2} et H{sub c3} ont ete determines. On a etudie l'influence de la densite de courant, de l'angle champ-courant, de l'anisotropie cristalline et de la magnetoresistance sur la transition supraconductrice. Les lois de variation des magnetoresistances transversale et longitudinale ont ete determinees dans le domaine des champs faibles. (auteur)

Assessing temporal variations in connectivity through suspended sediment hysteresis analysis

Science.gov (United States)

Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; Melland, Alice; Mellander, Per-Erik; hUallacháin, Daire Ó.

2016-04-01

Connectivity provides a valuable concept for understanding catchment-scale sediment dynamics. In intensive agricultural catchments, land management through tillage, high livestock densities and extensive land drainage practices significantly change hydromorphological behaviour and alter sediment supply and downstream delivery. Analysis of suspended sediment-discharge hysteresis has offered insights into sediment dynamics but typically on a limited selection of events. Greater availability of continuous high-resolution discharge and turbidity data and qualitative hysteresis metrics enables assessment of sediment dynamics during more events and over time. This paper assesses the utility of this approach to explore seasonal variations in connectivity. Data were collected from three small (c. 10 km2) intensive agricultural catchments in Ireland with contrasting morphologies, soil types, land use patterns and management practices, and are broadly defined as low-permeability supporting grassland, moderate-permeability supporting arable and high-permeability supporting arable. Suspended sediment concentration (using calibrated turbidity measurements) and discharge data were collected at 10-min resolution from each catchment outlet and precipitation data were collected from a weather station within each catchment. Event databases (67-90 events per catchment) collated information on sediment export metrics, hysteresis category (e.g., clockwise, anti-clockwise, no hysteresis), numeric hysteresis index, and potential hydro-meteorological controls on sediment transport including precipitation amount, duration, intensity, stream flow and antecedent soil moisture and rainfall. Statistical analysis of potential controls on sediment export was undertaken using Pearson's correlation coefficient on separate hysteresis categories in each catchment. Sediment hysteresis fluctuations through time were subsequently assessed using the hysteresis index. Results showed the numeric

PREFACE: International Workshop on Multi-Rate Processes and Hysteresis

Science.gov (United States)

Mortell, Michael P.; O'Malley, Robert E.; Pokrovskii, Alexei; Rachinskii, Dmitrii; Sobolev, Vladimir A.

2008-07-01

We are interested in singular perturbation problems and hysteresis as common strongly nonlinear phenomena that occur in many industrial, physical and economic systems. The wording `strongly nonlinear' means that linearization will not encapsulate the observed phenomena. Often these two types of phenomena are manifested for different stages of the same or similar processes. A number of fundamental hysteresis models can be considered as limit cases of time relaxation processes, or admit an approximation by a differential equation which is singular with respect to a particular parameter. However, the amount of interaction between practitioners of theories of systems with time relaxation and systems with hysteresis (and between the `relaxation' and `hysteresis' research communities) is still low, and cross-fertilization is small. In recent years Ireland has become a home for a series of prestigious International Workshops in Singular Perturbations and Hysteresis: International Workshop on Multi-rate Processes and Hysteresis (University College Cork, Ireland, 3-8 April 2006). Proceedings are published in Journal of Physics: Conference Series, volume 55. See further information at http://euclid.ucc.ie/murphys2008.htm International Workshop on Hysteresis and Multi-scale Asymptotics (University College Cork, Ireland, 17-21 March 2004). Proceedings are published in Journal of Physics: Conference Series, volume 22. See further information at http://euclid.ucc.ie/murphys2006.htm International Workshop on Relaxation Oscillations and Hysteresis (University College Cork, Ireland, 1-6 April 2002). The related collection of invited lectures, was published as a volume Singular Perturbations and Hysteresis, SIAM, Philadelphia, 2005. See further information at http://euclid.ucc.ie/hamsa2004.htm International Workshop on Geometrical Methods of Nonlinear Analysis and Semiconductor Laser Dynamics (University College Cork, Ireland, 5-5 April 2001). A collection of invited papers has been

Ac magnetic hysteresis loops of Bi-Sr-Ca-Cu-O 110-K-phase superconductors and the effect of microstructural alteration

International Nuclear Information System (INIS)

Kumar, N.H.; Bai, V.S.

1996-01-01

The field variations of ac M-H loops are recorded at 77 K and 33 Hz using a lock-in flat-band detection method in sintered and press sintered 110-K-phase samples of the Bi-Sr-Ca-Cu-O system. From the slope of the M vs H m curve the flux profiles and the effective relative permeability (μ cer ) of the samples are determined. Using this value of μ cer the intergrain and intragrain contributions to the magnetization are separated out. The intergranular loops of the sintered sample could be simulated very well using Kim close-quote s model, while for the press-sintered sample the exponential model gives a better fit. Our results show that the loop closure exhibited by the intergranular loop can be simulated to the critical state models without subtracting the wing portion in contrast to the Dersch-Blatter approach. The intragranular loops of sintered samples show quite a good fit to the exponential model after introducing the surface barrier modification. The intergranular critical current density (J ci ) and the apparent lower critical field (H c1g ) of the grains are found to be enhanced due to press sintering. The field variations of the various physical quantities obtained from the loops are analyzed to see the effect of microstructural alterations introduced by the press-sintering method. By doing a fast Fourier transform on the M vs t curve the harmonic components are separated out and their variation with the ac field amplitude is studied. copyright 1996 The American Physical Society

A Magnetoresistive Tactile Sensor for Harsh Environment Applications

KAUST Repository

Alfadhel, Ahmed; Khan, Mohammed Zahed Mustafa; Cardoso, Susana; Leitao, Diana; Kosel, Jü rgen

2016-01-01

A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.

A Magnetoresistive Tactile Sensor for Harsh Environment Applications

KAUST Repository

Alfadhel, Ahmed

2016-05-07

A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR) sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS), is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.

A Magnetoresistive Tactile Sensor for Harsh Environment Applications

Directory of Open Access Journals (Sweden)

Ahmed Alfadhel

2016-05-01

Full Text Available A magnetoresistive tactile sensor is reported, which is capable of working in high temperatures up to 140 °C. Hair-like bioinspired structures, known as cilia, made out of permanent magnetic nanocomposite material on top of spin-valve giant magnetoresistive (GMR sensors are used for tactile sensing at high temperatures. The magnetic nanocomposite, consisting of iron nanowires incorporated into the polymer polydimethylsiloxane (PDMS, is very flexible, biocompatible, has high remanence, and is also resilient to antagonistic sensing ambient. When the cilia come in contact with a surface, they deflect in compliance with the surface topology. This yields a change of the GMR sensor signal, enabling the detection of extremely fine features. The spin-valve is covered with a passivation layer, which enables adequate performance in spite of harsh environmental conditions, as demonstrated in this paper for high temperature.

Hysteresis Curve Fitting Optimization of Magnetic Controlled Shape Memory Alloy Actuator

Directory of Open Access Journals (Sweden)

Fuquan Tu

2016-11-01

Full Text Available As a new actuating material, magnetic controlled shape memory alloys (MSMAs have excellent characteristics such as a large output strain, fast response, and high energy density. These excellent characteristics are very attractive for precision positioning systems. However, the availability of MSMAs in practical precision positioning is poor, caused by weak repeatability under a certain stimulus. This problem results from the error of a large magnetic hysteresis in an external magnetic field. A suitable hysteresis modelling method can reduce the error and improve the accuracy of the MSMA actuator. After analyzing the original hysteresis modelling methods, three kinds of hysteresis modelling methods are proposed: least squares method, back propagation (BP artificial neural network, and BP artificial neural network based on genetic algorithms. Comparing the accuracy and convergence rate of three kinds of hysteresis modelling methods, the results show that the convergence rate of least squares method is the fastest, and the convergence accuracy of BP artificial neural networks based on genetic algorithms is the highest.

Resistivity, hysteresis, and magnetization of 9% Cr stainless steel as a function of temperature and its electromagnetic shielding effects in cylindrical structures

International Nuclear Information System (INIS)

Praeg, W.F.

1979-01-01

Ferromagnetic stainless steels may offer significantly greater wall life-times for first wall/blanket and vacuum vessel structures than commonly used non-magnetic stainless steels. One steel under consideration has the following composition, in wt %, Fe(86.24), Cr(9), Mo(2), Mn(1), Si(0.75), Nb(0.50), V(0.30), C(0.15), P(0.3), S(0.30). There appears to be no literature on the electromagnetic properties of this material. Therefore, the resistivity, the hysteresis loops, and magnetization were measured as a function of temperature up to the Curie point

Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

Science.gov (United States)

Lee, Hyo-Chang

2018-03-01

Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied

Extraordinary magnetoresistance in semiconductor/metal hybrids: A review

KAUST Repository

Sun, J.; Kosel, Jü rgen

2013-01-01

The Extraordinary Magnetoresistance (EMR) effect is a change in the resistance of a device upon the application of a magnetic field in hybrid structures, consisting of a semiconductor and a metal. The underlying principle of this phenomenon is a

Temperature dependence of magnetoresistance in neutron-irradiated and unirradiated high resistivity p-type silicon

International Nuclear Information System (INIS)

Yildirim, M.; Efeoglu, H.; Abay, B.; Yogurtcu, Y.K.

1996-01-01

The temperature dependence of the transverse magnetoresistance in irradiated and unirradiated p-type Si is studied in the range from 120 to 290 K. The magnetoresistance coefficients for the unirradiated left angle 001 right angle and left angle 1 anti 10 right angle samples increases with decreasing sample temperature in the range from 160 to 290 K, however, this behavior is reversed below 160 K. It is proposed that this reversal is due to the double injection effect. The magnetoresistance coefficient for the irradiated left angle 001 right angle sample increases with decreasing sample temperature in the range of 120 to 290 K and is greater than that for the unirradiated left angle 001 right angle sample. This result can be explained by increased scattering due to the increased number of defects produced by irradiation. On the other hand, the magnetoresistance coefficient for the unirradiated left angle 1 anti 10 right angle sample is found to be greater than that of the unirradiated left angle 001 right angle sample. (orig.)

Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP.

Science.gov (United States)

Arnold, Frank; Shekhar, Chandra; Wu, Shu-Chun; Sun, Yan; Dos Reis, Ricardo Donizeth; Kumar, Nitesh; Naumann, Marcel; Ajeesh, Mukkattu O; Schmidt, Marcus; Grushin, Adolfo G; Bardarson, Jens H; Baenitz, Michael; Sokolov, Dmitry; Borrmann, Horst; Nicklas, Michael; Felser, Claudia; Hassinger, Elena; Yan, Binghai

2016-05-17

Weyl semimetals (WSMs) are topological quantum states wherein the electronic bands disperse linearly around pairs of nodes with fixed chirality, the Weyl points. In WSMs, nonorthogonal electric and magnetic fields induce an exotic phenomenon known as the chiral anomaly, resulting in an unconventional negative longitudinal magnetoresistance, the chiral-magnetic effect. However, it remains an open question to which extent this effect survives when chirality is not well-defined. Here, we establish the detailed Fermi-surface topology of the recently identified WSM TaP via combined angle-resolved quantum-oscillation spectra and band-structure calculations. The Fermi surface forms banana-shaped electron and hole pockets surrounding pairs of Weyl points. Although this means that chirality is ill-defined in TaP, we observe a large negative longitudinal magnetoresistance. We show that the magnetoresistance can be affected by a magnetic field-induced inhomogeneous current distribution inside the sample.

Linear magnetoresistance and surface to bulk coupling in topological insulator thin films.

Science.gov (United States)

Singh, Sourabh; Gopal, R K; Sarkar, Jit; Pandey, Atul; Patel, Bhavesh G; Mitra, Chiranjib

2017-12-20

We explore the temperature dependent magnetoresistance of bulk insulating topological insulator thin films. Thin films of Bi 2 Se 2 Te and BiSbTeSe 1.6 were grown using the pulsed laser deposition technique and subjected to transport measurements. Magnetotransport measurements indicate a non-saturating linear magnetoresistance (LMR) behavior at high magnetic field values. We present a careful analysis to explain the origin of LMR taking into consideration all the existing models of LMR. Here we consider that the bulk insulating states and the metallic surface states constitute two parallel conduction channels. Invoking this, we were able to explain linear magnetoresistance behavior as a competition between these parallel channels. We observe that the cross-over field, where LMR sets in, decreases with increasing temperature. We propose that this cross-over field can be used phenomenologically to estimate the strength of surface to bulk coupling.

Power law field dependence of the 2D magnetoresistance in (TMTSF)2PF6

International Nuclear Information System (INIS)

Kriza, G.; Szeghy, G.; Kezsmarki, I.; Mihaly, G.

1999-01-01

The magnetoresistance of the quasi-one-dimensional organic conductor (TMTSF) 2 PF 6 is studied for currents flowing parallel to the best conducting a and second best conducting b directions in magnetic fields perpendicular to the a-b plane under a hydrostatic pressure of 0.8 GPa. As a function of the magnetic field, the magnetoresistance follows a power law ΔR/R = (B/B 0 ) 3/2 both in the a and b directions. The a-b plane conductivity anisotropy is field independent. The scaling field B 0 , characterizing the strength of the magnetoresistance, follows an exponential temperature dependence B 0 ∝exp(T/T 0 ) with a field-independent characteristic temperature T 0 = 10 K. (orig.)

Magnetoresistance in organic semiconductors: Including pair correlations in the kinetic equations for hopping transport

Science.gov (United States)

Shumilin, A. V.; Kabanov, V. V.; Dediu, V. I.

2018-03-01

We derive kinetic equations for polaron hopping in organic materials that explicitly take into account the double occupation possibility and pair intersite correlations. The equations include simplified phenomenological spin dynamics and provide a self-consistent framework for the description of the bipolaron mechanism of the organic magnetoresistance. At low applied voltages, the equations can be reduced to those for an effective resistor network that generalizes the Miller-Abrahams network and includes the effect of spin relaxation on the system resistivity. Our theory discloses the close relationship between the organic magnetoresistance and the intersite correlations. Moreover, in the absence of correlations, as in an ordered system with zero Hubbard energy, the magnetoresistance vanishes.

Magnetoresistance of films and strips with the diffuse surface scattering

International Nuclear Information System (INIS)

Aronov, A.G.

1993-08-01

Magnetoresistance of films in a parallel magnetic field and strips in a perpendicular field is considered. The temperature and magnetic field dependencies of magnetoconductance depend on the time evolution of the correlator of phases. This correlator has different behavior as the function of time: the ergodic behavior at small magnetic fields is changed on the nonergodic one at large magnetic fields in spite of the diffusion electron motion due to a diffuse scattering on boundaries. This leads to unusual temperature and magnetic field dependencies of magnetoresistance. The ergodic hypothesis is not applicable to mesoscopical fluctuations at such a large quasiclassical field. (author). 6 refs, 5 figs

Reorientation response of magnetic microspheres attached to gold electrodes under an applied magnetic field

International Nuclear Information System (INIS)

De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W.; Bustamante Dominguez, A.; Aguiar, J. Albino; Majima, Y.

2013-01-01

In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C 8 H 18 S 2 ), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)

Reorientation response of magnetic microspheres attached to gold electrodes under an applied magnetic field

Energy Technology Data Exchange (ETDEWEB)

De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W., E-mail: luis_d_v@hotmail.com [Cavendish Laboratory, Department of Physics, University of Cambridge Materials and Structures Laboratory (United Kingdom); Bustamante Dominguez, A. [Laboratorio de Ceramicos y Nanomateriales, Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, Lima (Peru); Aguiar, J. Albino [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Fisica; Azuma, Y. [Materials and Structures Laboratory, Tokyo Institute of Technology, Midori-ku, Yokohama (Japan); Majima, Y. [CREST, Japan Science and Technology Agency (JST), Midori-ku, Yokohama (Japan)

2013-08-15

In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C{sub 8}H{sub 18}S{sub 2}), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)

Magnetoresistance measurements of different geometries on epitaxial InP and GaInAs/InP layers

Energy Technology Data Exchange (ETDEWEB)

Somogyi, K. [Hungarian Academy of Sciences, Budapest (Hungary). Research Inst. for Technical Physics

1996-12-31

Hall effect measurement is the main method of the determination of the charge carrier mobility in semiconductors. Magnetoresistance measurements are much less used for the same purpose, perhaps because of the influence of the sample geometry or of the scattering factor differing from the Hall factor. On the other hand, in the case of the epitaxial layers, all these measurements require semi-insulating substrate. In this work two aspects of the magnetoresistance measurements and use of them is demonstrated. First classical geometrical magnetoresistance measurements on InP are studied. On the other hand, a method is presented and applied to sandwich structures in order to measure the geometrical magnetoresistance on epitaxial layers grown on conducting substrates. Resistance of structures metal-epitaxial layer-substrate-metal is measured in the dependence on the angle between the current and magnetic field vectors.

Hysteresis in simulations of malaria transmission

Science.gov (United States)

Yamana, Teresa K.; Qiu, Xin; Eltahir, Elfatih A. B.

2017-10-01

Malaria transmission is a complex system and in many parts of the world is closely related to climate conditions. However, studies on environmental determinants of malaria generally consider only concurrent climate conditions and ignore the historical or initial conditions of the system. Here, we demonstrate the concept of hysteresis in malaria transmission, defined as non-uniqueness of the relationship between malaria prevalence and concurrent climate conditions. We show the dependence of simulated malaria transmission on initial prevalence and the initial level of human immunity in the population. Using realistic time series of environmental variables, we quantify the effect of hysteresis in a modeled population. In a set of numerical experiments using HYDREMATS, a field-tested mechanistic model of malaria transmission, the simulated maximum malaria prevalence depends on both the initial prevalence and the initial level of human immunity in the population. We found the effects of initial conditions to be of comparable magnitude to the effects of interannual variability in environmental conditions in determining malaria prevalence. The memory associated with this hysteresis effect is longer in high transmission settings than in low transmission settings. Our results show that efforts to simulate and forecast malaria transmission must consider the exposure history of a location as well as the concurrent environmental drivers.

Tunnel Magnetoresistance Sensors with Magnetostrictive Electrodes: Strain Sensors.

Science.gov (United States)

Tavassolizadeh, Ali; Rott, Karsten; Meier, Tobias; Quandt, Eckhard; Hölscher, Hendrik; Reiss, Günter; Meyners, Dirk

2016-11-11

Magnetostrictive tunnel magnetoresistance (TMR) sensors pose a bright perspective in micro- and nano-scale strain sensing technology. The behavior of TMR sensors under mechanical stress as well as their sensitivity to the applied stress depends on the magnetization configuration of magnetic tunnel junctions (MTJ)s with respect to the stress axis. Here, we propose a configuration resulting in an inverse effect on the tunnel resistance by tensile and compressive stresses. Numerical simulations, based on a modified Stoner-Wohlfarth (SW) model, are performed in order to understand the magnetization reversal of the sense layer and to find out the optimum bias magnetic field required for high strain sensitivity. At a bias field of -3.2 kA/m under a 0.2 × 10 - 3 strain, gauge factors of 2294 and -311 are calculated under tensile and compressive stresses, respectively. Modeling results are investigated experimentally on a round junction with a diameter of 30 ± 0.2 μ m using a four-point bending apparatus. The measured field and strain loops exhibit nearly the same trends as the calculated ones. Also, the gauge factors are in the same range. The junction exhibits gauge factors of 2150 ± 30 and -260 for tensile and compressive stresses, respectively, under a -3.2 kA/m bias magnetic field. The agreement of the experimental and modeling results approves the proposed configuration for high sensitivity and ability to detect both tensile and compressive stresses by a single TMR sensor.

Negative magnetoresistance in perpendicular of the superlattices axis weak magnetic field at scattering of impurity ions

International Nuclear Information System (INIS)

Askerov, B. M.; Figarova, R.; Guseynov, G.I.

2012-01-01

Full Text : The transverse magnetoresistance in superlattices with the cosine dispersion law of conduction electrons in a case, when a weak magnetic field in plane of layer at scattering of the charge carriers of impurity ions has been studied. It has been shown that in a quasi-two-dimensional case the magnetoresistance was positive, while in a quasi-three-dimensional case can become negative depending of a degree of mini-band filling. Such behavior of magnetoresistance, apparently, has been related to presence in a mini-band of region with the negative effective mass

The Bilinear Product Model of Hysteresis Phenomena

Science.gov (United States)

Kádár, György

1989-01-01

In ferromagnetic materials non-reversible magnetization processes are represented by rather complex hysteresis curves. The phenomenological description of such curves needs the use of multi-valued, yet unambiguous, deterministic functions. The history dependent calculation of consecutive Everett-integrals of the two-variable Preisach-function can account for the main features of hysteresis curves in uniaxial magnetic materials. The traditional Preisach model has recently been modified on the basis of population dynamics considerations, removing the non-real congruency property of the model. The Preisach-function was proposed to be a product of two factors of distinct physical significance: a magnetization dependent function taking into account the overall magnetization state of the body and a bilinear form of a single variable, magnetic field dependent, switching probability function. The most important statement of the bilinear product model is, that the switching process of individual particles is to be separated from the book-keeping procedure of their states. This empirical model of hysteresis can easily be extended to other irreversible physical processes, such as first order phase transitions.

On the controllability of the semilinear heat equation with hysteresis

International Nuclear Information System (INIS)

Bagagiolo, Fabio

2012-01-01

We study the null controllability problem for a semilinear parabolic equation, with hysteresis entering in the semilinearity. Under suitable hypotheses, we prove the controllability result and explicitly treat the cases where the hysteresis relationship is given by a Play or a Preisach operator.

Mixed-phase description of colossal magnetoresistive manganites

Czech Academy of Sciences Publication Activity Database

Weiáe, A.; Loos, Jan; Fehske, H.

2003-01-01

Roč. 68, č. 2 (2003), s. 024402-1 - 021102-6 ISSN 0163-1829 Grant - others:DFG(DE) 436 TSE 113/33/0-2 Institutional research plan: CEZ:AV0Z1010914 Keywords : polarons * metal-insulator transitions * colossal magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.962, year: 2003

Giant magneto-resistance devices

CERN Document Server

Hirota, Eiichi; Inomata, Koichiro

2002-01-01

This book deals with the application of giant magneto-resistance (GMR) effects to electronic devices. It will appeal to engineers and graduate students in the fields of electronic devices and materials. The main subjects are magnetic sensors with high resolution and magnetic read heads with high sensitivity, required for hard-disk drives with recording densities of several gigabytes. Another important subject is novel magnetic random-access memories (MRAM) with non-volatile non-destructive and radiation-resistant characteristics. Other topics include future GMR devices based on bipolar spin transistors, spin field-effect transistors (FETs) and double-tunnel junctions.

Magnetic and transport properties of Fe nanowires encapsulated in carbon nanotubes

International Nuclear Information System (INIS)

Munoz-Sandoval, E.; Lopez-Urias, F.; Diaz-Ortiz, A.; Terrones, M.; Reyes-Reyes, M.; Moran-Lopez, J.L.

2004-01-01

The magnetization reversal and magnetoresistance of two-dimensional arrays of aligned Fe-filled carbon nanotubes have been investigated. Our results show a linear temperature dependence of the coercivity above 10 K and a relative large hysteresis for the applied field perpendicular to the nanowires axes. A continuous decrease of the magnetoresistance for both field directions is observed. We attribute this behavior to the anisotropic nature of the system

Hysteresis of critical currents of superconducting bridges in low perpendicular magnetic fields

International Nuclear Information System (INIS)

Aomine, T.; Tanaka, E.; Yamasaki, S.; Tani, K.; Yonekura, A.

1989-01-01

Hysteresis of critical currents I c of superconducting bridges with In, Nb, and NbN has been studied in low perpendicular magnetic fields. Influences of bridge geometry, small field sweep, trapped flux, and bombardment of argon ions on the hysteresis were made clear. The experimental results suggest that the edge pinning and trapped flux in the bank of bridges are associated with the hysteresis. The peak value of I c of NbN bridges, as well as granular Al and In bridges reported before, in decreasing fields agrees with the calculated pair-breaking current. The origin of the hysteresis is discussed

Hysteresis Compensation of Piezoresistive Carbon Nanotube/Polydimethylsiloxane Composite-Based Force Sensors

Directory of Open Access Journals (Sweden)

Ji-Sik Kim

2017-01-01

Full Text Available This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane dispersed with carbon nanotubes (CNTs, to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied.

The Kurzweil integral and hysteresis

International Nuclear Information System (INIS)

Krejci, P

2006-01-01

A hysteresis operator, called the play, with variable (possibly degenerate) characteristics, is considered in the space of right-continuous regulated functions. The Lipschitz continuity of the input-output mapping is proved by means of a new technique based on the Kurzweil integral

Antisite disorder-induced low-field magnetoresistance in some frustrated Sr2FeMoO6

International Nuclear Information System (INIS)

Cai Tianyi; Ju Sheng; Li Zhenya

2006-01-01

Considering the existence of antiferromagnetic patches induced by the antisite disorder in ferrimagnetic Sr 2 FeMoO 6 , we have developed a resistor network model to account for the effects of the antisite disorder on the magnetoresistance in this material. It is proposed that the magnetic disorder resulting from the existence of frustration around the antiferromagnetic patches will be suppressed under the applied magnetic field and low-field magnetoresistance will be observed. For samples with low levels of antisite defects, the magnetoresistive behaviour may be strongly affected by the different degrees of magnetic inhomogeneity. Our calculated results are in agreement with experimental observations

Angular Magnetoresistance and Hall Measurements in New Dirac Material, ZrSiS

Science.gov (United States)

Ali, Mazhar; Schoop, Leslie; Lotsch, Bettina; Parkin, Stuart

Dirac and Weyl materials have shot to the forefront of condensed matter research in the last few years. Recently, the square-net material, ZrSiS, was theorized and experimentally shown (via ARPES) to host several highly dispersive Dirac cones, including the first Dirac cone demanded by non-symmorphic symmetry in a Si square net. Here we report the magnetoresistance and Hall Effect measurements in this compound. ZrSiS samples with RRR = 40 were found to have MR values up to 6000% at 2 K, be predominantly p-type with a carrier concentration of ~8 x 1019 cm-3 and mobility ~8500 cm2/Vs. Angular magnetoresistance measurements reveal a peculiar behavior with multiple local maxima, depending on field strength, indicating of a sensitive and sensitive Fermi surface. SdH oscillations analysis confirms Hall and angular magnetoresistance measurements. These results, in the context of the theoretical and ARPES results, will be discussed.

Symmetric wetting heterogeneity suppresses fluid displacement hysteresis in granular piles

Science.gov (United States)

Moosavi, R.; Schröter, M.; Herminghaus, S.

2018-02-01

We investigate experimentally the impact of heterogeneity on the capillary pressure hysteresis in fluid invasion of model porous media. We focus on symmetric heterogeneity, where the contact angles the fluid interface makes with the oil-wet (θ1) and the water-wet (θ2) beads add up to π . While enhanced heterogeneity is usually known to increase hysteresis phenomena, we find that hysteresis is greatly reduced when heterogeneities in wettability are introduced. On the contrary, geometric heterogeneity (like bidisperse particle size) does not lead to such an effect. We provide a qualitative explanation of this surprising result, resting on rather general geometric arguments.

Efficient Use of Preisach Hysteresis Model in Computer Aided Design

Directory of Open Access Journals (Sweden)

IONITA, V.

2013-05-01

Full Text Available The paper presents a practical detailed analysis regarding the use of the classical Preisach hysteresis model, covering all the steps, from measuring the necessary data for the model identification to the implementation in a software code for Computer Aided Design (CAD in Electrical Engineering. An efficient numerical method is proposed and the hysteresis modeling accuracy is tested on magnetic recording materials. The procedure includes the correction of the experimental data, which are used for the hysteresis model identification, taking into account the demagnetizing effect for the sample that is measured in an open-circuit device (a vibrating sample magnetometer.

Temperature-dependent gate-swing hysteresis of pentacene thin film transistors

Directory of Open Access Journals (Sweden)

Yow-Jon Lin

2014-10-01

Full Text Available The temperature-dependent hysteresis-type transfer characteristics of pentacene-based organic thin film transistors (OTFTs were researched. The temperature-dependent transfer characteristics exhibit hopping conduction behavior. The fitting data for the temperature-dependent off-to-on and on-to-off transfer characteristics of OTFTs demonstrate that the hopping distance (ah and the barrier height for hopping (qϕt control the carrier flow, resulting in the hysteresis-type transfer characteristics of OTFTs. The hopping model gives an explanation of the gate-swing hysteresis and the roles played by qϕt and ah.

Energy Barriers and Hysteresis in Martensitic Phase Transformations

Science.gov (United States)

2008-08-01

glacial acetic acid (CH3COOH) and 10-15% perchloric acid (HCLO4) by volume, the cathode was stainless steel , the anode was stainless steel or Ti, the...Submitted to Acta Materialia Energy barriers and hysteresis in martensitic phase transformations Zhiyong Zhang, Richard D. James and Stefan Müller...hysteresis based on the growth from a small scale of fully developed austenite martensite needles. In this theory the energy of the transition layer plays a

Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

Directory of Open Access Journals (Sweden)

Sergio Iván Ravelo Arias

2013-12-01

Full Text Available Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function  is obtained considering it as the relationship between sensor output voltage and input sensing current,[PLEASE CHECK FORMULA IN THE PDF]. The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR, giant magnetoresistance (GMR, spin-valve (GMR-SV and tunnel magnetoresistance (TMR. The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications.

Mobility controlled linear magnetoresistance with 3D anisotropy in a layered graphene pallet

KAUST Repository

Zhang, Qiang

2016-09-27

A bulk sample of pressed graphene sheets was prepared under hydraulic pressure (similar to 150 MPa). The cross-section of the sample demonstrates a layered structure, which leads to 3D electrical transport properties with anisotropic mobility. The electrical transport properties of the sample were measured over a wide temperature (2-400 K) and magnetic field (-140 kOe <= H <= 140 kOe) range. The magnetoresistance measured at a fixed temperature can be described by R(H, theta) = R(epsilon H-theta, 0) with epsilon(theta) =(cos(2)theta + gamma(-2) sin(2)theta)(1/2), where gamma is the mobility anisotropy constant and theta is the angle between the normal of the sample plane and the magnetic field. The large linear magnetoresistance (up to 36.9% at 400 K and 140 kOe) observed at high fields is ascribed to a classical magnetoresistance caused by mobility fluctuation (Delta mu). The magnetoresistance value at 140 kOe was related to the average mobility () because of the condition Delta mu < . The carrier concentration remained constant and the temperature-dependent resistivity was proportional to the average mobility, as verified by Kohler\\'s rule. Anisotropic dephasing length was deduced from weak localization observed at low temperatures.

Anomalous Hall effect and magnetoresistance behavior in Co/Pd1−xAgx multilayers

KAUST Repository

Guo, Z. B.

2013-02-13

In this paper, we report anomalous Hall effect (AHE) correlated with the magnetoresistance behavior in [Co/Pd1-xAg x]n multilayers. For the multilayers with n = 6, the increase in Ag content from x = 0 to 0.52 induces the change in AHE sign from negative surface scattering-dominated AHE to positive interface scattering-dominated AHE, which is accompanied with the transition from anisotropy magnetoresistance (AMR) dominated transport to giant magnetoresistance (GMR) dominated transport. For n = 80, scaling analysis with Rs ∝ρ xx γ yields γ ∼ 3.44 for x = 0.52 which presents GMR-type transport, in contrast to γ ∼ 5.7 for x = 0 which presents AMR-type transport. © 2013 American Institute of Physics.

Apparent negative magnetoresistance without independent Weyl pockets in the Weyl semimetal TaP

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