Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field

Science.gov (United States)

Banerjee, Ananya; Sarkar, A.

2016-05-01

The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.

Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Ananya, E-mail: banerjee.ananya2008@gmail.com; Sarkar, A. [Dept. of Physics, Bijoy Krishna Girls’ College, 5/3 M.G. Road, Howrah 711101, W.B. (India)

2016-05-06

The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.

Magnetic properties of permalloy films with different thicknesses deposited onto obliquely sputtered Cu underlayers

International Nuclear Information System (INIS)

Li, Xiaoyu; Sun, Xiaojun; Wang, Jianbo; Liu, Qingfang

2015-01-01

In this work, the influence of obliquely sputtered Cu underlayer of 10 nm on the magnetic properties of normally sputtered Permalloy thin films with different thicknesses from 10 nm to 150 nm has been investigated. It has been found that the samples with the Permalloy layer thickness ranging from 10 nm to 70 nm exhibit a good in-plane uniaxial magnetic anisotropy, and the increase of the film thickness leads to a decrease of the anisotropy field and the natural resonance frequency. The critical Permalloy layer thickness for stripe domain initiation of these films is about 80 nm, which is thinner than that of obliquely sputtered Permalloy thin films without an underlayer. The characteristic shapes of hysteresis loops which can be called ''transcritical'' are observed above the critical thickness. The condition and mechanism of appearing stripe domain structure were discussed and it has been found that the frequency response of permeability of the anisotropic films shows the characteristics of multi-peak resonance. - Highlights: • Py films were fabricated on obliquely sputtered Cu underlayers by RF magnetron sputtering. • Effects of Py layer thickness on anisotropy, ferromagnetic resonance frequency have been studied. • Samples with Py layer (<70 nm) show a good in-plane uniaxial magnetic anisotropy. • Samples with Py layer (>80 nm) show stripe domains and multi-peaks in permeability spectra

High-frequency electromagnetic properties of soft magnetic metal-polyimide hybrid thin films

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang Woo [Nano-Materials Research Center, Korea Institute of Science and Technology, 39-1 Haweoulgog-dong, Sungbuk-gu, Seoul 136-791 (Korea, Republic of)]. E-mail: swkim@kist.re.kr; Yoon, Chong S. [Division of Advanced Materials Science, Hanyang University, Seoul 133-791 (Korea, Republic of)

2007-09-15

Although there are a lot of demands for suppression of unwanted high-frequency electromagnetic noise in highly integrated electronic devices such as mobile phones and notebook computers, electromagnetic thin films that effectively work in the high-frequency range have still been underdeveloped. Soft magnetic metal-polyimide (PI) hybrid films with high electrical resistivity were prepared by thermal imidization and selective oxidation between the metal alloy layer and polyamic acid (PAA) layer. Electromagnetic properties of the hybrid thin films in the radio-frequency range were characterized by using the microstrip line method and were correlated with their material parameters. Although anisotropy field of the CoFe/NiFe hybrid film was two times lower than that of the NiFe hybrid film, the saturation magnetization of the CoFe/NiFe hybrid film was three times higher than that of the NiFe hybrid film. The CoFe/NiFe hybrid film showed higher power loss in the frequency range of 3-6 GHz compared to the NiFe hybrid film. The high power loss of the CoFe/NiFe hybrid film was caused by high relative permeability and high ferromagnetic resonance (FMR) frequency due to high saturation magnetization.

High-frequency electromagnetic properties of soft magnetic metal-polyimide hybrid thin films

International Nuclear Information System (INIS)

Kim, Sang Woo; Yoon, Chong S.

2007-01-01

Although there are a lot of demands for suppression of unwanted high-frequency electromagnetic noise in highly integrated electronic devices such as mobile phones and notebook computers, electromagnetic thin films that effectively work in the high-frequency range have still been underdeveloped. Soft magnetic metal-polyimide (PI) hybrid films with high electrical resistivity were prepared by thermal imidization and selective oxidation between the metal alloy layer and polyamic acid (PAA) layer. Electromagnetic properties of the hybrid thin films in the radio-frequency range were characterized by using the microstrip line method and were correlated with their material parameters. Although anisotropy field of the CoFe/NiFe hybrid film was two times lower than that of the NiFe hybrid film, the saturation magnetization of the CoFe/NiFe hybrid film was three times higher than that of the NiFe hybrid film. The CoFe/NiFe hybrid film showed higher power loss in the frequency range of 3-6 GHz compared to the NiFe hybrid film. The high power loss of the CoFe/NiFe hybrid film was caused by high relative permeability and high ferromagnetic resonance (FMR) frequency due to high saturation magnetization

Stress state evaluation in low carbon and TRIP steels by magnetic permeability

International Nuclear Information System (INIS)

Kouli, M.-E.; Giannakis, M

2016-01-01

Magnetic permeability is an indicative factor for the steel health monitoring. The measurements of magnetic permeability lead to the evaluation of the stress state of any ferromagnetic steel. The magnetic permeability measurements were conducted on low carbon and TRIP steel samples, which were subjected to both tensile and compressive stresses. The results indicated a direct correlation of the magnetic permeability with the mechanical properties, the stress state and the microstructural features of the examined samples. (paper)

Simultaneous inversion of airborne electromagnetic data for resistivity and magnetic permeability

International Nuclear Information System (INIS)

Beard, L.P.; Nyquist, J.E.

1998-01-01

Where the magnetic permeability of rock or soil exceeds that of free space, the effect on airborne electromagnetic systems is to produce a frequency-independent shift in the in-phase response of the system while altering the quadrature response only slightly. The magnitude of the in-phase shift increases as (1) the relative magnetic permeability is increased, (2) the amount of magnetic material is increased, and (3) the airborne sensor gets nearer the earth's surface. Over resistive, magnetic ground, the shift may be evinced by negative in-phase measurements at low frequencies; but over more conductive ground, the same shift may go unnoticed because of the large positive in-phase response. If the airborne sensor is flown at low levels, the magnitude of the shift may be large enough to affect automatic inversion routines that do not take this shift into account, producing inaccurate estimated resistivities, usually overestimates. However, layered-earth inversion algorithms that incorporate magnetic permeability as an additional inversion parameter may improve the resistivity estimates. The authors demonstrate this improvement using data collected over hazardous waste sites near Oak Ridge, Tennessee, USA. Using resistivity inversion without magnetic permeability, the waste sites are almost invisible to the sensors. When magnetic permeability is included as an inversion parameter, the sites are detected, both by improved resistivity estimates and by estimated magnetic permeability

Artificially controlled stress anisotropy and magnetic properties of FeTaN thin films

International Nuclear Information System (INIS)

Deng, H.; Jarratt, J.D.; Minor, M.K.; Barnard, J.A.

1997-01-01

This article presents a new method of investigating internal stress effects on thin film magnetic properties, in this case magnetically soft FeTaN sputtered films. The FeTaN films were deposited on a series of oxidized silicon (111) substrates prestressed to different degrees. During sputtering all the deposition conditions were kept exactly the same for all the samples. However, anisotropic stresses with different amplitudes are systematically introduced into the films when the prestressed wafers were released. In this way, FeTaN films with compressive stress varying from 80 to 608 MPa are produced. We found that the saturation magnetostriction (λ s ), anisotropy field (H k ), initial permeability (μ i ) as well as easy axis orientation of FeTaN thin films are strongly affected by the induced stress anisotropy. A stress ratio concept is proposed as a measure of the degree of the stress anisotropy. Models for easy-hard axis switching induced by stress for magnetic films with positive magnetostriction are discussed. copyright 1997 American Institute of Physics

Electrical conductivity and magnetic permeability measurement of case hardened steels

Science.gov (United States)

Tian, Yong

2015-03-01

For case carburized steels, electrical conductivity and magnetic permeability profiles are needed to develop model-based case depth characterization techniques for the purpose of nondestructive quality control. To obtain fast and accurate measurement of these material properties, four-point potential drop approaches are applied on circular-shaped discs cut from steel rings with different case depths. First, a direct current potential drop (DCPD) approach is applied to measure electrical conductivity. Subsequently, an alternating current potential drop (ACPD) approach is used to measure magnetic permeability. Practical issues in measurement design and implementation are discussed. Depth profiles of electrical conductivity and magnetic permeability are reported.

High-frequency permeability in double-layered structure of amorphous Co-Ta-Zr films

International Nuclear Information System (INIS)

Ochiai, Y.; Hayakawa, M.; Hayashi, K.; Aso, K.

1988-01-01

The high-frequency permeability of amorphous Co-Ta-Zr films was studied and the frequency dependence was described in terms of the eddy-current-loss formula. For the double-layered structure intervened with SiO 2 film, the degradation of the permeability became apparent with the decrease of SiO 2 thickness

Magnetic and other properties and sputtering behavior of Co-base amorphous alloy films

International Nuclear Information System (INIS)

Hayashi, K.; Hayakawa, M.; Ochiai, Y.; Matsuda, H.; Ishikawa, W.; Iwasaki, Y.; Aso, K.

1987-01-01

Magnetic and other properties of Co-base amorphous alloy films prepared by sputtering are investigated. A detailed magnetic phase diagram with saturation magnetic flux density, crystallization temperature, and zero-magnetostrictive line on Co-Ta-Zr amorphous alloys were obtained, and the technical knowhow to make a film with well-reproducible characteristics by widely changing the sputtering conditions was related with these physical properties. Especially on alloy sputtering, a phenomenological model for elucidating a composition difference between film and target is presented. After these studies, the film characteristics of B/sub s/ = 12 kG, T/sub x/ = 450 0 C, chemical bondλ/sub s/chemical bond -8 , H/sub c/<10 mOe, and permeabilities of μ(1 MHz) = 7000, μ(100 MHz) = 2000 for the single film of 2 μm in thickness and of μ(1 MHz) = 4000, μ(100 MHz) = 800 for the insulator-sandwiched multilayered film of 10 μm are obtained, and these well-balanced values enable us to apply the materials for high-frequency recording head

Structure and soft magnetic properties of sputter deposited MnZn-ferrite films

NARCIS (Netherlands)

Gillies, M.F.; Coehoorn, R.; van Zon, J.B.A.D.; Alders, D.

1998-01-01

In this paper we report the soft magnetic properties of thin films of sputtered MnZn ferrite deposited on thermally oxidized Si substrates. A high deposition temperature, 600¿°C, together with the addition of water vapor to the sputtering gas was found to improve the initial ac permeability, µ. The

Permeability and stress-jump effects on magnetic drug targeting in a permeable microvessel using Darcy model

Energy Technology Data Exchange (ETDEWEB)

Shaw, S., E-mail: sachinshaw@gmail.com [Department of Mathematics and Statistical Sciences, Botswana International University of Science and Technology, Private Bag 16, Palapye (Botswana); Sutradhar, A.; Murthy, PVSN [Department of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal (India)

2017-05-01

In the present paper, we investigated the influence of permeability of the carrier particle and stress jump condition on the porous spherical surface in magnetic drug targeting through a permeable microvessel. The nature of blood is defined by non-Newtonian Casson fluid in the core region of the microvessel and Newtonian fluid in the peripheral region which is located near the surface of the wall of the microvessel. The magnetic particles are considered as spherical and in nanosize, embedded in the carrier particle along with drug particles. A magnet is placed near the tumor position to generate a magnetic field. The relative motion of the carrier particle is the resultant of the fluidic force, magnetic force and Saffman drag force which are calculated for the spherical carrier particle. Trajectories of the carrier particle along the radial and axial direction are calculated. Effect of different parameters such as stress-jump constant, permeability of the carrier particle, pressure gradient, yield stress, Saffman force, volume fraction of the embedded magnetic nanoparticles, permeability of the microvessel wall, and the radius of the carrier particle on the trajectory of the carrier particle are discussed and displayed graphically. - Highlights: • In the present manuscript, we considered the porous carrier particle which provide a larger surface area contact with the fluid than the solid spherical carrier particle. It shows that the porous carrier particle are captured easily than the solid carrier particle. • Introduce Suffman force on the carrier particle which commences an additional resistance which acts opposite to the surface wall and helps the particles to go away from the tumor position. • Considered stress jump condition at the surface of the porous carrier particle which enhanced the tendency of the carrier particle to be capture near the tumor. • Used Darcy model to define the permeability of the wall of the microvessel.

Tunable d-Limonene Permeability in Starch-Based Nanocomposite Films Reinforced by Cellulose Nanocrystals.

Science.gov (United States)

Liu, Siyuan; Li, Xiaoxi; Chen, Ling; Li, Lin; Li, Bing; Zhu, Jie

2018-01-31

In order to control d-limonene permeability, cellulose nanocrystals (CNC) were used to regulate starch-based film multiscale structures. The effect of sphere-like cellulose nanocrystal (CS) and rod-like cellulose nanocrystal (CR) on starch molecular interaction, short-range molecular conformation, crystalline structure, and micro-ordered aggregated region structure were systematically discussed. CNC aspect ratio and content were proved to be independent variables to control d-limonene permeability via film-structure regulation. New hydrogen bonding formation and increased hydroxypropyl starch (HPS) relative crystallinity could be the reason for the lower d-limonene permeability compared with tortuous path model approximation. More hydrogen bonding formation, higher HPS relative crystallinity and larger size of micro-ordered aggregated region in CS0.5 and CR2 could explain the lower d-limonene permeability than CS2 and CR0.5, respectively. This study provided new insight for the control of the flavor release from starch-based films, which favored its application in biodegradable food packaging and flavor encapsulation.

Ultrasoft and High Magnetic Moment CoFe Films Directly Electrodeposited from a B-Reducer Contained Solution

Directory of Open Access Journals (Sweden)

Baoyu Zong

2008-01-01

Full Text Available A methodology to fabricate ultrasoft CoFe nano-/microfilms directly via electrodeposition from a semineutral iron sulfate solution is demonstrated. Using boron-reducer as the additive, the CoFe films become very soft with high magnetic moment. Typically, the film coercivity in the easy and hard axes is 6.5 and 2.5 Oersted, respectively, with a saturation polarization up to an average of 2.45 Tesla. Despite the softness, these shining and smooth films still display a high-anisotropic field of ~45 Oersted with permeability up to 104. This kind of films can potentially be used in current and future magnetic recording systems as well as microelectronic and biotechnological devices.

Simulation of the contribution of magnetic films on planar inductors characteristics

International Nuclear Information System (INIS)

Gamet, E.; Chatelon, J.P.; Rouiller, T.; Bayard, B.; Noyel, G.; Rousseau, J.J.

2005-01-01

We propose here to use the interesting properties of magnetic thin films in order to improve planar inductors characteristics. Magnetic thin films serve as a way of confining electromagnetic field into the coil.Radio-frequency components require high-quality inductors. But at high frequencies several effects degrade the quality factor (Q) of the inductor. Our investigation deals with planar inductors, and we first try to optimize methodology of inductors design. The inductor area is kept constant (300x300μm 2 ). Characteristics of spiral inductors heavily depend on coils structures (thickness, width, number of loops, shape ...). The impact of spiral inductor parameters on the L and Q factors is studied. Q profit can reach 100% after coils parameters optimization.On the other hand, different designs with magnetic films are tested. The relative permeability (μr) of magnetic material is set to 10 and dielectric/magnetic losses are assumed to be negligeable. Thicknesses of about 10μm of magnetic material are reasonable in terms of technology and especially compatible with integration. At 2GHz, with 10μm under the coils, L and Q values have a profit of 44% and 9%, respectively compared to the non magnetic-structure.The results are based on RL model and are obtained from simulations (Ansoft HFSS) for frequencies up to 5GHz

Size optimization for complex permeability measurement of magnetic thin films using a short-circuited microstrip line up to 30 GHz

Science.gov (United States)

Takeda, Shigeru; Naoe, Masayuki

2018-03-01

High-frequency permeability spectra of magnetic films were measured over a wideband frequency range of 0.1-30 GHz using a shielded and short-circuited microstrip line jig. In this measurement, spurious resonances had to be suppressed up to the highest frequency. To suppress these resonances, characteristic impedance of the microstrip line should approach 50 Ω at the junction between connector and microstrip line. The main factors dominating these resonances were structures of the jig and the sample. The dimensions were optimized in various experiments, and results demonstrated that the frequency could be raised to at least 20 GHz. For the transverse electromagnetic mode to transmit stably along the microstrip line, the preferred sample was rectangular, with the shorter side parallel to the line and the longer side perpendicular to it, and characteristic impedance strongly depended on the signal line width of the jig. However, too small a jig and sample led to a lower S/N ratio.

Correlating elastic and plastic deformation with magnetic permeability values

Science.gov (United States)

Papadopoulou, S.

2017-12-01

This paper investigates the utilization of magnetic permeability method in determining elastic and plastic deformation state of ferromagnetic steels. The results have shown a strong degradation of the magnetic values on plastically region due to the irreversible movements of the magnetic domain walls.

Color-magnetic permeability of QCD vacuum

Energy Technology Data Exchange (ETDEWEB)

Saito, T [Kyoto Prefectural Univ. of Medicine (Japan); Shigemoto, K

1980-03-01

In the very strong background gauge field the QCD true vacuum has been shown to have lower energy than the ''perturbative vacuum.'' The color-magnetic permeability of the QCD true vacuum is then calculated to be 1/2 within the quark-one-loop approximation.

Dynamic magnetization of NiZn ferrite doped FeSiAl thin films fabricated by oblique sputtering

Energy Technology Data Exchange (ETDEWEB)

Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China); Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Soh, Wee Tee [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Ong, C.K. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Li, Lezhong [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

2017-06-15

Highlights: • We prepared NiZn ferrite doped FeSiAl-based thin films using oblique deposition technique. • The magnetic properties of FeSiAl-based thin films were systematically studied. • Two ferromagnetic resonance peaks were observed in the permeability spectra. • The thermal stability of microwave properties of FeSiAl-based films was studied. • The thermal stability of properties we studied was relatively good. - Abstract: In this study, we comprehensively investigate the dynamic magnetic properties of FeSiAl-NiZnFeO thin films prepared by the oblique deposition method via a shorted microstrip perturbation technique. For the films with higher oblique angle and NiZn ferrite doping amount, there are two ferromagnetic resonance peaks observed in the permeability spectra, and both of the two peaks originate from FeSiAl. Furthermore, the magnetic anisotropy field H{sub K} of the ferromagnetic resonance peak at higher frequency is enhanced with increasing doping amount, which is interpreted in terms of the contribution of reinforced stress-induced anisotropy and shape anisotropy brought about by doping elements and oblique sputtering method. In addition, the thermal stability of the ferromagnetic resonance frequency f{sub FMR} of FeSiAl-NiZnFeO films with oblique angles of 35° and 45° with respect to temperature ranging from 300 K to 420 K is deteriorated with increasing ferrite doping amount, which is mainly ascribed to the influence of pair-ordering anisotropy and/or the reduction of the FeSiAl grain size.

Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

International Nuclear Information System (INIS)

Yu, Ying; Zhan, Qingfeng; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Wang, Baomin; Li, Run-Wei; Wei, Jinwu; Wang, Jianbo; Xie, Shuhong

2015-01-01

Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices

Static and high frequency magnetic properties of FeGa thin films deposited on convex flexible substrates

Science.gov (United States)

Yu, Ying; Zhan, Qingfeng; Wei, Jinwu; Wang, Jianbo; Dai, Guohong; Zuo, Zhenghu; Zhang, Xiaoshan; Liu, Yiwei; Yang, Huali; Zhang, Yao; Xie, Shuhong; Wang, Baomin; Li, Run-Wei

2015-04-01

Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2 GHz. Our investigations demonstrated a convenient method via the pre-strained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices.

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

Energy Technology Data Exchange (ETDEWEB)

Vasilevskaya, Tatiana M., E-mail: t_vasilevs@mail.ru [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation); Sementsov, Dmitriy I.; Shutyi, Anatoliy M. [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation)

2012-09-15

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: Black-Right-Pointing-Pointer An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. Black-Right-Pointing-Pointer Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. Black-Right-Pointing-Pointer Both regular and chaotic precession modes are realized within bifurcation resonance range. Black-Right-Pointing-Pointer Appearance of dynamic bistability is typical for bifurcation resonance.

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

International Nuclear Information System (INIS)

Vasilevskaya, Tatiana M.; Sementsov, Dmitriy I.; Shutyi, Anatoliy M.

2012-01-01

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: ► An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. ► Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. ► Both regular and chaotic precession modes are realized within bifurcation resonance range. ► Appearance of dynamic bistability is typical for bifurcation resonance.

Estimation of non-linear effective permeability of magnetic materials with fine structure

International Nuclear Information System (INIS)

Waki, H.; Igarashi, H.; Honma, T.

2006-01-01

This paper describes a homogenization method for magnetic materials with fine structure. In this method, the structures of the magnetic materials are assumed to be periodic, and the unit cell is defined. The effective permeability is determined on the basis of magnetic energy balance in the unit cell. This method can be applied not only for linear problems but also for non-linear ones. In this paper, estimation of the effective permeability of non-linear magnetic materials by using the homogenization method is described in detail, and then the validity for the non-liner problems is tested for two-dimensional problems. It is shown that this homogenization method gives accurate non-linear effective permeability

Mechanical and permeability properties of milk protein films

Directory of Open Access Journals (Sweden)

Marília I.S. Folegatti

1998-01-01

Full Text Available Edible films present a potential alternative for replacing plastic films used for packaging in food industry. One of the major advantages is the environmental appeal of this technology, which produces no packaging waste. Some films made with other edible materials have found commercial applications, and many more are being developed using a myriad of food based components. This paper focuses on some important characteristics of films produced with sodium and calcium caseinates. The effects of caseinate type and concentration, plasticizer concentration and pH were studied. Major parameters investigated were solubility, tensile properties, water vapour and oxygen permeabilities. Caseinate films showed high solubility at pH range 6.0-8.0 and complete insolubility at pH 3.0 and 4.0. Calcium caseinate films had a higher tensile strength and a lower % elongation at break than sodium caseinate films. There was not significant difference in water vapour and oxygen permeabilities between sodium and calcium caseinate films.Filmes comestíveis representam uma alternativa potencial para a substituição de filmes plásticos .empregados em embalagem de alimentos. Uma de suas maiores vantagens relaciona-se com o problema de poluição ambiental por não gerar material residual. Filmes elaborados com outros materiais comestíveis não protéicos têm encontrado aplicação comercial e muitos outros ainda estão sendo pesquisados, usando uma grande variedade de componentes alimentares. Este trabalho estuda algumas características importantes dos filmes produzidos com caseinatos de sódio e de cálcio. Os efeitos do tipo e concentração de caseinato, concentração de plastificante e do pH são investigados. Os parâmetros pesquisados foram a solubilidade, propriedades de tração e permeabilidade a vapor de água e oxigênio. Filmes de caseinato apresentaram alta solubilidade na faixa de pH entre 6.0 e 8.0 e completa insolubilidade em pH 3.0 e 4.0. Maior

Water sorption and water permeability properties of edible film made from potato peel waste

Directory of Open Access Journals (Sweden)

Siti Hajar OTHMAN

Full Text Available Abstract The water sorption and permeability properties of edible film produced from potato peel waste was investigated under different levels of relative humidity (23, 33, 43, 57, 75% RH and temperatures (5, 30, 50 °C. The water sorption behaviour and isotherms of the film were investigated by fitting water sorption data to the Peleg model and the Guggenheim, Anderson de Boer model (GAB model. The amount of moisture content, time required for the moisture content of the film to reach equilibrium, water sorption rate, and water sorption capacity increased when the relative humidity increased. The effect of temperature on moisture content, water sorption rate, water sorption capacity, and monolayer moisture content is complex and related to the water activity as well as the moisture content. Based on R2 and RMSE values, the Peleg and GAB models were respectively determined as excellent models to predict the water sorption properties of the films, thus supporting the reliability of water sorption behaviour prediction. The water vapour transmission rate and water vapour permeability increased with an increase in relative humidity and temperature. The sorption and permeability properties of the film are worth investigation since the final application of the film as food packaging is ultimately dependent on these behaviours.

Tunable Gas Permeability of Polymer-Clay Nano Brick Wall Thin Film Assemblies

Science.gov (United States)

Gamboa, Daniel; Priolo, Morgan; Grunlan, Jaime

2010-03-01

Thin films of anionic natural montmorrilonite (MMT) clay and cationic polyethylenimine (PEI) have been produced by alternately dipping a plastic substrate into dilute aqueous mixtures containing each ingredient. After 40 polymer-clay layers have been deposited, the resulting transparent film exhibits an oxygen transmission rate (OTR) below 0.35 cm^3/m^2 . day when the pH of PEI solution is 10. This low permeability is due to a brick wall nanostructure comprised of completely exfoliated clay bricks in polymeric mortar. This brick wall creates an extremely tortuous path at thicknesses below 250 nm and clay concentration above 80 wt%. A 70-bilayer PEI-MMT assembly has an undetectable OTR (< 0.005 cm^3/m^2 . day), which equates to a permeability below SiOx when multiplied by its film thickness of 231 nm. With optical transparency greater than 86% and the ability to be microwaved, these thin film composites are good candidates for flexible electronics packaging and foil replacement for food.

Magnetization Controlled Superconductivity in a Film with Magnetic Dots

International Nuclear Information System (INIS)

Lyuksyutov, I.F.; Pokrovsky, V.; Pokrovsky, V.

1998-01-01

We consider a superconducting film with a magnetic dots array (MDA) placed upon it. Magnetic moments of the dots are normal to the film and strong enough to create vortices in the superconducting film. Magnetic interaction between dots is negligible. Zero-field cooling leads to random magnetization of the MDA well above the superconducting temperature. With this cooling, the film is in a resistive state below the (expected) superconducting transition. Paradoxically, when field cooled, the film with MDA can be superconducting. copyright 1998 The American Physical Society

Effect of gas type on foam film permeability and its implications for foam flow in porous media.

Science.gov (United States)

Farajzadeh, R; Muruganathan, R M; Rossen, W R; Krastev, R

2011-10-14

The aim of this paper is to provide a perspective on the effect of gas type on the permeability of foam films stabilized by different types of surfactant and to present a critical overview of the tracer gas experiments, which is the common approach to determine the trapped fraction of foam in porous media. In these experiments some part of the gas is replaced by a "tracer gas" during the steady-state stage of the experiments and trapped fraction of foam is determined by fitting the effluent data to a capacitance mass-transfer model. We present the experimental results on the measurement of the gas permeability of foam films stabilized with five surfactants (non-ionic, anionic and cationic) and different salt concentrations. The salt concentrations assure formation of either common black (CBF) or Newton black films (NBF). The experiments are performed with different single gasses. The permeability of the CBF is in general higher than that of the NBF. This behavior is explained by the higher density of the surfactant molecules in the NBF compared to that of CBF. It is also observed that the permeability coefficient, K(cm/s), of CBF and NBF for non-ionic and cationic surfactants are similar and K is insensitive to film thickness. Compared to anionic surfactants, the films made by the non-ionic surfactant have much lower permeability while the films made by the cationic surfactant have larger permeability. This conclusion is valid for all gasses. For all types of surfactant the gas permeability of foam film is largely dependent on the dissolution of gas in the surfactant solution and increases with increasing gas solubility in the bulk liquid. The measured values of K are consistent with rapid diffusion of tracer gasses through trapped gas adjacent to flowing gas in porous media, and difficulties in interpreting the results of tracer-foam experiments with conventional capacitance models. The implications of the results for foam flow in porous media and factors leading

Influence of demagnetizing field on the permeability of soft magnetic composites

International Nuclear Information System (INIS)

Lin, G.Q.; Li, Z.W.; Chen, Linfeng; Wu, Y.P.; Ong, C.K.

2006-01-01

The influence of demagnetizing field on the effective permeability of magnetic composites has been investigated. A theoretical expression of the effective permeability has been obtained and discussed according to four typical composites with spheres, needles, flakes, and aligned prolate ellipsoidal particles. The results indicate that the demagnetizing field within the particles can reduce the effective permeability significantly. In order to increase the effective permeability, it is necessary to decrease the demagnetizing field within the particles. A linear relationship between effective permeability and volume fraction is also observed for composites filled with spherical particles at low volume fraction

Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy

Science.gov (United States)

Lopez-Lopez, M. T.; Nogueras-Lara, F.; Rodriguez-Arco, L.; Guigo, N.; Sbirrazzuoli, N.; Zubarev, A. Yu.; Lacis, S.; Kuzhir, P.

2017-12-01

Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e., ferrofluids, can be assembled into different types of structures upon application of an external magnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point-dipole approximation for the magnetic interactions between microbeads mediated by the ferrofluid; however, the ferrofluid is considered to possess an anisotropic magnetic permeability thanks to field-induced structuring of its nanoparticles. The model is tested against experimental results and shows generally better agreement with experiments than the model considering isotropic magnetic permeability of ferrofluids. The results could be useful for understanding kinetics of aggregation of microbeads suspended in a ferrofluid. From a broader perspective, the present study is believed to contribute to a general understanding of particle behaviors in anisotropic media.

Error Analysis of High Frequency Core Loss Measurement for Low-Permeability Low-Loss Magnetic Cores

DEFF Research Database (Denmark)

Niroumand, Farideh Javidi; Nymand, Morten

2016-01-01

in magnetic cores is B-H loop measurement where two windings are placed on the core under test. However, this method is highly vulnerable to phase shift error, especially for low-permeability, low-loss cores. Due to soft saturation and very low core loss, low-permeability low-loss magnetic cores are favorable...... in many of the high-efficiency high power-density power converters. Magnetic powder cores, among the low-permeability low-loss cores, are very attractive since they possess lower magnetic losses in compared to gapped ferrites. This paper presents an analytical study of the phase shift error in the core...... loss measuring of low-permeability, low-loss magnetic cores. Furthermore, the susceptibility of this measurement approach has been analytically investigated under different excitations. It has been shown that this method, under square-wave excitation, is more accurate compared to sinusoidal excitation...

Magnetization reversal mechanism of Nd-Fe-B films with perpendicular magnetic anisotropy

International Nuclear Information System (INIS)

Liu Xiaoxi; Ishida, Go; Morisako, Akimitsu

2011-01-01

The microstructure and magnetic properties of Nd-Fe-B films with thicknesses from 100 nm to 3 nm have been investigated. All the films show excellent perpendicular magnetic anisotropy with a squareness ratio of 1 in the perpendicular direction and almost zero coercivity in the in-plane direction. Of particular interest is that the initial magnetization curves sensitively depended on the film thickness. Films thicker than 15 nm show steep initial magnetization curve. Although the films have coercivities larger than 21 kOe, the films can be fully magnetized from the thermally demagnetized state with a field as small as 5 kOe. With the decrease of film thickness to 5 nm, the initial magnetization curve becomes flat. The evolution of initial magnetization curves with film thickness can be understood by the microstructure of the films. Films with thickness of 15 nm show close-packed grains without any intergranular phases. Such microstructures lead to steep initial magnetization curves. On the other hand, when the film thickness decreased to 3 nm, the film thickness became nonuniform. Such microstructure leads to flat initial magnetization curves.

Oxygen permeability of nanocomposite-based polyolefin films; Permeabilidade do oxigenio em filmes nanocompositos poliolefinicos

Energy Technology Data Exchange (ETDEWEB)

Fujiyama-Novak, Jane H.; Amaral, Rafael A.; Ruffino, Vivianne; Habert, A. Claudio; Borges, Cristiano P., E-mail: jane@peq.coppe.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEQ/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Mano, Barbara [BRASKEM S.A., Duque de Caxias, RJ (Brazil)

2015-07-01

Polyethylene and polypropylene are vastly employed for packaging due to their high versatility and low cost. However, their films are permeable at different degree to small molecules like gases and the use of additives improves the barrier properties. Therefore, the aim of this work is to investigate the effect of organically modified montmorillonite on oxygen transport properties of PE and PP films. Nanocomposites were prepared by means of polymer dissolution in organic solvent and subsequent nanoparticle addition at 3, 5 and 10% (w/w). Scanning electron microscopy images of the films indicate the presence of microcavities and some agglomerated nanoclay. On the other hand, X-rays diffraction analysis shows clay in well-dispersed state independent of polyolefin type. Enhancement of oxygen barrier is achieved, but this property is dependent on the nanoclay content, polyolefin type and film morphology. (author)

The Effect of External Magnetic Field on Dielectric Permeability of Multiphase Ferrofluids

Science.gov (United States)

Dotsenko, O. A.; Pavlova, A. A.; Dotsenko, V. S.

2018-03-01

Nowadays, ferrofluids are applied in various fields of science and technology, namely space, medicine, geology, biology, automobile production, etc. In order to investigate the feasibility of applying ferrofluids in magnetic field sensors, the paper presents research into the influence of the external magnetic field on dielectric permeability of ferrofluids comprising magnetite nanopowder, multiwall carbon nanotubes, propanetriol and deionized water. The real and imaginary parts of the dielectric permeability change respectively by 3.7 and 0.5% when applying the magnetic field parallel to the electric. The findings suggest that the considered ferrofluid can be used as a magnetic level gauge or in design of variable capacitors.

Magnetic induction measurements and identification of the permeability of Magneto-Rheological Elastomers using finite element simulations

International Nuclear Information System (INIS)

Schubert, Gerlind; Harrison, Philip

2016-01-01

The isotropic and anisotropic magnetic permeability of Magneto-Rheological Elastomers (MREs) is identified using a simple inverse modelling approach. This involves measuring the magnetic flux density and attractive force occurring between magnets, when MRE specimens are placed in between the magnets. Tests were conducted using isotropic MREs with 10–40% and for anisotropic MREs with 10–30%, particle volume concentration. Magnetic permeabilities were then identified through inverse modelling, by simulating the system using commercially available multi-physics finite element software. As expected, the effective permeability of isotropic MREs was found to be scalar-valued; increasing with increasing particle volume concentration (from about 1.6 at 10% to 3.7 at 30% particle volume concentration). The magnetic permeability of transversely isotropic MRE was itself found to be transversely isotropic, with permeabilities in the direction of particle chain alignment from 1.6 at 10% to 4.45 at 30%, which is up to 1.07–1.25 times higher than in the transverse directions. Results of this investigation are demonstrated to show good agreement with those reported in the literature. - Highlights: • An inverse modelling approach for permeability identification of MREs. • Comparison of magnetic flux measurements with finite element simulations. • Permeability of isotropic and anisotropic MREs of varying iron content identified. • Results compare favourably with theoretical predictions. • Simple experimental setup. • Inexpensive technique that can be conducted in most mechanical test labs.

Complementary analyses of hollow cylindrical unioriented permanent magnet (HCM) with high permeability external layer

Science.gov (United States)

Lobo, Carlos M. S.; Tosin, Giancarlo; Baader, Johann E.; Colnago, Luiz A.

2017-10-01

In this article, several studies based on analytical expressions and computational simulations on Hollow Cylindrical Magnets with an external soft ferromagnetic material (HCM magnets) are presented. Electromagnetic configurations, as well as permanent-magnet-based structures, are studied in terms of magnetic field strength and homogeneity. Permanent-magnet-based structures are further analyzed in terms of the anisotropy of the magnetic permeability. It was found that the HCM magnets produce a highly homogeneous magnetic field as long as the magnetic material is isotropic. The dependency of the magnetic field strength and homogeneity in terms of the anisotropy of the magnetic permeability is also explored here. These magnets can potentially be used in medium-resolution NMR spectrometers and high-field NMR spectrometers.

Permeability coefficient of proton irradiated polyethylene terephatalate thin films

International Nuclear Information System (INIS)

Bassani, L.C.; Santos, W.M.S.; Marechal, B.

1983-01-01

The principle of operation of an apparatus developed to study gas permation through thin films is described and the measurement method is discussed. Use is made of diffusion theory to obtain a expression for the permeability coefficient as a function of the rate of increase of the pressure in the receiving volume. The Gibbs function for permeation of Helium through Polyethylene Terephtalate (P.E.T.) is determined. The permeability coefficient of Helium is found to increase significantly with the range of the implanted protons although the incident charge has been kept constant. The hypothesis of structural modifications of the proton implanted P.E.T. seems to be confirmed by small angles X-rays scattering experiments on the irradiated samples. (Author) [pt

Soft Magnetic Properties of Nanocrystalline Fe-M-(B and/or O)(M=Group IV A, V A Elements) Alloy Films

OpenAIRE

Hayakawa, Y.; Makino, A.; Inoue, A.; Masumoto, T.

1996-01-01

In Fe-M-(B and/or O)(M=group IV A, V A elements) alloy films, nanocrystalline bcc phase are formed by annealing the amorphous single phase for Fe-M-B films, whereas the bcc nanocrystals are already formed in an as-deposited state for Fe-M-O or Fe-M-B-O) films. Among Fe-M-B films with various M elements, Fe-(Zr, Hf, Nb, Ta)-B alloy films exhibit high saturation magnetization (Is) above 1.4 T and high relative permeability (|μ|) above 1000 at 1MHz. The highest |μ| of 3460 at 1MHz is obtained fo...

Complementary analyses of hollow cylindrical unioriented permanent magnet (HCM) with high permeability external layer.

Science.gov (United States)

Lobo, Carlos M S; Tosin, Giancarlo; Baader, Johann E; Colnago, Luiz A

2017-10-01

In this article, several studies based on analytical expressions and computational simulations on Hollow Cylindrical Magnets with an external soft ferromagnetic material (HCM magnets) are presented. Electromagnetic configurations, as well as permanent-magnet-based structures, are studied in terms of magnetic field strength and homogeneity. Permanent-magnet-based structures are further analyzed in terms of the anisotropy of the magnetic permeability. It was found that the HCM magnets produce a highly homogeneous magnetic field as long as the magnetic material is isotropic. The dependency of the magnetic field strength and homogeneity in terms of the anisotropy of the magnetic permeability is also explored here. These magnets can potentially be used in medium-resolution NMR spectrometers and high-field NMR spectrometers. Copyright © 2017 Elsevier Inc. All rights reserved.

Magnetic anisotropies and magnetic switching in Co films

Science.gov (United States)

Bland, J. A. C.; Baird, M. J.; Leung, H. T.; Ives, A. J. R.; Mackay, K. D.; Hughes, H. P.

1992-07-01

We have used the magneto-optical Kerr effect to investigate the role of the substrate and growth conditions in determining the magnetic switching behaviour of Co films in the thickness range 100-200 Å supported by GaAs(001) and Si(111) substrates. We discuss the anisotropic magnetic hysteresis behaviour observed for Co/GaAs and Co/Si films in terms of coherent rotation of the magnetisation vector during magnetic switching. Equivalent films supported by glass substrates are found to be almost isotropic in-plane. The in-plane coercive and saturation fields are observed to lie in the range 20-80 Oe but perpendicular saturation fields of 25 and 19 kOe are found for the Co/Si and Co/GaAs systems respectively which substantially exceed the demagnetising field in each case. The measured perpendicular anisotropy fields differ strongly from the values for hcp and bcc Co and are attributed to the details of the interface and film structure. We also report strongly frequency dependent magnetic switching behaviour in these Co films.

Cage and linear structured polysiloxane/epoxy hybrids for coatings: Surface property and film permeability.

Science.gov (United States)

Ma, Yanli; He, Ling; Jia, Mengjun; Zhao, Lingru; Zuo, Yanyan; Hu, Pingan

2017-08-15

Three polysiloxane/epoxy hybrids obtained by evolving cage- or linear-structured polysiloxane into poly glycidyl methacrylate (PGMA) matrix are compared used as coatings. One is the cage-structured hybrid of P(GMA/MA-POSS) copolymer obtained by GMA and methacrylisobutyl polyhedral oligomeric silsesquioxane (MA-POSS) via free radical polymerization, the other two are PGMA/NH 2 -POSS and PGMA/NH 2 -PDMS hybrids by cage-structured aminopropyllsobutyl POSS (NH 2 -POSS) or linear-structured diamino terminated poly(dimethylsiloxane) (NH 2 -PDMS) to cure PGMA. The effect of MA-POSS, NH 2 -POSS and NH 2 -PDMS on polysiloxane/epoxy hybrid films is characterized according to their surface morphology, transparency, permeability, adhesive strength and thermo-mechanical properties. Due to caged POSS tending to agglomerate onto the film surface, P(GMA/MA-POSS) and PGMA/NH 2 -POSS films exhibit much more heterogeneous surfaces than PGMA/NH 2 -PDMS film, but the well-compatibility between epoxy matrix and MA-POSS has provided P(GMA/MA-POSS) film with much higher transmittance (98%) than PGMA/NH 2 -POSS film (24%), PGMA/NH 2 -PDMS film (27%) and traditional epoxy resin film (5%). The introduction of polysiloxane into epoxy matrix is confirmed to create hybrids with strong adhesive strength (526-1113N) and high thermos-stability (T g =262-282°C), especially the cage-structured P(GMA/MA-POSS) hybrid (1113N and 282°C), but the flexible PDMS improves PGMA/NH 2 -PDMS hybrid with much higher storage modulus (519MPa) than PGMA/NH 2 -POSS (271MPa), which suggests that PDMS is advantage in improving the film stiffness than POSS cages. However, cage-structured P(GMA/MA-POSS) and PGMA/NH 2 -POSS indicate higher permeability than PGMA/NH 2 -PDMS and traditional epoxy resin. Comparatively, the cage-structured P(GMA/MA-POSS) hybrid is the best coating in transparency, permeability, adhesive strength and thermostability, but linear-structured PGMA/NH 2 -PDMS hybrid behaviors the best coating in

High-frequency parameters of magnetic films showing magnetization dispersion

International Nuclear Information System (INIS)

Sidorenkov, V.V.; Zimin, A.B.; Kornev, Yu.V.

1988-01-01

Magnetization dispersion leads to skewed resonance curves shifted towards higher magnetizing fields, together with considerable reduction in the resonant absorption, while the FMR line width is considerably increased. These effects increase considerably with frequency, in contrast to films showing magnetic-anisotropy dispersion, where they decrease. It is concluded that there may be anomalies in the frequency dependence of the resonance parameters for polycrystalline magnetic films

Classification of cassava starch films by physicochemical properties and water vapor permeability quantification by FTIR and PLS.

Science.gov (United States)

Henrique, C M; Teófilo, R F; Sabino, L; Ferreira, M M C; Cereda, M P

2007-05-01

Cassava starches are widely used in the production of biodegradable films, but their resistance to humidity migration is very low. In this work, commercial cassava starch films were studied and classified according to their physicochemical properties. A nondestructive method for water vapor permeability determination, which combines with infrared spectroscopy and multivariate calibration, is also presented. The following commercial cassava starches were studied: pregelatinized (amidomax 3550), carboxymethylated starch (CMA) of low and high viscosities, and esterified starches. To make the films, 2 different starch concentrations were evaluated, consisting of water suspensions with 3% and 5% starch. The filmogenic solutions were dried and characterized for their thickness, grammage, water vapor permeability, water activity, tensile strength (deformation force), water solubility, and puncture strength (deformation). The minimum thicknesses were 0.5 to 0.6 mm in pregelatinized starch films. The results were treated by means of the following chemometric methods: principal component analysis (PCA) and partial least squares (PLS) regression. PCA analysis on the physicochemical properties of the films showed that the differences in concentration of the dried material (3% and 5% starch) and also in the type of starch modification were mainly related to the following properties: permeability, solubility, and thickness. IR spectra collected in the region of 4000 to 600 cm(-1) were used to build a PLS model with good predictive power for water vapor permeability determination, with mean relative errors of 10.0% for cross-validation and 7.8% for the prediction set.

Effects of discontinuous magnetic permeability on magnetodynamic problems

KAUST Repository

Guermond, J.-L.

2011-07-01

A novel approximation technique using Lagrange finite elements is proposed to solve magneto-dynamics problems involving discontinuous magnetic permeability and non-smooth interfaces. The algorithm is validated on benchmark problems and is used for kinematic studies of the Cadarache von Kármán Sodium 2 (VKS2) experimental fluid dynamo. © 2011 Elsevier Inc.

Demonstrations of Magnetic Phenomena: Measuring the Air Permeability Using Tablets

Science.gov (United States)

Lara, V. O. M.; Amaral, D. F.; Faria, D.; Vieira, L. P.

2014-01-01

We use a tablet to experimentally determine the dependencies of the magnetic field (B) on the electrical current and the axial distance from a coil (z). Our data shows good precision on the inverse cubic dependence of the magnetic field on the axial distance, B?z[superscript -3]. We obtain the value of air permeability µ[subscript air] with good…

Method and Apparatus for High-Permeability Magnetostrictive/Piezo-Fiber Laminates Having Colossal, Near-Ideal Magnetoelectricity

OpenAIRE

2007-01-01

An ME composite laminate of at least one (1-3) piezo-fiber layer coupled with high-permeability alloy magnetostrictive layers, optionally formed of FeBSiC or equivalent. The composite laminate alternates the (1-3) piezo-fiber and high-permeability alloy magnetostrictive layers in a stacked manner. Optionally, the magnetization direction of the high-permeability alloy magnetostrictive layers and polarization direction of the piezo-fiber layer are an (L-L) arrangement. Optionally, thin film pol...

Magnetic anisotropies in ultrathin bismuth iron garnet films

International Nuclear Information System (INIS)

Popova, Elena; Franco Galeano, Andres Felipe; Deb, Marwan; Warot-Fonrose, Bénédicte; Kachkachi, Hamid; Gendron, François; Ott, Frédéric

2013-01-01

Ultrathin bismuth iron garnet Bi 3 Fe 5 O 12 films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi 3 Fe 5 O 12 films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi 3 Fe 5 O 12 films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi 3 Fe 5 O 12 were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed

Magnetic anisotropies in ultrathin bismuth iron garnet films

Energy Technology Data Exchange (ETDEWEB)

Popova, Elena, E-mail: popova@physique.uvsq.fr [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Franco Galeano, Andres Felipe [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Deb, Marwan [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Warot-Fonrose, Bénédicte [Centre d' Elaboration de Matériaux et d' Etudes Structurales (CEMES), CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS–Universidad de Zaragoza (Spain); Kachkachi, Hamid [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Gendron, François [Institut des NanoSciences de Paris (INSP), CNRS/Université Pierre et Marie Curie-Paris 6, 4 place Jussieu, Boîte courrier 840, 75252 Paris Cedex 05 (France); Ott, Frédéric [Laboratoire Léon Brillouin (LLB), CNRS/CEA, Bâtiment 563, CEA Saclay, 91191 Gif sur Yvette Cedex (France); and others

2013-06-15

Ultrathin bismuth iron garnet Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi{sub 3}Fe{sub 5}O{sub 12} films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi{sub 3}Fe{sub 5}O{sub 12} were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed.

Magnetic permeability of stainless steel for use in accelerator beam transport systems

International Nuclear Information System (INIS)

Wilson, N.G.; Bunch, P.

1991-01-01

High-vacuum beam transport tubes are being designed for use in an accelerator under development at Los Alamos. In areas such as weld-heat-affected zones, the tubes will require localized magnetic permeability of less than 1.02. Seven austenitic stainless steel candidates, 304L, 310, 316L, 317LN, 20Cb-3, Nitronic 33, and Nitronic 40, have been evaluated to determine their permeability in cold-worked, annealed, and weld-affected zones. 310 and 20Cb-3 showed permeability after welding of less than 1.01. 1 ref., 1 fig., 1 tab

Flexible magnetic thin films and devices

Science.gov (United States)

Sheng, Ping; Wang, Baomin; Li, Runwei

2018-01-01

Flexible electronic devices are highly attractive for a variety of applications such as flexible circuit boards, solar cells, paper-like displays, and sensitive skin, due to their stretchable, biocompatible, light-weight, portable, and low cost properties. Due to magnetic devices being important parts of electronic devices, it is essential to study the magnetic properties of magnetic thin films and devices fabricated on flexible substrates. In this review, we mainly introduce the recent progress in flexible magnetic thin films and devices, including the study on the stress-dependent magnetic properties of magnetic thin films and devices, and controlling the properties of flexible magnetic films by stress-related multi-fields, and the design and fabrication of flexible magnetic devices. Project supported by the National Key R&D Program of China (No. 2016YFA0201102), the National Natural Science Foundation of China (Nos. 51571208, 51301191, 51525103, 11274321, 11474295, 51401230), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No. 2016270), the Key Research Program of the Chinese Academy of Sciences (No. KJZD-EW-M05), the Ningbo Major Project for Science and Technology (No. 2014B11011), the Ningbo Science and Technology Innovation Team (No. 2015B11001), and the Ningbo Natural Science Foundation (No. 2015A610110).

Dependence of magnetic permeability on residual stresses in alloyed steels

Directory of Open Access Journals (Sweden)

E. Hristoforou

2018-04-01

Full Text Available A method for the monitoring of residual stress distribution in steels has been developed based on non-destructive surface magnetic permeability measurements. In order to investigate the potential utilization of the magnetic method in evaluating residual stresses, the magnetic calibration curves of various ferromagnetic alloyed steels’ grade (AISI 4140, TRIP and Duplex were examined. X-Ray diffraction technique was used for determining surface residual stress values. The overall measurement results have shown that the residual stress determined by the magnetic method was in good agreement with the diffraction results. Further experimental investigations are required to validate the preliminary results and to verify the presence of a unique normalized magnetic stress calibration curve.

Dependence of magnetic permeability on residual stresses in alloyed steels

Science.gov (United States)

Hristoforou, E.; Ktena, A.; Vourna, P.; Argiris, K.

2018-04-01

A method for the monitoring of residual stress distribution in steels has been developed based on non-destructive surface magnetic permeability measurements. In order to investigate the potential utilization of the magnetic method in evaluating residual stresses, the magnetic calibration curves of various ferromagnetic alloyed steels' grade (AISI 4140, TRIP and Duplex) were examined. X-Ray diffraction technique was used for determining surface residual stress values. The overall measurement results have shown that the residual stress determined by the magnetic method was in good agreement with the diffraction results. Further experimental investigations are required to validate the preliminary results and to verify the presence of a unique normalized magnetic stress calibration curve.

A new non-destructive method for estimating the remanent life of a turbine rotor steel by reversible magnetic permeability

International Nuclear Information System (INIS)

Ryu, K.S.; Nahm, S.H.; Park, J.S.; Yu, K.M.; Kim, Y.B.; Son, D.

2002-01-01

We present a new magnetic and non-destructive procedure to evaluate the remanent life of 1Cr-1Mo-0.25V steel using the value of reversible magnetic permeability. The method is based on the existence of reversible magnetic permeability in the differential magnetization around the coercive force. The measurement principle is based on the foundation harmonics voltage induced in a coil using a lock-in amplifier tuned to a frequency of the exciting one. Results obtained for reversible magnetic permeability and Vickers hardness on the aged sample show that the peak interval of reversible magnetic permeability (PIRMP) and Vickers hardness decreases as aging time increases. A softening curve is obtained from the correlation between Vickers hardness and the PIRMP. This curve can be used as a non-destructive method to evaluate the remanent life of 1Cr-1Mo-0.25V steel

Determination of magnetic properties of multilayer metallic thin films

International Nuclear Information System (INIS)

Birlikseven, C.

2000-01-01

In recent year, Giant Magnetoresistance Effect has been attracting an increasingly high interest. High sensitivity magnetic field detectors and high sensitivity read heads of magnetic media can be named as important applications of these films. In this work, magnetic and electrical properties of single layer and thin films were investigated. Multilayer thin films were supplied by Prof. Dr. A. Riza Koeymen from Texas University. Multilayer magnetic thin films are used especially for magnetic reading and magnetic writing. storing of large amount of information into small areas become possible with this technology. Single layer films were prepared using the electron beam evaporation technique. For the exact determination of film thicknesses, a careful calibration of the thicknesses was made. Magnetic properties of the multilayer films were studied using the magnetization, magnetoresistance measurements and ferromagnetic resonance technique. Besides, by fitting the experimental results to the theoretical models, effective magnetization and angles between the ferromagnetic layers were calculated. The correspondence between magnetization and magnetoresistance was evaluated. To see the effect of anisotropic magnetoresistance in the magnetoresistance measurements, a new experimental set-up was build and measurements were taken in this set-up. A series of soft permalloy thin films were made, and temperature dependent resistivity, magnetoresistance, anisotropic magnetoresistance and magnetization measurements were taken

Magnetic characterisation of longitudinal thin film media

International Nuclear Information System (INIS)

Dova, P.

1998-09-01

Magnetic characterisation techniques, as applied to longitudinal thin film media, have been investigated. These included the study of the differentials of the remanence curves, the delta-M plot and the examination of the critical volumes. Several thin film structures, which are currently used or are being considered for future media applications, have been examined using these techniques. Most of the films were Co-alloys with the exception of a set of Barium ferrite films. Both monolayer and multilayer structures were studied. It was found that the study of activation volumes provides a better insight into the reversal mechanisms of magnetic media, especially in the case of complex structures such as multilayer films and films with bicrystal microstructure. Furthermore, an evaluation study of different methods of determining critical volumes showed that the method using time dependence measurements and the micromagnetic approach is the most appropriate. The magnetic characteristics of the thin film media under investigation were correlated with their microstructure and, where possible, with their noise performance. Magnetic force microscopy was also used for acquiring quasi-domain images in the ac-demagnetised state. It was found that in all Co-alloy films the dominant intergranular coupling is magnetising in nature, the level of which is governed by the Cr content in the magnetic layer. In the case of laminated media it was found that when non-magnetic spacers are used, the nature of the interlayer coupling depends on the spacer thickness. In double layer structures with no spacer, the top layer replicates the crystallographic texture of the bottom layer, and the overall film properties are a combination of the two layers. In bicrystal films the coupling is determined by the Cr segregation in the grain boundaries. Furthermore, the presence of stacking faults in bicrystal films deteriorates their thermal stability, but can be prevented by improving the epitaxial

Magnetic field extraction of trap-based electron beams using a high-permeability grid

International Nuclear Information System (INIS)

Hurst, N. C.; Danielson, J. R.; Surko, C. M.

2015-01-01

A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described

Tailoring the magnetic properties and thermal stability of FeSiAl-Al{sub 2}O{sub 3} thin films fabricated by hybrid oblique gradient-composition sputtering

Energy Technology Data Exchange (ETDEWEB)

Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China); Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, 117411 Singapore (Singapore); Soh, Wee Tee [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive3, 117542 Singapore (Singapore); Ong, C.K. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, 117411 Singapore (Singapore); Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive3, 117542 Singapore (Singapore); Peng, Long; Li, Lezhong [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

2017-05-01

In this study, we systematically investigate the dynamic magnetic properties of FeSiAl-Al{sub 2}O{sub 3} thin films fabricated by hybrid oblique gradient-composition sputtering technique with respect to temperature ranging from 300 K to 420 K. The magnetic anisotropy field H{sub K} and ferromagnetic resonance frequency f{sub FMR} can be tuned from 14.06 to 110.18 Oe and 1.05–3.05 GHz respectively, by changing the oblique angle, which can be interpreted in terms of the contribution of stress-induced anisotropy and shape anisotropy. In addition, the thermal stability of FeSiAl-Al{sub 2}O{sub 3} films in terms of magnetic anisotropy H{sub K} and ferromagnetic resonance frequency f{sub FMR} are enhanced with the increase of oblique angle up to 35° while the thermal stability of effective Gilbert damping factor α{sub eff} and the maximum imaginary permeability μ’’{sub max} are improved with the increase of oblique angle up to 45°. - Highlights: • We prepared FeSiAl-based thin films using hybrid oblique gradient-composition deposition technique. • The microwave properties of FeSiAl-based thin films were systematically studied. • The thermal stability of microwave properties of FeSiAl-based films was studied. • The permeabilities were got using shorted micro-strip transmission-line perturbation. • The thermal stability of properties we studied is relatively good.

Magnetic after-effect in manganite films

International Nuclear Information System (INIS)

Sirena, M.; Steren, L.B.; Guimpel, J.

2001-01-01

The time dependence of the magnetic and transport properties on La 0.6 Sr 0.4 MnO 3 films and bulk samples has been studied through magnetization and resistivity measurements. A magnetic after-effect has been observed in all samples. At low temperatures, the low-field magnetization, can be described by the function M(t)=M c +M d exp(-t/τ)+S(H,T)ln(t). The resistivity increases logarithmically in the same temperature range, indicating the evolution of the sample to a more disordered state. Above a characteristic temperature, this behaviour is reversed and an increase of the magnetization with time is observed. The relaxation parameters depend on the bulk or films character of the samples. In the latter case, a dependence on the film thickness was found. A direct correlation between the time dependence of the resistivity and magnetization curves in manganite compounds was found

Magnetic anisotropies in SmCo thin films

International Nuclear Information System (INIS)

Chen, K.

1993-01-01

A systemic study of the deposition processes and magnetic properties for the Sm-Co film system has been carried out. Films of Sm-Co system with various magnetic anisotropies have been synthesized through sputter deposition in both crystalline and amorphous phases. The origins of various anisotropies have been studied. Thermalized sputter deposition process control was used to synthesize Fe enriched Sm-Co films with rhombohedral Th 2 Zn 17 type structure. The film exhibited unusually strong textures with the crystallographic c axes of the crystallites aligned in the film plane. A large anisotropy was resulted with easy axis in the film plane. A well defined and large in-the-film-plane anisotropy of exceptionally high value of 3.3 x 10 6 erg/cm 3 has been obtained in the amorphous SmCo films by applying a magnetic field in the film plane during deposition. It was found that the in-the-film-plane anisotropy depended essentially on the applied field and Sm concentration. For films not synthesized through thermallized sputtering, the easy axis of the film could reoriented. A perpendicular anisotropy was also presented in the film synthesized through thermallized sputtering deposition. A large in-plane anisotropy was obtained in films deposited above ambient temperatures. It was concluded that the surface induced short range ordering was the origin of the in-the-film-phase anisotropy observed in amorphous film deposited in the presence of a magnetic field. The formation mechanism was different from that of the short range ordering induced by field annealing. The perpendicular anisotropy was shown to be growth induced. Large in-plane anisotropy in amorphous films was resulted form partial crystallization in the film. Both the formation of growth induced structure and partial crystallization in the film prevented the formation of the pair ordering and decreased in-the-film-plane anisotropy

Magnetic domains in Ni-Mn-Ga martensitic thin films

International Nuclear Information System (INIS)

Chernenko, V A; Anton, R Lopez; Kohl, M; Ohtsuka, M; Orue, I; Barandiaran, J M

2005-01-01

A series of martensitic Ni 52 Mn 24 Ga 24 thin films deposited on alumina ceramic substrates has been prepared by using RF(radio-frequency) magnetron sputtering. The film thickness, d, varies from 0.1 to 5.0m. Magnetic domain patterns have been imaged by the MFM (magnetic force microscopy) technique. A maze domain structure is found for all studied films. MFM shows a large out-of-plane magnetization component and a rather uniform domain width for each film thickness. The domain width, δ, depends on the film thickness as δ∝√d in the whole studied range of film thickness. This dependence is the expected one for magnetic anisotropy and magnetostatic contributions in a perpendicular magnetic domain configuration. The proportionality coefficient is also consistent with the values of saturation magnetization and magnetic anisotropy determined in the samples

Magnetic after-effect in manganite films

Energy Technology Data Exchange (ETDEWEB)

Sirena, M. E-mail: sirenam@ib.cnea.gov.ar; Steren, L.B.; Guimpel, J

2001-05-01

The time dependence of the magnetic and transport properties on La{sub 0.6}Sr{sub 0.4}MnO{sub 3} films and bulk samples has been studied through magnetization and resistivity measurements. A magnetic after-effect has been observed in all samples. At low temperatures, the low-field magnetization, can be described by the function M(t)=M{sub c}+M{sub d} exp(-t/{tau})+S(H,T)ln(t). The resistivity increases logarithmically in the same temperature range, indicating the evolution of the sample to a more disordered state. Above a characteristic temperature, this behaviour is reversed and an increase of the magnetization with time is observed. The relaxation parameters depend on the bulk or films character of the samples. In the latter case, a dependence on the film thickness was found. A direct correlation between the time dependence of the resistivity and magnetization curves in manganite compounds was found.

Upper critical magnetic field of superconducting films with magnetic impurities

International Nuclear Information System (INIS)

Lemberger, T.R.

1978-01-01

The upper critical magnetic field, H/sub c2/(T), of In-Mn and Pb-Mn alloy films was measured. H/sub c2/ was determined from the resistance of the films. The results were compared with the theory of Fulde and Maki. This theory assumes that the electron-phonon coupling is weak, and that the interaction between the impurity spins and the conduction electron spins is weak. The theory predicts that the pair-breaking effect of the magnetic impurities is temperature-independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. Furthermore, it predicts explicitly the temperature dependence of H/sub c2/. The temperature dependence of H/sub c2/ for the In-Mn alloy films is well described by the Fulde-Maki theory, despite the moderately strong electron-phonon coupling and the strong interaction between the impurity spins and the conduction electron spins. The temperature dependence of H/sub c2/ for the Pb-Mn alloy films is not well described by the Fulde-Maki theory, probably due to the strong electron-phonon coupling in Pb. However, even without a quantitatively correct theory, one can conclude from the Pb-Mn data that the pair-breaking effect of the magnetic impurities is temperature independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. For some of the Pb-Mn alloy films, there was a region of positive curvature in H/sub c2/(T) near the zero-field transition temperature. This positive curvature is not understood

Magnetic neutron diffraction of MnO thin films

International Nuclear Information System (INIS)

Neubeck, W.; Vettier, C.; Mannix, D.; Bernhoeft, N.; Hiess, A.; Ranno, L.; Givord, D.

1999-01-01

We report on magnetic neutron diffraction carried out on various epitaxial MnO(III) thin films grown on sapphire and MgO substrates. In all samples, of masses between 5 and 50 μg, magnetic Bragg peaks have been observed. The films exhibit what appears to be continuous phase-transitions in contrast to the strongly discontinuous transition exhibited by bulk samples. In addition, the Neel temperature of films prepared on sapphire substrates is strongly enhanced above that of the bulk whilst that of the film grown on MgO is depressed. The possibility to measure magnetic excitations in such thin film systems is discussed in the light of promising test results obtained from an inelastic magnetic neutron scattering experiment on the IN8 spectrometer. (authors)

Implant-assisted magnetic drug targeting in permeable microvessels: Comparison of two-fluid statistical transport model with experiment

Energy Technology Data Exchange (ETDEWEB)

ChiBin, Zhang; XiaoHui, Lin, E-mail: lxh60@seu.edu.cn; ZhaoMin, Wang; ChangBao, Wang

2017-03-15

In experiments and theoretical analyses, this study examines the capture efficiency (CE) of magnetic drug carrier particles (MDCPs) for implant-assisted magnetic drug targeting (IA-MDT) in microvessels. It also proposes a three-dimensional statistical transport model of MDCPs for IA-MDT in permeable microvessels, which describes blood flow by the two-fluid (Casson and Newtonian) model. The model accounts for the permeable effect of the microvessel wall and the coupling effect between the blood flow and tissue fluid flow. The MDCPs move randomly through the microvessel, and their transport state is described by the Boltzmann equation. The regulated changes and factors affecting the CE of the MDCPs in the assisted magnetic targeting were obtained by solving the theoretical model and by experimental testing. The CE was negatively correlated with the blood flow velocity, and positively correlated with the external magnetic field intensity and microvessel permeability. The predicted CEs of the MDCPs were consistent with the experimental results. Additionally, under the same external magnetic field, the predicted CE was 5–8% higher in the IA-MDT model than in the model ignoring the permeability effect of the microvessel wall. - Highlights: • A model of MDCPs for IA-MDT in permeable microvessels was established. • An experimental device was established, the CE of MDCPs was measured. • The predicted CE of MDCPs was 5–8% higher in the IA-MDT model.

Nanosphere lithography applied to magnetic thin films

Science.gov (United States)

Gleason, Russell

Magnetic nanostructures have widespread applications in many areas of physics and engineering, and nanosphere lithography has recently emerged as promising tool for the fabrication of such nanostructures. The goal of this research is to explore the magnetic properties of a thin film of ferromagnetic material deposited onto a hexagonally close-packed monolayer array of polystyrene nanospheres, and how they differ from the magnetic properties of a typical flat thin film. The first portion of this research focuses on determining the optimum conditions for depositing a monolayer of nanospheres onto chemically pretreated silicon substrates (via drop-coating) and the subsequent characterization of the deposited nanosphere layer with scanning electron microscopy. Single layers of permalloy (Ni80Fe20) are then deposited on top of the nanosphere array via DC magnetron sputtering, resulting in a thin film array of magnetic nanocaps. The coercivities of the thin films are measured using a home-built magneto-optical Kerr effect (MOKE) system in longitudinal arrangement. MOKE measurements show that for a single layer of permalloy (Py), the coercivity of a thin film deposited onto an array of nanospheres increases compared to that of a flat thin film. In addition, the coercivity increases as the nanosphere size decreases for the same deposited layer. It is postulated that magnetic exchange decoupling between neighboring nanocaps suppresses the propagation of magnetic domain walls, and this pinning of the domain walls is thought to be the primary source of the increase in coercivity.

Effects of eddy current and dispersion of magnetic anisotropy on the high-frequency permeability of Fe-based nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Han, M., E-mail: mangui@gmail.com [State Key Laboratory of Electronic Thin Films & Integrated Devices, University of Electronic Science and Technology of China, Chengdu (China); Rozanov, K.N.; Zezyulina, P.A. [Institute for Theoretical and Applied Electromagnetics, Russian Academy of Sciences, Moscow (Russian Federation); Wu, Yan-Hui [State Key Laboratory of Electronic Thin Films & Integrated Devices, University of Electronic Science and Technology of China, Chengdu (China)

2015-06-01

Fe–Cu–Nb–Si–B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe{sub 3}(Si) with D0{sub 3} superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite. - Highlights: • Hyperfine interactions have been studied for the Fe-based nanocomposites. Please see Fig. 3. • The distribution of magnetic anisotropy has been derived from the initial magnetization curve of the composite. Please see Fig. 6. • The magnetic loss peak has been reconstructed from the measured permeability of composites and from the anisotropy field distribution. Please see Fig. 9.

Effects of eddy current and dispersion of magnetic anisotropy on the high-frequency permeability of Fe-based nanocomposites

International Nuclear Information System (INIS)

Han, M.; Rozanov, K.N.; Zezyulina, P.A.; Wu, Yan-Hui

2015-01-01

Fe–Cu–Nb–Si–B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe 3 (Si) with D0 3 superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite. - Highlights: • Hyperfine interactions have been studied for the Fe-based nanocomposites. Please see Fig. 3. • The distribution of magnetic anisotropy has been derived from the initial magnetization curve of the composite. Please see Fig. 6. • The magnetic loss peak has been reconstructed from the measured permeability of composites and from the anisotropy field distribution. Please see Fig. 9

Influence of Clay Platelet Spacing on Oxygen Permeability of Thin Film Assemblies

Science.gov (United States)

Priolo, Morgan; Gamboa, Daniel; Grunlan, Jaime

2010-03-01

Thin films of anionic natural montmorrilonite clay and various polyelectrolytes have been produced by alternately dipping a plastic substrate into dilute aqueous mixtures containing each ingredient in an effort to show the influence of clay platelet spacing on thin film permeability. After polymer-clay layers have been sequentially deposited, the resulting transparent films exhibit a brick wall nanostructure comprised of completely exfoliated clay bricks in polymeric mortar. This brick wall forms an extremely tortuous path for a molecule to traverse, creating channels perpendicular to the concentration gradient that increase the molecule's diffusion length and delay its transmission. To a first approximation, greater clay spacing (i.e., reduced clay concentration) produces greater oxygen barrier. Oxygen transmission rates below 0.005 cm^3/m^2.day have been achieved for films with only eight clay layers (total thickness of only 200 nm). With optical transparencies greater than 86% and the ability to be microwaved, these thin film composites are good candidates for flexible electronics packaging and foil replacement for food.

The critical properties of magnetic films

International Nuclear Information System (INIS)

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

2010-01-01

Within the framework of the transverse spin-1/2 Ising model and by using the effective field theory with a probability distribution technique that accounts for the self spin correlations, we have studied the critical properties of an L-layer film of simple cubic symmetry in which the exchanges strength are assumed to be different from the bulk values in N S surface layers. We derive and illustrate the expressions for the phase diagrams, order parameter profiles and susceptibility. In such films, the critical temperature can shift to either lower or higher temperature compared with the corresponding bulk value. We calculate also some magnetic properties of the film, such as the layer magnetizations, their averages and their profiles and the longitudinal susceptibility of the film. The film longitudinal susceptibility still diverges at the film critical temperature as does the bulk longitudinal susceptibility.

Simultaneous identification of electric permittivity and magnetic permeability

International Nuclear Information System (INIS)

Feng, Hui; Jiang, Daijun; Zou, Jun

2010-01-01

In this paper we investigate the simultaneous reconstruction of the electric permittivity and magnetic permeability. The two physical parameters are allowed to be highly discontinuous in the concerned physical domain. The ill-posed inverse problem is formulated into an output least-squares nonlinear minimization with BV-regularization. The regularizing effect and mathematical properties of the regularized system are justified and analysed. A fully discrete Nedelec's edge element method is applied to approximate the regularized nonlinear optimization system, and its convergence is demonstrated

Growth and magnetic properties dependence of the Co–Cu/Cu films electrodeposited under high magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Franczak, Agnieszka, E-mail: agnieszka.franczak@mtm.kuleuven.be [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Department of Materials Science (MTM), KU Leuven, Kasteelpark Arenberg 44, 3001 Haverlee (Leuven) (Belgium); Levesque, Alexandra [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Zabinski, Piotr [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Li, Donggang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 314 Box, 110004 Shenyang (China); Czapkiewicz, Maciej [Department of Electronics, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Kowalik, Remigiusz [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Bohr, Frédéric [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); and others

2015-07-15

The present work is focused on the investigations of magnetic properties dependence on microstructure of Co–Cu/Cu films electrodeposited under superimposed high magnetic field. The experimental results indicate a strong effect of an external magnetic field on the morphology of deposited films, more precisely on the Co:Cu ratio that determines the film growth. It is shown that the Co–Cu/Cu films electrodeposited without superimposed magnetic field consisted of two clearly visible features: compact film with incorporated granular particles. Under a superimposed external high magnetic field the privilege growth of the particles was induced. As a consequence, development of the well-defined branched structure of Co–Cu/Cu film was observed. In contrary, the phase compositional investigations do not reveal any changes in the phase formation during electrodeposition under magnetic field conditions. Thus, it is assumed that a strong growth of Co–Cu/Cu films in (111) direction under magnetic or non-magnetic electrodeposition conditions is related with the growth of Cu (111) plane and embedded into it some of the Co fcc atoms of same (111) orientation, as well as the Co hcp atoms that grows in the (002) direction. This non-equilibrium growth of Co–Cu/Cu films under magnetic deposition conditions affects strongly the magnetic properties of deposited films, revealing that films obtained under magnetic fields higher than 3 T were no more magnetic materials. - Highlights: • Co–Cu/Cu electrodeposits were obtained at elevated temperature under HMFs. • The effects of HMFs on microstructure and magnetic properties were investigated. • Interesting morphological changes due to HMFs has been observed. • Changes in Co:Cu ratio due to HMFs modified the magnetic properties of deposits.

Growth and magnetic properties dependence of the Co–Cu/Cu films electrodeposited under high magnetic fields

International Nuclear Information System (INIS)

Franczak, Agnieszka; Levesque, Alexandra; Zabinski, Piotr; Li, Donggang; Czapkiewicz, Maciej; Kowalik, Remigiusz; Bohr, Frédéric

2015-01-01

The present work is focused on the investigations of magnetic properties dependence on microstructure of Co–Cu/Cu films electrodeposited under superimposed high magnetic field. The experimental results indicate a strong effect of an external magnetic field on the morphology of deposited films, more precisely on the Co:Cu ratio that determines the film growth. It is shown that the Co–Cu/Cu films electrodeposited without superimposed magnetic field consisted of two clearly visible features: compact film with incorporated granular particles. Under a superimposed external high magnetic field the privilege growth of the particles was induced. As a consequence, development of the well-defined branched structure of Co–Cu/Cu film was observed. In contrary, the phase compositional investigations do not reveal any changes in the phase formation during electrodeposition under magnetic field conditions. Thus, it is assumed that a strong growth of Co–Cu/Cu films in (111) direction under magnetic or non-magnetic electrodeposition conditions is related with the growth of Cu (111) plane and embedded into it some of the Co fcc atoms of same (111) orientation, as well as the Co hcp atoms that grows in the (002) direction. This non-equilibrium growth of Co–Cu/Cu films under magnetic deposition conditions affects strongly the magnetic properties of deposited films, revealing that films obtained under magnetic fields higher than 3 T were no more magnetic materials. - Highlights: • Co–Cu/Cu electrodeposits were obtained at elevated temperature under HMFs. • The effects of HMFs on microstructure and magnetic properties were investigated. • Interesting morphological changes due to HMFs has been observed. • Changes in Co:Cu ratio due to HMFs modified the magnetic properties of deposits

Effect of temperature and relative humidity on the water vapour permeability and mechanical properties of cassava starch and soy protein concentrate based edible films.

Science.gov (United States)

Chinma, C E; Ariahu, C C; Alakali, J S

2015-04-01

The effect of temperature and relative humidity on the water vapour permeability (WVP) and mechanical properties of cassava starch and soy protein concentrate (SPC) based edible films containing 20 % glycerol level were studied. Tensile strength and elastic modulus of edible films increased with increase in temperature and decreased with increase in relative humidity, while elongation at break decreased. Water vapour permeability of the films increased (2.6-4.3 g.mm/m(2).day.kPa) with increase in temperature and relative humidity. The temperature dependence of water vapour permeation of cassava starch-soy protein concentrate films followed Arrhenius relationship. Activation energy (Ea) of water vapour permeation of cassava starch-soy protein concentrate edible films ranged from 1.9 to 5.3 kJ/mol (R (2)  ≥ 0.93) and increased with increase in SPC addition. The Ea values were lower for the bio-films than for polyvinylidene chloride, polypropylene and polyethylene which are an indication of low water vapour permeability of the developed biofilms compared to those synthetic films.

Film Permeability Determination Using Static Permeability Cells

Science.gov (United States)

The permeability of tarps to soil fumigant pesticides varies depending on the active ingredient chemical: dimethyl disulfide (DMDS), methyl bromide, chloropicrin, or other. The diffusion rate can be represented by the mass transfer coefficient (MTC).

Magnetic surfaces, thin films, and multilayers

International Nuclear Information System (INIS)

Parkin, S.S.P.; Renard, J.P.; Shinjo, T.; Zinn, W.

1992-01-01

This paper details recent developments in the magnetism of surfaces, thin films and multilayers. More than 20 invited contributions and more than 60 contributed papers attest to the great interest and vitality of this subject. In recent years the study of magnetic surfaces, thin films and multilayers has undergone a renaissance, partly motivated by the development of new growth and characterization techniques, but perhaps more so by the discovery of many exciting new properties, some quite unanticipated. These include, most recently, the discovery of enormous values of magnetoresistance in magnetic multilayers far exceeding those found in magnetic single layer films and the discovery of oscillatory interlayer coupling in transition metal multilayers. These experimental studies have motivated much theoretical work. However these developments are to a large extent powered by materials engineering and our ability to control and understand the growth of thin layers just a few atoms thick. The preparation of single crystal thin film layers and multilayers remains important for many studies, in particular, for properties dependent. These studies obviously require engineering not just a layer thicknesses but of lateral dimensions as well. The properties of such structures are already proving to be a great interest

Thickness dependence of magnetization reversal mechanism in perpendicularly magnetized L1{sub 0} FePt films

Energy Technology Data Exchange (ETDEWEB)

Bi, Mei; Wang, Xin, E-mail: xinwang@uestc.edu.cn; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Xie, Jianliang

2017-04-15

We have studied the magnetic switching behavior of L1{sub 0}-ordered FePt films with varying thickness. It was found that coercivity is strongly dependent on the film thickness. The obvious variations of the coercivity in the thin films are confirmed by the measurements of structural and magnetic properties. With increasing thickness, the degree of L1{sub 0} chemical ordering increased, while the magnetization reversal process transforms from a pinned two-steps magnetization reversal to a comparatively smooth domain wall motion behavior. Although considering anisotropy, exchange interaction and applied magnetic field, the switching behavior in films is quite complex, the main features of the magnetization reversal mechanism can be understood by performing detailed investigation on the effect of the deposition temperature and the angle of magnetic field. - Highlights: • Series of FePt films with L1{sub 0} phase have been prepared. • We focused on the magnetization reversal mechanism with varying thicknesses. • The angle-dependence of switching process is revealed in the FePt films. • Different switching mechanisms were found by increasing the film thickness.

Extraordinary Hall-effect in colloidal magnetic nanoparticle films

Energy Technology Data Exchange (ETDEWEB)

Ben Gur, Leah; Tirosh, Einat [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Segal, Amir [School of Physics, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Markovich, Gil, E-mail: gilmar@post.tau.ac.il [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel); Gerber, Alexander, E-mail: gerber@post.tau.ac.il [School of Physics, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801 (Israel)

2017-03-15

Colloidal nickel nanoparticles (NPs) coated with polyvinylpyrrolidone (PVP) were synthesized. The nanoparticle dispersions were deposited on substrates and dried under mild heating to form conductive films. The films exhibited very small coercivity, nearly metallic conductivity, and a significant extraordinary Hall effect signal. This method could be useful for preparing simple, printed magnetic field sensors with the advantage of relatively high sensitivity around zero magnetic field, in contrast to magnetoresistive sensors, which have maximal field sensitivity away from zero magnetic field. - Highlights: • Ni nanoparticle ink capable of forming conductive films on drying. • The Ni nanoparticle films exhibit significant extraordinary Hall effect. • This system could be used for preparing printed magnetic field sensors integrated in 3D printed structures.

Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

Energy Technology Data Exchange (ETDEWEB)

Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim [Institute of Bioelectronics (ICS-8/PGI-8), Forschungszentrum Jülich GmbH, 52425 Jülich (Germany)

2015-04-15

As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

Controlling the competing magnetic anisotropy energies in FineMET amorphous thin films with ultra-soft magnetic properties

Directory of Open Access Journals (Sweden)

Ansar Masood

2017-05-01

Full Text Available Thickness dependent competing magnetic anisotropy energies were investigated to explore the global magnetic behaviours of FineMET amorphous thin films. A dominant perpendicular magnetization component in the as-deposited state of thinner films was observed due to high magnetoelastic anisotropy energy which arises from stresses induced at the substrate-film interface. This perpendicular magnetization component decreases with increasing film thickness. Thermal annealing at elevated temperature revealed a significant influence on the magnetization state of the FineMET thin films and controlled annealing steps leads to ultra-soft magnetic properties, making these thin films alloys ideal for a wide range of applications.

Magnetic domains in Co-cluster assembled films deposited by LECBD

International Nuclear Information System (INIS)

Dumas-Bouchiat, F.; Nagaraja, H.S.; Rossignol, F.; Champeaux, C.; Catherinot, A.

2005-01-01

Cobalt aggregates prepared using a cluster beam generator have been deposited on Si(100) substrate leading to thin films of randomly assembled Co nanoparticles which exhibit a spherical shape with a mono-dispersed diameter distribution centred around 9nm. Films with thickness ranging from 50 to 550nm are investigated using magnetic force microscopy (MFM) and results show the presence of twisted magnetic domains. An in-plane magnetic field applied during the growth of the layer leads to the formation of magnetic stripe domains but we observe a similar behaviour if an in-plane magnetic field is applied after the deposition. This indicates that probably the magnetic field applied during the film growth does not drive its magnetic structure. Finally, the measured variation of magnetic domain width D reveals a t dependence, where t is the film thickness, and is independent of the magnetic history of the films

Growth-related magnetic and physical structures in CMR films

Energy Technology Data Exchange (ETDEWEB)

Hawley, M.E.; Brown, G.W.; Hundley, M.F. [and others

1997-09-01

Scanning tunneling microscopy (STM), atomic force microscopy (AFM), and magnetic force microscopy (MFM) have proven to be powerful tools for revealing property-sensitive structures in magnetic materials. With the renewed interest in perovskite films as materials for read-heads in high density magnetic data storage, the same challenges faced by high temperature superconductor (HTS) film fabrication are repeated for these materials. To begin addressing these challenges, we used vapor phase epitaxy to fabricate La (Sr, Ca,) based manganate films on single crystal perovskite substrates under different conditions and characterized them with scanning probe microscopies, x-ray diffraction, and temperature-dependent magnetization and resistivity measurements (M(T) and {rho}(T)). The as-grown films were polygranular with grain sizes increasing with increasing temperature (T). The post-deposition annealed films consisted of coalesced layers with improved transport properties. The room temperature magnetic structure of the Sr-based films appeared to be related to defects and/or strain.

Magnetic structures in ultra-thin Holmium films: Influence of external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, L.J. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59600-900, RN (Brazil); Departamento de Física, Universidade do Estado do Rio Grande do Norte, Mossoró 59625-620, RN (Brazil); Mello, V.D. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, Mossoró 59625-620, RN (Brazil); Anselmo, D.H.A.L. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59600-900, RN (Brazil); Vasconcelos, M.S., E-mail: mvasconcelos@ect.ufrn.br [Escola de Ciência e Tecnologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil)

2015-03-01

We address the magnetic phases in very thin Ho films at the temperature interval between 20 K and 132 K. We show that slab size, surface effects and magnetic field due to spin ordering impact significantly the magnetic phase diagram. Also we report that there is a relevant reduction of the external field strength required to saturate the magnetization and for ultra-thin films the helical state does not form. We explore the specific heat and the susceptibility as auxiliary tools to discuss the nature of the phase transitions, when in the presence of an external magnetic field and temperature effects. The presence of an external field gives rise to the magnetic phase Fan and the spin-slip structures. - Highlights: • We analyze the magnetic phases of very thin Ho films in the temperature interval 20–132 K. • We show that slab size, etc. due to spin ordering may impact the magnetic phase diagram. • All magnetic phase transitions, for strong magnetic fields, are marked by the specific heat. • The presence of an external field gives rise to the magnetic phase Fan and the spin-slip one.

Electroplated thick-film cobalt platinum permanent magnets

International Nuclear Information System (INIS)

Oniku, Ololade D.; Qi, Bin; Arnold, David P.

2016-01-01

The material and magnetic properties of multi-micron-thick (up to 6 μm) L1 0 CoPt magnetic films electroplated onto silicon substrates are investigated as candidate materials for integration in silicon-based microsystems. The influence of various process conditions on the structure and magnetic properties of electroplated CoPt thick-films is studied in order to better understand the complex process/structure/property relationships associated with the electroplated films. Process variables studied here include different seed layers, electroplating current densities (ranging from 25–200 mA/cm 2 ), deposition times (up to 60 min), and post-deposition annealing times and temperatures. Analyses include film morphology, film thickness, composition, surface roughness, grain size, phase volume fractions, and L1 0 ordering parameter. Key correlations are found relating process and structure variations to the extrinsic magnetic properties (remanence, coercivity, squareness, and energy product). Strong hard magnetic properties (B r ~0.8 T, H ci ~800 kA/m, squareness close to 0.9, and BH max of 100 kJ/m 3 ) are obtained for films deposited on Si/TiN/Ti/Cu at current densities of 100 mA/cm 2 , pH of 7, and subsequently annealed at 675 °C for 30 min. - Highlights: • CoPt films plated up to 6 μm thick on silicon substrates. • A1 to L1 0 phase transformation by annealing in forming gas. • Various process–structure–property relationships explored. • Key results: B r ~0.8 T, H ci ~800 kA/m, squareness 0.9, and BH max ~100 kJ/m 3 .

Magnetic properties of partially oxidized Fe films

Science.gov (United States)

Garcia, Miguel Angel; Lopez-Dominguez, Victor; Hernando, Antonio

Hybrid magnetic nanostructures exhibit appealing properties due to interface and proximity effects. A simple and interesting system of hybrid magnetic nanomaterials are partially oxidized ferromagnetic films. We have fabricated Fe films by thermal evaporation and performed a partial oxidation to magnetite (Fe3O4) by annealing in air at different times and temperatures. The magnetic properties of the films evolve from those of pure metallic iron to pure magnetite, showing intermediate states where the proximity effects control the magnetic behavior. At some stages, the magnetization curves obtained by SQUID and MOKE magnetometry exhibit important differences due to the dissimilar contribution of both phases to the magneto-optical response of the system This work has been supported by the Ministerio Español de Economia y Competitividad (MINECO) MAT2013-48009-C4-1. V.L.D and M.A.G. acknowledges financial support from BBVA foundation.

Uniaxial anisotropy in magnetite thin film-Magnetization studies

International Nuclear Information System (INIS)

Wiechec, A.; Korecki, J.; Handke, B.; Kakol, Z.; Owoc, D.; Antolak, D.A.; Kozlowski, A.

2006-01-01

Magnetization and electrical resistivity measurements have been performed on a stoichiometric single crystalline magnetite Fe 3 O 4 thin film (thickness of ca. 500 nm) MBE deposited on MgO (1 0 0) substrate. The aim of these studies was to check the influence of preparation method and sample form (bulk vs. thin film) on magnetic anisotropy properties in magnetite. The film magnetization along versus applied magnetic field has been determined both in the direction parallel and perpendicular to the film surface, and at temperatures above and below the Verwey transition. We have found, in agreement with published results, that the in-plane field of 10 kOe was not sufficient to saturate the sample. This can be understood if some additional factor, on top of the bulk magnetocrystalline anisotropy, is taken into account

Using a spin torque nano-oscillator to read memory based on the magnetic permeability

International Nuclear Information System (INIS)

Petrie, J R; Wieland, K A; Fischer, G A; Edelstein, A S; Urazhdin, S

2014-01-01

We present an archival memory utilizing a spin torque nano-oscillator (STNO) to read bits of data with different magnetic permeability. Basing a magnetic memory on this intrinsic property rather than remanent magnetization reduces the risk of data corruption. The permeability of the bits is read as changes in an applied probe field near the media. These changes in the probe field are measured by detecting microwave frequency shifts in STNOs. The probe field can be tuned over hundreds of Oe to optimize the reading of the media. Using a 400 Oe probe field, we have measured 2% frequency shifts in a STNO near micrometre-sized bits of (1) lithographically-patterned permalloy lines and (2) laser-crystallized Metglas lines. Data from either media was not corrupted by exposure to fields of 6400 Oe and temperatures of 523 K. (paper)

Using a spin torque nano-oscillator to read memory based on the magnetic permeability

Science.gov (United States)

Petrie, J. R.; Urazhdin, S.; Wieland, K. A.; Fischer, G. A.; Edelstein, A. S.

2014-02-01

We present an archival memory utilizing a spin torque nano-oscillator (STNO) to read bits of data with different magnetic permeability. Basing a magnetic memory on this intrinsic property rather than remanent magnetization reduces the risk of data corruption. The permeability of the bits is read as changes in an applied probe field near the media. These changes in the probe field are measured by detecting microwave frequency shifts in STNOs. The probe field can be tuned over hundreds of Oe to optimize the reading of the media. Using a 400 Oe probe field, we have measured 2% frequency shifts in a STNO near micrometre-sized bits of (1) lithographically-patterned permalloy lines and (2) laser-crystallized Metglas lines. Data from either media was not corrupted by exposure to fields of 6400 Oe and temperatures of 523 K.

2D magnetic texture analysis of Co-Cu films

Energy Technology Data Exchange (ETDEWEB)

Bayirli, Mehmet; Karaagac, Oznur; Kockar, Hakan [Balikesir Univ. (Turkey). Physics Dept.; Alper, Mursel [Uludag Univ., Bursa (Turkey). Physics Dept.

2017-08-01

The magnetic textures for the produced magnetic materials are important concepts in accordance with technical applications. Therefore, the aim of this article is to determine 2D magnetic textures of electrodeposited Co-Cu films by the measurement of hysteresis loops at the incremented angles. For that, Co-Cu films were deposited with different Co{sup 2+} in the electrolyte. In addition, the easy-axis orientation in the films from the squareness values of the angles, M{sub p}(β) obtained by the hysteresis loops have been numerically studied using the Fourier series analysis. The differences observed in the magnetic easy-axis distributions were attributed to changes of the incorporation of Co in the films with the change of Co{sup 2+} in the electrolyte. The coefficients of Fourier series (A{sub 0} and A{sub 2n}) were also computed for 2D films. It is seen that a systematic and small decrease in A{sub 0} and an obvious decrease in A{sub 2n} (n=1) were observed with increasing incorporated Co in the films. Results imply that interactions cause slightly demagnetization effect accordance with higher incorporation of Co in the films. Furthermore, the crystal structure of the Co-Cu films analysed by X-ray diffraction revealed that the films have dominantly face-centred cubic structure. Film contents analysed by energy-dispersive X-ray spectroscopy and film morphologies observed by scanning electron microscope also support the magnetic texture analysis results found by numerical computation.

2D magnetic texture analysis of Co-Cu films

International Nuclear Information System (INIS)

Bayirli, Mehmet; Karaagac, Oznur; Kockar, Hakan; Alper, Mursel

2017-01-01

The magnetic textures for the produced magnetic materials are important concepts in accordance with technical applications. Therefore, the aim of this article is to determine 2D magnetic textures of electrodeposited Co-Cu films by the measurement of hysteresis loops at the incremented angles. For that, Co-Cu films were deposited with different Co"2"+ in the electrolyte. In addition, the easy-axis orientation in the films from the squareness values of the angles, M_p(β) obtained by the hysteresis loops have been numerically studied using the Fourier series analysis. The differences observed in the magnetic easy-axis distributions were attributed to changes of the incorporation of Co in the films with the change of Co"2"+ in the electrolyte. The coefficients of Fourier series (A_0 and A_2_n) were also computed for 2D films. It is seen that a systematic and small decrease in A_0 and an obvious decrease in A_2_n (n=1) were observed with increasing incorporated Co in the films. Results imply that interactions cause slightly demagnetization effect accordance with higher incorporation of Co in the films. Furthermore, the crystal structure of the Co-Cu films analysed by X-ray diffraction revealed that the films have dominantly face-centred cubic structure. Film contents analysed by energy-dispersive X-ray spectroscopy and film morphologies observed by scanning electron microscope also support the magnetic texture analysis results found by numerical computation.

Realizability of metamaterials with prescribed electric permittivity and magnetic permeability tensors

International Nuclear Information System (INIS)

Milton, Graeme W

2010-01-01

We show that any pair of real symmetric tensors ε and μ can be realized as the effective electric permittivity and effective magnetic permeability of a metamaterial at a given fixed frequency. The construction starts with two extremely low-loss metamaterials, with arbitrarily small microstructure, whose existence is ensured by the work of Bouchitte and Bourel and Bouchitte and Schweizer: one having, at the given frequency, a permittivity tensor with exactly one negative eigenvalue, and a positive permeability tensor; and the other having a positive permittivity tensor, and a permeability tensor having exactly one negative eigenvalue. To achieve the desired effective properties, these materials are laminated together in a hierarchical multiple rank laminate structure, with widely separated length scales, and varying directions of lamination, but with the largest length scale still much shorter than the wavelengths and attenuation lengths in the macroscopic effective medium.

Tuning microstructure and magnetic properties of electrodeposited CoNiP films by high magnetic field annealing

Energy Technology Data Exchange (ETDEWEB)

Wu, Chun; Wang, Kai [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Li, Donggang, E-mail: lidonggang@smm.neu.edu.cn [School of Metallurgy, Northeastern University, Shenyang 110819 (China); Lou, Changsheng [School of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110159 (China); Zhao, Yue; Gao, Yang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Wang, Qiang, E-mail: wangq@mail.neu.edu.cn [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China)

2016-10-15

A high magnetic field (up to 12 T) has been used to anneal 2.6-µm-thick Co{sub 50}Ni{sub 40}P{sub 10} films formed by pulse electrodeposition. The effects of high magnetic field annealing on the microstructure and magnetic properties of CoNiP thin films have been investigated. It was found that a high magnetic field accelerated a phase transformation from fcc to hcp and enhanced the preferred hcp-(002) orientation during annealing. Compared with the films annealed without a magnetic field, annealing at 12 T decreased the surface particle size, roughness, and coercivity, but increased the saturation magnetization and remanent magnetization of CoNiP films. The out-of-plane coercivity was higher than that the in-plane for the as-deposited films. After annealing without a magnetic field, the out-of-plane coercivity was equal to that of the in-plane. However, the out-of-plane coercivity was higher than that of the in-plane when annealing at 12 T. These results indicate that high magnetic field annealing is an effective method for tuning the microstructure and magnetic properties of thin films. - Highlights: • High magnetic field annealing accelerated phase transformation from γ to ε. • High magnetic field annealing enhanced preferred hcp-(002) orientation. • High magnetic field annealing decreased particle size, roughness and coercivity. • High magnetic field annealing increased the saturation and remanent magnetization.

Quantum-well-driven magnetism in thin films

DEFF Research Database (Denmark)

Mirbt, S.; Johansson, B.; Skriver, Hans Lomholt

1996-01-01

We have performed local spin-density calculations for an fee (100) Ag substrate covered by 1 to 16 monolayers (ML) of Pd. We find that thin films of Pd are magnetic with a moment of the order of 0.3 mu(B) except for films of 1-2 ML and 5-7 ML where magnetism is completely suppressed. We present...... a physically transparent explanation of this behavior in terms of the Stoner picture and magnetic quantum-well states....

Influence of interdiffusion on the magnetic properties of Co/Si (100) films after high magnetic field annealing

International Nuclear Information System (INIS)

Zhao, Yue; Wang, Kai; Wang, Qiang; Li, Guojian; Lou, Changsheng; Pang, Hongxuan; He, Jicheng

2015-01-01

The influence of interdiffusion on the magnetic properties of Co/Si (100) films after thermal annealing in the presence of a strong magnetic field was investigated. The interdiffusion coefficients of films that were annealed at temperatures of 380 °C and 420 °C in the presence of high magnetic fields were not affected. However, the interdiffusion coefficient of films annealed at 400 °C in the presence of a high magnetic field decreased significantly. The change in the interdiffusion coefficient, caused by high magnetic field annealing, increased the content of the magnetic phase. This increase in the magnetic phase improved the saturation magnetization. A new method of high magnetic field annealing is presented that can modulate the diffusion and magnetic properties of thin films. - Highlights: • Interdiffusion of Co/Si (100) films by high magnetic field annealing was studied. • Thickness of the diffusion layer was reduced by magnetic field annealing at 400 °C. • Interdiffusion coefficient decreased following magnetic field annealing at 400 °C. • Saturation magnetization increased after high magnetic field annealing at 400 °C

Li+-Permeable Film on Lithium Anode for Lithium Sulfur Battery.

Science.gov (United States)

Yang, Yan-Bo; Liu, Yun-Xia; Song, Zhiping; Zhou, Yun-Hong; Zhan, Hui

2017-11-08

Lithium-sulfur (Li-S) battery is an important candidate for next-generation energy storage. However, the reaction between polysulfide and lithium (Li) anode brings poor cycling stability, low Coulombic efficiency, and Li corrosion. Herein, we report a Li protection technology. Li metal was treated in crown ether containing electrolyte, and thus, treated Li was further used as the anode in Li-S cell. Due to the coordination between Li + and crown ether, a Li + -permeable film can be formed on Li, and the film is proved to be able to block the detrimental reaction between Li anode and polysulfide. By using the Li anode pretreated in 2 wt % B15C5-containing electrolyte, Li-S cell exhibits significantly improved cycling stability, such as∼900 mAh g -1 after 100 cycles, and high Coulombic efficiency of>93%. In addition, such effect is also notable when high S loading condition is applied.

Electroplated thick-film cobalt platinum permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Oniku, Ololade D.; Qi, Bin; Arnold, David P., E-mail: darnold@ufl.edu

2016-10-15

The material and magnetic properties of multi-micron-thick (up to 6 μm) L1{sub 0} CoPt magnetic films electroplated onto silicon substrates are investigated as candidate materials for integration in silicon-based microsystems. The influence of various process conditions on the structure and magnetic properties of electroplated CoPt thick-films is studied in order to better understand the complex process/structure/property relationships associated with the electroplated films. Process variables studied here include different seed layers, electroplating current densities (ranging from 25–200 mA/cm{sup 2}), deposition times (up to 60 min), and post-deposition annealing times and temperatures. Analyses include film morphology, film thickness, composition, surface roughness, grain size, phase volume fractions, and L1{sub 0} ordering parameter. Key correlations are found relating process and structure variations to the extrinsic magnetic properties (remanence, coercivity, squareness, and energy product). Strong hard magnetic properties (B{sub r} ~0.8 T, H{sub ci} ~800 kA/m, squareness close to 0.9, and BH{sub max} of 100 kJ/m{sup 3}) are obtained for films deposited on Si/TiN/Ti/Cu at current densities of 100 mA/cm{sup 2}, pH of 7, and subsequently annealed at 675 °C for 30 min. - Highlights: • CoPt films plated up to 6 μm thick on silicon substrates. • A1 to L1{sub 0} phase transformation by annealing in forming gas. • Various process–structure–property relationships explored. • Key results: B{sub r} ~0.8 T, H{sub ci} ~800 kA/m, squareness 0.9, and BH{sub max} ~100 kJ/m{sup 3}.

Structural and magnetic studies of Cr doped nickel ferrite thin films

International Nuclear Information System (INIS)

Panwar, Kalpana; Heda, N. L.; Tiwari, Shailja; Bapna, Komal; Ahuja, B. L.; Choudhary, R. J.; Phase, D. M.

2016-01-01

We have studied the structural and magnetic properties of Cr doped nickel ferrite thin films deposited on Si (100) and Si (111) using pulsed laser deposition technique. The films were deposited under vacuum and substrate temperature was kept at 700°C. X-ray diffraction analysis revealed that films on both substrates have single phase cubic spinel structure. However, the film grown on Si (111) shows better crystalline behavior. Fourier transform infrared spectroscopy suggests that films on both substrates have mixed spinel structure. These films show magnetic hysteresis behavior and magnetization value of film on Si (100) is larger than that on Si (111). It turns out that structural and magnetic properties of these two films are correlated.

Magnetic properties and microwave characteristics of Ni-Zn-Cu ferrite film fabricated by aerosol deposition method

Energy Technology Data Exchange (ETDEWEB)

Kagotani, T. [Departtment of Materials Science, Tohoku University, Aza-Aoba02 Aoba-ku, Sendai 980-8597 (Japan)]. E-mail: kagotant@material.tohoku.ac.jp; Kobayashi, R. [Departtment of Materials Science, Tohoku University, Aza-Aoba02 Aoba-ku, Sendai 980-8597 (Japan); Sugimoto, S. [Departtment of Materials Science, Tohoku University, Aza-Aoba02 Aoba-ku, Sendai 980-8597 (Japan); Inomata, K. [Departtment of Materials Science, Tohoku University, Aza-Aoba02 Aoba-ku, Sendai 980-8597 (Japan); Okayama, K. [Sony EMCS Corporation, Shinagawa INTERCITY C Tower, 2-15-3 Konan, Minato-ku Tokyo 106-6201 (Japan); Akedo, J. [Institute of Advanced Science and Technology, Namiki 1-2-1, Tsukuba 305-8564 (Japan)

2005-04-15

Microwave radiation in the GHz is increasingly being used in telecommunication and data processing. However, this has given rise to electromagnetic wave interference (EMI). Ni-Zn-Cu ferrite film was prepared by aerosol deposition method (ADM) depending on its capability as an absorber or a conducted noise suppressor in the quasi-microwave frequency range. The ADM is a kind of high-speed coating method. The film thickness of 7{mu}m was obtained by the deposition for 4min and the rate was estimated at 2.8{mu}m/min. The saturation magnetization of the film was 6.33x10{sup -5}Wbm/kg and the coercivity was 0.94kA/m. This value was nearly equal to that of sintered sample. The maximum complex permeabilities {mu}' and {mu}'' were 200 and 70. The resonance frequency f{sub r}=200MHz was over Snoek's limit.

Magnetic permeability based diagnostic test for the determination of the canine C-reactive protein concentration in undiluted whole blood

International Nuclear Information System (INIS)

Ibraimi, Filiz; Kriz, Kirstin; Merin, Henrik; Kriz, Dario

2009-01-01

We describe an one-step 11-min magnetic permeability based two-site immunoassay for C-reactive protein (CRP) utilizing polyclonal anti-canine CRP antibody conjugated dextran iron oxide nanoparticles (79 nm) as superparamagnetic labels and polyclonal anti-canine CRP conjugated silica microparticles (15 to 40 μm) as carriers. An inductance based magnetic permeability reader was used to detect the target analyte, CRP, in 10 μL whole blood samples, by measuring the magnetic permeability increase of the silica microparticle sediment due to immuno complex superparamagnetic nanoparticles. Measurements on standards showed a linear response between 0 and 17.5 mg/L CRP. Measurements performed on 16 whole blood samples from mixed breeds showed good correlation with a commercially available ELISA assay.

Ultra-high resistive and anisotropic CoPd–CaF{sub 2} nanogranular soft magnetic films prepared by tandem-sputtering deposition

Energy Technology Data Exchange (ETDEWEB)

Naoe, Masayuki, E-mail: naoe@denjiken.ne.jp [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Kobayashi, Nobukiyo [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Ohnuma, Shigehiro [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan); Iwasa, Tadayoshi; Arai, Ken-Ichi [Research Institute for Electromagnetic Materials, 2-1-1 Yagiyama-Minami, Taihaku-ku, Sendai 982-0807 (Japan); Masumoto, Hiroshi [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578 (Japan)

2015-10-01

Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF{sub 2} matrix, and a specimen having a composition of (Co{sub 0.69}Pd{sub 0.31}){sub 52}–(Ca{sub 0.31}F{sub 0.69}){sub 48} exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau–Lifshitz–Gilbert equation. Furthermore, it was clarified that the CaF{sub 2}-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF{sub 2} matrix. - Highlights: • We fabricated high-resistive and anisotropic granular films by tandem-sputtering. • CaF{sub 2}-based films exhibit a hundredfold higher resistivity than conventional films. • Uniaxial field annealing improved the magnetic properties dramatically. • High uniaxial anisotropy extended ferromagnetic resonance frequency to 4 GHz. • Annealed samples can be regarded as a ferromagnetic homogenized material.

Magnetic structure of Tb-Fe films with an artificially layered structure

International Nuclear Information System (INIS)

Yamauchi, K.; Habu, K.; Sato, N.

1988-01-01

The magnetic structure of Tb-Fe films with an artificially layered structure has been investigated by measuring the temperature dependence of the magnetization of the films. Ferrimagnetic coupling between Tb and Fe through the interface was explicitly observed up to about 9-A Tb and 10-A Fe layers. Films with thinner Tb and Fe layers than these thicknesses are composed of only ferrimagnetically coupled Tb-Fe regions. Films with thicker layers of Tb and Fe are composed of ferrimagnetically coupled Tb-Fe, ferromagnetic Fe, ferromagnetic Tb, and/or magnetically compensated Tb regions. The Tb-Fe films exhibit various temperature dependencies of the magnetization corresponding to these magnetic structures

A new polarized neutrons method for studying depth-inhomogeneously magnetized magnetic films

International Nuclear Information System (INIS)

Korneev, D.A.

1990-01-01

The main specific features of the process of polarized thermal neutrons specular reflection from the surface of depth-inhomogeneously magnetic films are considered theoretically. It is shown how using the method of specular reflection of polarized thermal neutrons from such a films surface, one may restore the depth distribution of the local magnetization vector M-vector(z). 9 refs

Gas permeability and thermal behavior of polypropylene films used for packaging minimally processed fresh-cut potatoes: a case study.

Science.gov (United States)

Siracusa, Valentina; Blanco, Ignazio; Romani, Santina; Tylewicz, Urszula; Dalla Rosa, Marco

2012-10-01

This work reports an experimental study on the permeability and thermal behavior of commercial polypropylene (PP) film used for fresh-cut potatoes packaging. The permeability was tested using oxygen, carbon dioxide, nitrogen, mix of these 3 gases, normally used for modified atmosphere packaging (MAP) and Air, to understand if it would be possible to extend the shelf life of this food product designed for the catering field in respect to the packaging behavior. The temperature influence on permeability data, from 5 to 40 °C, was analyzed, before and after 4, 8, 12, 15, and 20 d of food contact, pointing out the dependence between temperature and gas transmission rate (GTR), solubility (S), diffusion coefficient (D), and time lag (t(L)) parameters. The activation energies (E) of the permeation process were determined with the different gases used in the experiments. The thermal behavior of PP film was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) to well understand its thermal stability. Fourier transformed-infrared with attenuated total reflectance (FT-IR/ATR) spectroscopy was also performed in order to study the influence of the food contact on the chemical characteristics of the polymer film. The results obtained were discussed and compared each other. Studied samples showed, for all investigated gases, an increase of gas permeability and S values at higher temperature. Heat resistance classification among the sample as it is and stored in modified atmospheres was made. Finally all performed experiments have showed good polymer stability for the shelf-life storage potatoes under study. Study of packaging material was performed in a range of temperature, which can simulate the service condition to assess the suitability of a commercial polymer film for modified atmosphere packaging of fresh-cut potatoes minimally processed designed for catering purpose. © 2012 Institute of Food Technologists®

Single-Molecule Tracking Study of the Permeability and Transverse Width of Individual Cylindrical Microdomains in Solvent-Swollen Polystyrene-block-poly(ethylene oxide) Films.

Science.gov (United States)

Sapkota, Dol Raj; Tran-Ba, Khanh-Hoa; Elwell-Cuddy, Trevor; Higgins, Daniel A; Ito, Takashi

2016-12-01

Understanding the properties of solvent-swollen block copolymer (BCP) microdomains is important for better solvent-based control of microdomain morphology, orientation, and permeability. In this study, single-molecule tracking (SMT) was explored to assess the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene-block-poly(ethylene oxide) (PS-b-PEO) films. PS-b-PEO films comprising shear-elongated cylindrical PEO microdomains were prepared by sandwiching its benzene or tetrahydrofuran (THF) solution between two glass substrates. SMT measurements were performed at different drying times to investigate the effects of solvent evaporation on the microdomain properties. SMT data showed one-dimensional (1D) motions of single fluorescent molecules (sulforhodamine B) based on their diffusion within the cylindrical microdomains. Microdomain permeability and transverse width were assessed from the single-molecule diffusion coefficients (D SMT ) and transverse variance of the 1D trajectories (σ δ 2 ), respectively. The D SMT and σ δ 2 values from individual 1D trajectories were widely distributed with no evidence of correlation on a single molecule basis, possibly because the individual microdomains in a film were swollen to different extents. On average, microdomain permeability (D) and effective radius (r) gradually decreased within the first 3 days of drying due to solvent evaporation, and changed negligibly thereafter. PS-b-PEO films prepared from THF solutions exhibited larger changes in D and r as compared with those from benzene solutions due to the better swelling of the PEO microdomains by THF. Importantly, changes in D were more prominent than those in r, suggesting that the permeability of the PEO microdomains is very susceptible to the presence of solvent. These results reveal the unique capability of SMT to assess the properties of individual cylindrical microdomains in a solvent-swollen BCP film.

Ultra-high resistive and anisotropic CoPd-CaF2 nanogranular soft magnetic films prepared by tandem-sputtering deposition

Science.gov (United States)

Naoe, Masayuki; Kobayashi, Nobukiyo; Ohnuma, Shigehiro; Iwasa, Tadayoshi; Arai, Ken-Ichi; Masumoto, Hiroshi

2015-10-01

Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF2 matrix, and a specimen having a composition of (Co0.69Pd0.31)52-(Ca0.31F0.69)48 exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau-Lifshitz-Gilbert equation. Furthermore, it was clarified that the CaF2-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF2 matrix.

Magnetic damping phenomena in ferromagnetic thin-films and multilayers

Science.gov (United States)

Azzawi, S.; Hindmarch, A. T.; Atkinson, D.

2017-11-01

Damped ferromagnetic precession is an important mechanism underpinning the magnetisation processes in ferromagnetic materials. In thin-film ferromagnets and ferromagnetic/non-magnetic multilayers, the role of precession and damping can be critical for spintronic device functionality and as a consequence there has been significant research activity. This paper presents a review of damping in ferromagnetic thin-films and multilayers and collates the results of many experimental studies to present a coherent synthesis of the field. The terms that are used to define damping are discussed with the aim of providing consistent definitions for damping phenomena. A description of the theoretical basis of damping is presented from early developments to the latest discussions of damping in ferromagnetic thin-films and multilayers. An overview of the time and frequency domain methods used to study precessional magnetisation behaviour and damping in thin-films and multilayers is also presented. Finally, a review of the experimental observations of magnetic damping in ferromagnetic thin-films and multilayers is presented with the most recent explanations. This brings together the results from many studies and includes the effects of ferromagnetic film thickness, the effects of composition on damping in thin-film ferromagnetic alloys, the influence of non-magnetic dopants in ferromagnetic films and the effects of combining thin-film ferromagnets with various non-magnetic layers in multilayered configurations.

Magnetic volcanos in gadolinium Langmuir-Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Tishin, A.M. E-mail: amt@mailaps.org; Snigirev, O.V.; Khomutov, G.B.; Gudoshnikov, S.A.; Bohr, J

2001-09-01

Magnetic, structural and electronic properties of Langmuir-Blodgett films with incorporated Gd{sup 3+} ions has been detected using a scanning DC SQUID microscope, scanning electron microscope and X-ray diffraction. The magnetic images of 28 and 50 layer thick films at 77 K have been obtained after in-plane and out-of-plane pre-magnetization in a field of 1.4 T at 300 K. Randomly placed 'magnetic volcanos' with a remanent magnetic moment of the order of 10{sup -13} A m{sup 2} was observed. A decay of the remanent magnetization with a characteristic time of about 120 h was observed. It is suggested that the magnetic order is relatively long ranged, and that topological defects (vortices) lead to the observed out-of-plane field lines, and are responsible for the magnetic volcanos. Finally, it is hypothesized that a similar topology of field lines is responsible for superconductivity as observed in ceramic high-T{sub C} superconductors.

Calculation of the magnetic anisotropy energy and finite-temperature magnetic properties of transition-metal films

International Nuclear Information System (INIS)

Garibay-Alonso, R; Villasenor-Gonzalez, P; Dorantes-Davila, J; Pastor, G M

2004-01-01

The magnetic anisotropy energy at the interface (IMAE) of Co films deposited on the Pd(111) surface are determined in the framework of a self-consistent, real-space tight-binding method at zero temperature. Significant spin moments are induced at the Pd atoms at the interface which have an important influence on the observed reorientation transitions as a function of Co film thickness. Film-substrate hybridizations are therefore crucial for the magneto-anisotropic behaviour of thin transition-metal films deposited on metallic non-magnetic substrates. Furthermore, using a real-space recursive expansion of the local Green function and within the virtual-crystal approximation we calculate the magnetization curves and the Curie temperature T C for free-standing Fe films

Probing Active Nematic Films with Magnetically Manipulated Colloids

Science.gov (United States)

Rivas, David; Chen, Kui; Henry, Robert; Reich, Daniel; Leheny, Robert

We study microtubule-based extensile active nematic films using rod-like and disk-shaped magnetic colloids to probe the mechanical and hydrodynamic properties of this quasi-two dimensional out-of-equilibrium system. The active nematics are driven by molecular motors that hydrolyze ATP and cause sliding motion between microtubular bundles. This motion produces a dynamic nematic director field, which continuously creates pairs of +1/2 and -1/2 defects. In the absence of externally applied forces or torques, we observe that the magnetic rods in contact with the films align with the local director, indicating the existence of mechanical coupling between the film and probe. By applying known magnetic torques to the rods and observing their rotation with respect to the director, we gain insight into this coupling. We also find that by rotating magnetic microdisks using magnetic fields, hydrodynamic flows are produced that compete with the films' intrinsic flow, leading to significant effects on the director field and the defect landscape. At certain rotation rates, the disks produce a vortex-like structure in the director field and cause the creation and shedding of defects from the disk boundary.

Magnetic loss, permeability, and anisotropy compensation in CoO-doped Mn-Zn ferrites

Science.gov (United States)

Beatrice, Cinzia; Dobák, Samuel; Tsakaloudi, Vasiliki; Ragusa, Carlo; Fiorillo, Fausto; Martino, Luca; Zaspalis, Vassilis

2018-04-01

Mn-Zn ferrite samples prepared by conventional solid state reaction method and sintering at 1325 °C were Co-enriched by addition of CoO up to 6000 ppm and characterized versus frequency (DC - 1GHz), peak polarization (2 mT - 200 mT), and temperature (23 °C - 120 °C). The magnetic losses at room temperature are observed to pass through a deep minimum value around 4000 ppm CoO at all polarizations values. This trend is smoothed out either by approaching the MHz range or by increasing the temperature. Conversely, the initial permeability attains its maximum value around the same CoO content, while showing moderate monotonical decrease with increasing CoO at the typical working temperatures of 80 - 100 °C. The energy losses, measured by a combination of fluxmetric and transmission line methods, are affected by the eddy currents, on the conventional 5 mm thick ring samples, only beyond a few MHz. Their assessment relies on the separation of rotational and domain wall processes, which can be done by analysis of the complex permeability and its frequency behavior. This permits one, in particular, to calculate the magnetic anisotropy and its dependence on CoO content and temperature and bring to light its decomposition into the host lattice and Co2+ temperature dependent contributions. The temperature and doping dependence of initial permeability and magnetic losses can in this way be qualitatively justified, without invoking the passage through zero value of the effective anisotropy constant upon doping.

Electrodeposited Ni-W magnetic thin films with columnar nanocrystallites

International Nuclear Information System (INIS)

Sulitanu, N.; Brinza, F.

2002-01-01

Nanocrystalline Ni-W thin films (140 nm) containing from zero to 18 wt % W were electrolytically prepared and structural and magnetic characterized. XRD, SEM and TEM investigations have revealed that all segregated Ni columns are fcc-type whose [111] axis is oriented perpendicular to the film plane and have 140 nm in height and 6-27 nm in diameter. Depending on film composition, two types of nanostructures were observed: (a) single-phase nanostructure ( i nterphases , namely W enriched particles boundaries, and (b) two-phase nanostructure (7-18 wt %) in which a second Ni-W amorphous phase or even amorphous-disordered mixture separates the magnetic columnar Ni nanocrystallites (d = 6-14 nm). The columnar crystallites have an easy magnetization direction along their long axis mainly due to the in-plane internal biaxial stresses. Magnetic characteristics of prepared thin films are presented. (Authors)

Magnetic hysteresis measurements of thin films under isotropic stress.

Science.gov (United States)

Holland, Patrick; Dubey, Archana; Geerts, Wilhelmus

2000-10-01

Nowadays, ferromagnetic thin films are widely applied in devices for information technology (credit cards, video recorder tapes, floppies, hard disks) and sensors (air bags, anti-breaking systems, navigation systems). Thus, with the increase in the use of magnetic media continued investigation of magnetic properties of materials is necessary to help in determining the useful properties of materials for new or improved applications. We are currently interested in studying the effect of applied external stress on Kerr hysteresis curves of thin magnetic films. The Ni and NiFe films were grown using DC magnetron sputtering with Ar as the sputter gas (pAr=4 mTorr; Tsub=55-190 C). Seed and cap layers of Ti were used on all films for adhesion and oxidation protection, respectively. A brass membrane pressure cell was designed to apply in-plane isotropic stress to thin films. In this pressure cell, gas pressure is used to deform a flexible substrate onto which a thin magnetic film has been sputtered. The curvature of the samples could be controlled by changing the gas pressure to the cell. Magneto-Optical in-plane hysteresis curves at different values of strain were measured. The results obtained show that the stress sensitivity is dependent on the film thickness. For the 500nm NiFe films, the coercivity strongly decreased as a function of the applied stress.

Magnetization pinning in conducting films demonstrated using broadband ferromagnetic resonance

Science.gov (United States)

Kostylev, M.; Stashkevich, A. A.; Adeyeye, A. O.; Shakespeare, C.; Kostylev, N.; Ross, N.; Kennewell, K.; Magaraggia, R.; Roussigné, Y.; Stamps, R. L.

2010-11-01

The broadband microstrip ferromagnetic resonance (FMR), cavity FMR, and Brillouin light scattering spectroscopy techniques have been applied for detection and characterization of a magnetic inhomogeneity in a film sample. In the case of a 100 nm thick permalloy film, an additional magnetically depleted top sublayer has been detected due to pinning effect it produces on the magnetization in the bulk of the film. The pinning results in appearance of an exchange standing spin wave mode in the broadband FMR absorption spectrum, whose amplitudes are different depending on whether the film or the film substrate faces the microstrip transducer. Comparison of the experimental amplitudes for this mode with results of our theory for both film placements revealed that the depleted layer is located at the film surface facing away from the film substrate. Subsequent broadband FMR characterization of a large number of other presumably single-layer films with thicknesses in the range 30-100 nm showed the same result.

Surface and magnetic characteristics of Ni-Mn-Ga/Si (100) thin film

Energy Technology Data Exchange (ETDEWEB)

Kumar, S. Vinodh; Pandyan, R. Kodi; Mahendran, M., E-mail: manickam-mahendran@tce.edu, E-mail: perialangulam@gmail.com [Smart Materials Lab, Department of Physics, Thiagarajar College of Engineering, Madurai – 625 015 (India); Raja, M. Manivel [Defence Metallurgical Research Laboratory, Hyderabad – 500 058 (India); Pandi, R. Senthur [School of Advanced Sciences, VIT University, Vellore – 632 014 (India)

2016-05-23

Polycrystalline Ni-Mn-Ga thin films have been deposited on Si (100) substrate with different film thickness. The influence of film thickness on the phase structure and magnetic domain of the films has been examined by scanning electron microscope, atomic force microscopy and magnetic force microscopy. Analysis of structural parameters indicates that the film at lower thickness exhibits the coexistence of both austenite and martensite phase, whereas at higher thickness L1{sub 2} cubic non magnetic phase is noticed. The grains size and the surface roughness increase along with the film thickness and attain the maximum of 45 nm and 34.96 nm, respectively. At lower film thickness, the magnetic stripe domain is found like maze pattern with dark and bright images, while at higher thickness the absence of stripe domains is observed. The magnetic results reveal that the films strongly depend on their phase structure and microstructure which influence by the film thickness.

Applied magnetic field angle dependence of the static and dynamic magnetic properties in FeCo films during the deposition

Energy Technology Data Exchange (ETDEWEB)

Cao, Derang; Zhu, Zengtai; Feng, Hongmei; Pan, Lining; Cheng, Xiaohong; Wang, Zhenkun [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Qingfang, E-mail: liuqf@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2016-10-15

FeCo films were prepared by a simple and convenient electrodeposition method. An external magnetic field was applied to the film to induce magnetic anisotropy during deposition. Comparing with the previous work, the angle between the direction of applied magnetic field and film plane is changed from in-plane to out-plane. The influence of the applied magnetic field on magnetic properties was investigated. As a result, it can be found that the in-plane anisotropy is driven by the in-plane component of the magnetic field applied during growth. In addition, the result can also be confirmed by the dynamic magnetic anisotropy of the film obtained by vector network analyzer ferromagnetic resonance technique. - Highlights: • FeCo films were prepared by electrodeposition method. • An external magnetic field was applied to induce anisotropy during deposition. • The direction of applied magnetic field is changed from in-plane to out-plane. • The magnetic properties of films were investigated by vector network analyzer. • The in-plane anisotropy is driven by the in-plane component of the field.

Negative permeability from random particle composites

Energy Technology Data Exchange (ETDEWEB)

Hussain, Shahid, E-mail: shussain2@qinetiq.com

2017-04-15

Artificial media, such as those composed of periodically-spaced wires for negative permittivity and split ring resonators for negative permeability have been extensively investigated for negative refractive index (NRI) applications (Smith et al., 2004; Pendry et al., 1999) [1,2]. This paper presents an alternative method for producing negative permeability: granular (or particulate) composites incorporating magnetic fillers. Artificial media, such as split-ring resonators, are designed to produce a magnetic resonance feature, which results in negative permeability over a narrow frequency range about the resonance frequency. The position of the feature is dependent upon the size of the inclusion. The material in this case is anisotropic, such that the feature is only observable when the materials are orientated in a specific direction relative to the applied field. A similar resonance can be generated in magnetic granular (particulate) materials: ferromagnetic resonance from the natural spin resonance of particles. Although the theoretical resonance profiles in granular composites shows the permeability dipping to negative values, this is rarely observed experimentally due to resonance damping effects. Results are presented for iron in spherical form and in flake form, dispersed in insulating host matrices. The two particle shapes show different permeability performance, with the magnetic flakes producing a negative contribution. This is attributed to the stronger coupling with the magnetic field resulting from the high aspect ratio of the flakes. The accompanying ferromagnetic resonance is strong enough to overcome the effects of damping and produce negative permeability. The size of random particle composites is not dictated by the wavelength of the applied field, so the materials are potentially much thinner than other, more traditional artificial composites at microwave frequencies. - Highlights: • Negative permeability from random particle composites is

Metal Amorphous Nanocomposite (MANC) Alloy Cores with Spatially Tuned Permeability for Advanced Power Magnetics Applications

Science.gov (United States)

Byerly, K.; Ohodnicki, P. R.; Moon, S. R.; Leary, A. M.; Keylin, V.; McHenry, M. E.; Simizu, S.; Beddingfield, R.; Yu, Y.; Feichter, G.; Noebe, R.; Bowman, R.; Bhattacharya, S.

2018-06-01

Metal amorphous nanocomposite (MANC) alloys are an emerging class of soft magnetic materials showing promise for a range of inductive components targeted for higher power density and higher efficiency power conversion applications including inductors, transformers, and rotating electrical machinery. Magnetization reversal mechanisms within these alloys are typically determined by composition optimization as well as controlled annealing treatments to generate a nanocomposite structure composed of nanocrystals embedded in an amorphous precursor. Here we demonstrate the concept of spatially varying the permeability within a given component for optimization of performance by using the strain annealing process. The concept is realized experimentally through the smoothing of the flux profile from the inner to outer core radius achieved by a monotonic variation in tension during the strain annealing process. Great potential exists for an extension of this concept to a wide range of other power magnetic components and more complex spatially varying permeability profiles through advances in strain annealing techniques and controls.

High-frequency domain wall excitations in magnetic garnet films with in-plane magnetization

International Nuclear Information System (INIS)

Synogach, V.T.; Doetsch, H.

1996-01-01

Magnetic garnet films of compositions (YBi) 3 Fe 5 O 12 and (LuBi) 3 Fe 5 O 12 are grown by liquid-phase epitaxy on [110]- and [100]-oriented substrates of gadolinium gallium garnet, respectively. All films have in-plane magnetization. 180 degree and 90 degree domain walls in these films are studied by microwave technique. In addition to the known low-frequency mode of wall translation new multiple resonant modes of both 90 degree and 180 degree domain walls with very small linewidth (4.2 MHz) are observed at frequencies near 1 GHz. Resonances are effectively excited by an rf magnetic field which is parallel or perpendicular to the wall plane. Resonance frequencies are shown to have nonlinear dispersion dependence on the mode number: they decrease with increasing in-plane magnetic field normal to the wall plane. copyright 1996 The American Physical Society

Effect of argon ion etching on the magnetic properties of FeCoB films

Energy Technology Data Exchange (ETDEWEB)

Zhu, Junwei; Zhou, Kan; Yang, Yi; Tang, Dongming; Zhang, Baoshan, E-mail: malab@nju.edu.cn; Lu, Mu; Lu, Huaixian

2015-01-15

In this paper, a new method to modify Ta underlayers by an argon ion etching technology is introduced. Surface roughness of Ta underlayers, as well as soft magnetic properties of post-deposited FeCoB films can be improved by applying a proper ion etching process. The reduction of magnetic coercivity of FeCoB films deposited on the modified Ta underlayers is attributed to the improvement of interfacial roughness, which can reduce magnetic ripples in magnetic films. The microwave damping linewidth of magnetic films is also found to be related to the interfacial roughness. Ta underlayers modified by the ion etching can reduce the influence of two-magnon scattering effect, and thus tune microwave properties of magnetic films. All the results prove that argon ion etching is an effective way to tailor magnetic properties of magnetic films. - Highlights: • We believe that our method to tune the magnetic film properties will be interesting for general readers of Journal of Magnetism and Magnetic Materials. • In the paper, argon ion etching is applied to the Ta underlayer before the FeCoB film is deposited on it. • The modified interface roughness has effectively improved the magnetic properties, including the static magnetic and microwave performance. • The method is valuable for other underlayer/magnetic film systems.

Microstructural and magnetic properties of thin obliquely deposited films: A simulation approach

Energy Technology Data Exchange (ETDEWEB)

Solovev, P.N., E-mail: platon.solovev@gmail.com [Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Izotov, A.V. [Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Belyaev, B.A. [Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, 50/38, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Siberian Federal University, 79, pr. Svobodnyi, Krasnoyarsk 660041 (Russian Federation); Reshetnev Siberian State Aerospace University, 31, pr. Imeni Gazety “Krasnoyarskii Rabochii”, Krasnoyarsk 660014 (Russian Federation)

2017-05-01

The relation between microstructural and magnetic properties of thin obliquely deposited films has been studied by means of numerical techniques. Using our developed simulation code based on ballistic deposition model and Fourier space approach, we have investigated dependences of magnetometric tensor components and magnetic anisotropy parameters on the deposition angle of the films. A modified Netzelmann approach has been employed to study structural and magnetic parameters of an isolated column in the samples with tilted columnar microstructure. Reliability and validity of used numerical methods is confirmed by a good agreement of the calculation results with each other, as well as with our experimental data obtained by the ferromagnetic resonance measurements of obliquely deposited thin Ni{sub 80}Fe{sub 20} films. The combination of these numerical methods can be used to design a magnetic film with a desirable value of uniaxial magnetic anisotropy and to extract the obliquely deposited film structure from only magnetic measurements. - Highlights: • We present a simulation approach to study a relation between structural and magnetic properties of oblique films. • The calculated dependence of magnetic anisotropy on a deposition angle accords well with the experiment. • A modified Netzelmann approach is proposed. • It allows for the computation of magnetic and structural parameters of an isolated column. • Proposed approach can be used for theoretical studies and for characterization of oblique films.

Magnetic properties of sputtered Permalloy/molybdenum multilayers

International Nuclear Information System (INIS)

Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C.; Ranchal, R.

2011-01-01

In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni 80 Fe 20 )/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

Thin films on the basis of magnetic nanoparticles

Directory of Open Access Journals (Sweden)

G. Alimbekova

2012-09-01

Full Text Available The present work is to study the adsorption of magnetic nanoparticles in the structure of nanohybrid films by layer-by-layer (LbL method. Obtained by UV-VIS absorption spectra of 5% magnetic nanoparticles and the aqueous solution polyvinyl alcohol consisting of 5 and 10 nanohybrid layers. Analysis of the optical absorption spectra shows the homogeneity and mechanical stability of the nanohybrid films.

Fabrication and Magnetic Properties of Fe65Co35–ZnO Nano-Granular Films

Directory of Open Access Journals (Sweden)

Wang Guowei

2010-01-01

Full Text Available Abstract A series of nano-granular films composed of magnetic metal (Fe65Co35 granules with a few nanometers in size and semiconductor oxide (ZnO have been fabricated by a magnetron sputtering method, and excellent soft magnetic properties have been achieved in a wide metal volume fraction (x range for as-deposited samples due to the exchange coupling between FeCo granules (a ferromagnetic interaction in nano-scale. In a wide range (0.53 < x < 0.71, the films exhibit coercivity H C not exceeding 15 Oe, along with high resistivity. Especially for the sample with x = 0.67, coercivities in hard and easy axes are 1.43 and 7.08 Oe, respectively, 4πM S = 9.85 kg, and ρ reaches 2.06 × 103 μΩ cm. The dependence of complex permeability μ = μ′ − jμ″ on frequency shows that the real part μ′ is more than 100 below 1.83 GHz and that the ferromagnetic resonance frequency reaches 2.31 GHz, implying the promising for high frequency application. The measured negative temperature coefficient of resistivity reveals that may be the weak localized electrons existing in samples mediate the exchange coupling.

Finite element method calculations of GMI in thin films and sandwiched structures: Size and edge effects

International Nuclear Information System (INIS)

Garcia-Arribas, A.; Barandiaran, J.M.; Cos, D. de

2008-01-01

The impedance values of magnetic thin films and magnetic/conductor/magnetic sandwiched structures with different widths are computed using the finite element method (FEM). The giant magneto-impedance (GMI) is calculated from the difference of the impedance values obtained with high and low permeability of the magnetic material. The results depend considerably on the width of the sample, demonstrating that edge effects are decisive for the GMI performance. It is shown that, besides the usual skin effect that is responsible for GMI, an 'unexpected' increase of the current density takes place at the lateral edge of the sample. In magnetic thin films this effect is dominant when the permeability is low. In the trilayers, it is combined with the lack of shielding of the central conductor at the edge. The resulting effects on GMI are shown to be large for both kinds of samples. The conclusions of this study are of great importance for the successful design of miniaturized GMI devices

Magnetic properties of novel epitaxial films

International Nuclear Information System (INIS)

Bader, S.D.; Moog, E.R.

1986-09-01

The surface magneto-optic Kerr effect (SMOKE) is used to explore the magnetism of ultra-thin Fe Films extending into the monolayer regime. Both bcc α-Fe and fcc γ-Fe single-crystalline, multilayer films are prepared on the bulk-terminated (1 x 1) structures of Au(100) and Cu(100), respectively. The characterizations of epitaxy and growth mode are performed using low energy electron diffraction and Auger electron spectroscopy. Monolayer-range Fe/Au(100) is ferromagnetic with a lower Curie temperature than bulk α-Fe. The controversial γ-Fe/Cu(100) system exhibits a striking, metastable, surface magnetic phase at temperatures above room temperature, but does not exhibit bulk ferromagnetism

Influence of magnetic disorders on quantum anomalous Hall effect in magnetic topological insulator films beyond the two-dimensional limit

Science.gov (United States)

Xing, Yanxia; Xu, Fuming; Cheung, King Tai; Sun, Qing-feng; Wang, Jian; Yao, Yugui

2018-04-01

Quantum anomalous Hall effect (QAHE) has been experimentally realized in magnetic topological insulator (MTI) thin films fabricated on magnetically doped {({{Bi}},{{Sb}})}2{{{Te}}}3. In an MTI thin film with the magnetic easy axis along the normal direction (z-direction), orientations of magnetic dopants are randomly distributed around the magnetic easy axis, acting as magnetic disorders. With the aid of the non-equilibrium Green's function and Landauer–Büttiker formalism, we numerically study the influence of magnetic disorders on QAHE in an MTI thin film modeled by a three-dimensional tight-binding Hamiltonian. It is found that, due to the existence of gapless side surface states, QAHE is protected even in the presence of magnetic disorders as long as the z-component of magnetic moment of all magnetic dopants are positive. More importantly, such magnetic disorders also suppress the dissipation of the chiral edge states and enhance the quality of QAHE in MTI films. In addition, the effect of magnetic disorders depends very much on the film thickness, and the optimal influence is achieved at certain thickness. These findings are new features for QAHE in three-dimensional systems, not present in two-dimensional systems.

Angular tuning of the magnetic birefringence in rippled cobalt films

Energy Technology Data Exchange (ETDEWEB)

Arranz, Miguel A., E-mail: MiguelAngel.Arranz@uclm.es [Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, José M. [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain)

2015-06-22

We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

Angular tuning of the magnetic birefringence in rippled cobalt films

International Nuclear Information System (INIS)

Arranz, Miguel A.; Colino, José M.

2015-01-01

We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes

Studying behavior of multilayer materials: A 1-D model correlated to magnetic domain walls through complex permeability

International Nuclear Information System (INIS)

Ahmadi, B.; Chazal, H.; Waeckerle, T.; Roudet, J.

2008-01-01

Multilayer cores are suitable for integrated planar magnetic components. We proposed here to investigate the frequency behavior of multilayer nanocrystalline cores in the frame of a one-dimensional (1-D) electromagnetic propagation model. Electromagnetic wave equations are considered to explain the phenomena from the macroscopic point of view. A domain wall description is considered to take into account non-homogeneity of magnetic media. This mesoscopic model is correlated to macroscopic model through complex permeability. The scope of validity of the model is determined by means of indirect permeability measurement. Finally, the behavior of the multilayer core is predicted by using an equivalent electrical circuit and will interest component designers

Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

Science.gov (United States)

Payne, Allison H; Hawryluk, Gregory W; Anzai, Yoshimi; Odéen, Henrik; Ostlie, Megan A; Reichert, Ethan C; Stump, Amanda J; Minoshima, Satoshi; Cross, Donna J

2017-12-01

Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.

Neutron reflectivity of electrodeposited thin magnetic films

International Nuclear Information System (INIS)

Cooper, Joshaniel F.K.; Vyas, Kunal N.; Steinke, Nina-J.; Love, David M.; Kinane, Christian J.; Barnes, Crispin H.W.

2014-01-01

Highlights: • Electrodeposited magnetic bi-layers were measured by polarised neutron reflectivity. • When growing a CoNiCu alloy from a single bath a Cu rich region is initially formed. • This Cu rich region is formed in the first layer but not subsequent ones. • Ni deposition is inhibited in thin film growth and Co deposits anomalously. • Alloy magnetism and neutron scattering length give a self-consistent model. - Abstract: We present a polarised neutron reflectivity (PNR) study of magnetic/non-magnetic (CoNiCu/Cu) thin films grown by single bath electrodeposition. We find that the composition is neither homogeneous with time, nor consistent with bulk values. Instead an initial, non-magnetic copper rich layer is formed, around 2 nm thick. This layer is formed by the deposition of the dilute, but rapidly diffusing, Cu 2+ ions near the electrode surface at the start of growth, before the region is depleted and the deposition becomes mass transport limited. After the region has been depleted, by growth etc., this layer does not form and thus may be prevented by growing a copper buffer layer immediately preceding the magnetic layer growth. As has been previously found, cobalt deposits anomalously compared to nickel, and even inhibits Ni deposition in thin films. The layer magnetisation and average neutron scattering length are fitted independently but both depend upon the alloy composition. Thus these parameters can be used to check for model self-consistency, increasing confidence in the derived composition

Magnetic and electromagnetic properties of Pr doped strontium ferrite/polyaniline composite film

Energy Technology Data Exchange (ETDEWEB)

Huang, Ying; Li, Yuqing; Wang, Yan, E-mail: wangyan287580632@126.com

2014-11-15

This paper reported three acid (including hydrochloric acid HCl, p-toluenesulfonic acid PTS and D-camphor-10-acid CSA) doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite film and the HCl–PANI film prepared by a sol–gel method and in-situ oxidative polymerization. The characteristics of the film phase structure, surface morphology, conductivity and magnetic and electromagnetic properties were studied by using XRD, XPS, FESEM, four-probe tester, VSM and Vector Network Analyzer. The resistivity of organic acid doped composite films is higher than that of the HCl doped one. The saturation and remanent magnetization of PTS and HCl doped composite films are greater than the CSA-doped one; however, the coercivity of the three acid doped composite films is basically 5546 Oe. The saturation magnetization, remanent magnetization and coercivity of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film are greater than those of the SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}–PANI composite film. In the frequency range of 8–12 GHz, the dielectric loss of HCl–PANI film is the maximum, and the dielectric loss of SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film is the minimum; the magnetic loss of the four films is in descending order as SrPr{sub 0.2}Fe{sub 11.8}O{sub 19} film, PrSrM/(HCl–PANI) composite film, PrSrM/(CSA–PANI) and HCl–PANI film. - Highlights: • Synthesizing three acid doped SrPr{sub 0.2}Fe{sub 11.8}O{sub 19}/PANI composite films. • By sol–gel method and in-situ oxidative polymerization. • With excellent magnetic and electromagnetic properties. • The particular coating structure of PANI and Sr-ferrite. • Great interest for magnetic material and microwave absorbers.

Invariance of the magnetic behavior and AMI in ferromagnetic biphase films with distinct non-magnetic metallic spacers

Energy Technology Data Exchange (ETDEWEB)

Silva, E.F. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil); Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Gamino, M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Instituto de Física, Universidade Federal do Rio Grande de Sul, 91501-970 Porto Alegre, RS (Brazil); Andrade, A.M.H. de [Instituto de Física, Universidade Federal do Rio Grande de Sul, 91501-970 Porto Alegre, RS (Brazil); Vázquez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid (Spain); Correa, M.A. [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil); Bohn, F., E-mail: felipebohn@fisica.ufrn.br [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil)

2017-02-01

We investigate the quasi-static magnetic, magnetotransport, and dynamic magnetic properties in ferromagnetic biphase films with distinct non-magnetic metallic spacer layers. We observe that the nature of the non-magnetic metallic spacer material does not have significant influence on the overall biphase magnetic behavior, and, consequently, on the magnetotransport and dynamic magnetic responses. We focus on the magnetoimpedance effect and verify that the films present asymmetric magnetoimpedance effect. Moreover, we explore the possibility of tuning the linear region of the magnetoimpedance curves around zero magnetic field by varying the probe current frequency in order to achieve higher sensitivity values. The invariance of the magnetic behavior and the asymmetric magnetoimpedance effect in ferromagnetic biphase films with distinct non-magnetic metallic spacers place them as promising candidates for probe element and open possibilities to the development of lower-cost high sensitivity linear magnetic field sensor devices.

Characterization of magnetization processes in nanostructured rare earth-transition metal films

International Nuclear Information System (INIS)

Zheng Guangping; Zhan Yangwen; Liu Peng; Li Mo

2003-01-01

We synthesize rare earth-transition metal (RE-TM) amorphous films using the electrodeposition method (RE=Nd, Gd and TM=Co). Nanocrystructured RE-TM films are prepared by thermal treatment of as-synthesized films below the glass-crystal transition temperature. Based on the magnetoelastic effect, the magnetization processes in nanostructured samples are characterized by acoustic internal friction measurements using the vibrating-reed technique. Since internal friction and the Young's modulus are sensitive to grain boundary and magnetic domains movement, this technique seems to characterize the effects of nanostructures on the magnetization processes in RE-TM films well. We find that the magnetoelastic effect in nanostructured RE-TM film increases with an increase in grain size

Temperature dependence of magnetically dead layers in ferromagnetic thin-films

Directory of Open Access Journals (Sweden)

M. Tokaç

2017-11-01

Full Text Available Polarized neutron reflectometry has been used to study interface magnetism and magnetic dead layers in model amorphous CoFeB:Ta alloy thin-film multilayers with Curie temperatures tuned to be below room-temperature. This allows temperature dependent variations in the effective magnetic thickness of the film to be determined at temperatures that are a significant fraction of the Curie temperature, which cannot be achieved in the material systems used for spintronic devices. In addition to variation in the effective magnetic thickness due to compositional grading at the interface with the tantalum capping layer, the key finding is that at the interface between ferromagnetic film and GaAs(001 substrate local interfacial alloying creates an additional magnetic dead-layer. The thickness of this magnetic dead-layer is temperature dependent, which may have significant implications for elevated-temperature operation of hybrid ferromagnetic metal-semiconductor spintronic devices.

Magnetic property effect on transport processes in resistance spot welding

Energy Technology Data Exchange (ETDEWEB)

Wei, P S [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan 80424 (China); Wu, T H, E-mail: pswei@mail.nsysu.edu.tw, E-mail: wux0064@gmail.com [Department of Mechanical Engineering, Yung Ta Institute of Technology and Commerce, Pintong, Taiwan 909 (China)

2011-08-17

This study investigates the effects of the Curie temperature and magnetic permeability on transport variables, solute distribution and nugget shapes during resistance spot welding. The Curie temperature is the temperature below which a metal or alloy is ferromagnetic with a high magnetic permeability, and above which it is paramagnetic with a small magnetic permeability. The model proposed here accounts for electromagnetic force, heat generation and contact resistance at the faying surface and electrode-workpiece interfaces and bulk resistance in workpieces. Contact resistance includes constriction and film resistances, which are functions of hardness, temperature, electrode force and surface condition. The computed results show that transport variables and nugget shapes can be consistently interpreted from the delay of response time and jump of electric current density as a result of finite magnetic diffusion, rather than through the examination of the variations of dynamic electrical resistance with time. The molten nugget on the faying surface is initiated earlier with increasing magnetic permeability and Curie temperature. A high Curie temperature enhances convection and solute mixing, and readily melts through the workpiece surface near the electrode edge. Any means to reduce the Curie temperature or magnetic permeability, such as adjusting the solute content, can be a good way to control weld quality. This study can also be applied to interpret the contact problems encountered in various electronics and packaging technologies, and so on.

Structure and magnetization of Co4N thin film

Science.gov (United States)

Pandey, Nidhi; Gupta, Mukul; Gupta, Rachana; Rajput, Parasmani; Stahn, Jochen

2018-02-01

In this work, we studied the local structure and the magnetization of Co4N thin films deposited by a reactive dc magnetron sputtering process. The interstitial incorporation of N atoms in a fcc Co lattice is expected to expand the structure. This expansion yields interesting magnetic properties e.g. a larger magnetic moment (than Co) and a very high value of spin polarization ratio in Co4N . By optimizing the growth conditions, we prepared Co4N film having lattice parameter close to its theoretically predicted value. The N concentration was measured using secondary ion mass spectroscopy. Detailed magnetization measurements using bulk magnetization method and polarized neutron reflectivity confirm that the magnetic moment of Co in Co4N is higher than that of Co.

Effect of magnetic field on the growth of Be films prepared by thermal evaporation

International Nuclear Information System (INIS)

Li, Kai; Luo, Bing-chi; Tan, Xiu-lan; Zhang, Ji-qiang; Wu, Wei-dong; Liu, Ying

2014-01-01

Highlights: • The Be films were prepared on Si (1 0 0) substrates with and without a magnetic field by thermal evaporation, respectively. • The grain diameter in the Be film transited from 300 nm to 18 nm by application of the magnetic field. • The surface roughness of the Be film decreased from 61 nm to 3 nm by application of the magnetic field. • The Be film grown with the magnetic field was easily oxidized due to its refined grains and the oxidation was gradually decreased with increasing the etching depth in the film. - Abstract: Grain refinement of beryllium deposits is studied as a significant subject for beryllium capsule in the Inertial Confinement Fusion project. The Be films were prepared on the Si (1 0 0) substrates by thermal evaporation with and without a magnetic field, respectively. The two separate groups of prepared Be films were characterized. The results showed the grain diameter in the Be film transited from 300 nm to 18 nm and the surface roughness of the Be film decreased from 61 nm to 3 nm by application of the magnetic field during the deposition process of Be coating. However, the Be film grown with the magnetic field was easily oxidized in comparison with that grown without magnetic field due to the refined grains, and the oxidation was gradually decreased with the increase of etching depth in the Be film. The reason for grain refinement of Be film was also qualitatively described

Magnetic x-ray dichroism in ultrathin epitaxial films

Energy Technology Data Exchange (ETDEWEB)

Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Cummins, T.R. [Univ. of Missouri, Rolla, MO (United States)] [and others

1997-04-01

The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.

Magnetic x-ray dichroism in ultrathin epitaxial films

International Nuclear Information System (INIS)

Tobin, J.G.; Goodman, K.W.; Cummins, T.R.

1997-01-01

The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction

Numerical study and design optimization of electromagnetic energy harvesters integrated with flexible magnetic materials

Energy Technology Data Exchange (ETDEWEB)

Yoon, Sang Won [Hanyang University, Seoul (Korea, Republic of)

2017-05-15

This study presents a new design of an electromagnetic energy harvester integrated with a soft magnetic material. The harvester design optimizes the magnetic material characteristics and the size of a rectangular permanent magnet. The design employs a complete magnetic circuit made of (1) a thin-film soft magnetic material that facilitates a flexible but highly (magnetically) permeable beam and (2) an optimally-sized magnet that maximizes the harvester performance. The design is demonstrated to reduce magnetic flux leakage, and thus considerably enhances both magnetic flux density (B) and its change by time (dB/dt), which both influence harvester performance. The improvement in harvester performances strongly depends on critical design parameters, especially, the magnet size and characteristics of magnetic materials, including permeability, stiffness, and thickness. The analyses conclude that recently-introduced nanomaterials (having ultrahigh magnetic permeability) can potentially innovate harvester performances. However, the performance may be degraded without design optimization. Once optimized, the integrated nanomaterials facilitate a significant improvement compared with a conventional design without integrated magnetic materials.

Numerical study and design optimization of electromagnetic energy harvesters integrated with flexible magnetic materials

International Nuclear Information System (INIS)

Yoon, Sang Won

2017-01-01

This study presents a new design of an electromagnetic energy harvester integrated with a soft magnetic material. The harvester design optimizes the magnetic material characteristics and the size of a rectangular permanent magnet. The design employs a complete magnetic circuit made of (1) a thin-film soft magnetic material that facilitates a flexible but highly (magnetically) permeable beam and (2) an optimally-sized magnet that maximizes the harvester performance. The design is demonstrated to reduce magnetic flux leakage, and thus considerably enhances both magnetic flux density (B) and its change by time (dB/dt), which both influence harvester performance. The improvement in harvester performances strongly depends on critical design parameters, especially, the magnet size and characteristics of magnetic materials, including permeability, stiffness, and thickness. The analyses conclude that recently-introduced nanomaterials (having ultrahigh magnetic permeability) can potentially innovate harvester performances. However, the performance may be degraded without design optimization. Once optimized, the integrated nanomaterials facilitate a significant improvement compared with a conventional design without integrated magnetic materials.

Effects of topography on the local variation in the magnetization of ultrasoft magnetic films : a Lorentz microscopy study

NARCIS (Netherlands)

Chechenin, N.G.; de Hosson, J.T.M.; Boerma, D.O

2003-01-01

This paper concentrates on a detailed analysis of Lorentz transmission electron microscopy (LTEM) observations in the study of the magnetic properties of soft magnetic films. Besides ripple fringes in the LTEM image that are commonly observed in nanocrystalline soft magnetic films, there also

Investigation of the magnetic properties of electrodeposited NiFe thin films

International Nuclear Information System (INIS)

Bakkaloglu, O. F.; Bedir, M.; Oeztas, M.; Karahan, I. H.

2002-01-01

Most magnetic devices used today are based on the magnetic thin film. Rapid and extensive developments in magnetic sensor / actuator and magnetic recording technology place a growing demand on the use of different thin film fabrication techniques for magnetic materials. The electroplating technique is especially interesting due to its low cost, high throughput and high quality of the deposits which are extensively used in the magnetic recording industry to deposit relatively thick permalloy layers. Much recent attention has focused on the electrodeposited NiFe thin films, which exhibit giant magneto resistive behaviour as well as anisotropic magnetoresistance properties. n this study, NiFe thin films were developed by using electrodeposition technique and their crystallinity structures were investigated by using x-ray diffractometer measurements. The magneto resistive properties of the samples were investigated by Wan der Pauw method with a home made electromagnet under the different magnetic fields. The magnetoresistance measurements of the samples were carried out in two configurations; current parallel ( longitudinal ) and perpendicular ( transverse ) to the magnetic field. In the longitudinal configuration giant magnetoresistance was observed while anisotropic magnetoresistance was detected in the other configuration

Effect of the number of iron oxide nanoparticle layers on the magnetic properties of nanocomposite LbL assemblies

International Nuclear Information System (INIS)

Dincer, Ilker; Tozkoparan, Onur; German, Sergey V.; Markin, Alexey V.; Yildirim, Oguz; Khomutov, Gennady B.; Gorin, Dmitry A.; Venig, Sergey B.; Elerman, Yalcin

2012-01-01

Aqueous colloidal suspension of iron oxide nanoparticles has been synthesized. Z-potential of iron oxide nanoparticles stabilized by citric acid was −35±3 mV. Iron oxide nanoparticles have been characterized by the light scattering method and transmission electron microscopy. The polyelectrolyte/iron oxide nanoparticle thin films with different numbers of iron oxide nanoparticle layers have been prepared on the surface of silicon substrates via the layer-by-layer assembly technique. The physical properties and chemical composition of nanocomposite thin films have been studied by atomic force microscopy, magnetic force microscopy, magnetization measurements, Raman spectroscopy. Using the analysis of experimental data it was established, that the magnetic properties of nanocomposite films depended on the number of iron oxide nanoparticle layers, the size of iron oxide nanoparticle aggregates, the distance between aggregates, and the chemical composition of iron oxide nanoparticles embedded into the nanocomposite films. The magnetic permeability of nanocomposite coatings has been calculated. The magnetic permeability values depend on the number of iron oxide nanoparticle layers in nanocomposite film. - Highlights: ► The magnetic properties of nanocomposite films depended on the number of iron oxide nanoparticle layers. ► The iron oxide nanoparticle phase in nanocomposite coatings is a mixture of magnetite and maghemite phases. ► The magnetite and maghemite phases depend on a number of iron oxide nanoparticle layers because the iron oxide nanoparticles are oxidized from magnetite to maghemite.

Ammonia gas permeability of meat packaging materials.

Science.gov (United States)

Karim, Faris; Hijaz, Faraj; Kastner, Curtis L; Smith, J Scott

2011-03-01

Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.

Spin-Orbit Torque-Assisted Switching in Magnetic Insulator Thin Films with Perpendicular Magnetic Anisotropy

Science.gov (United States)

Wu, Mingzhong

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque that can induce magnetization switching in a neighboring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. This presentation reports the SOT-assisted switching in heavy metal/magnetic insulator systems.1 The experiments made use of Pt/BaFe12O19 bi-layered structures. Thanks to its strong spin-orbit coupling, Pt has been widely used to produce pure spin currents in previous studies. BaFe12O19 is an M-type barium hexagonal ferrite and is often referred as BaM. It is one of the few magnetic insulators with strong magneto-crystalline anisotropy and shows an effective uniaxial anisotropy field of about 17 kOe. It's found that the switching response in the BaM film strongly depends on the charge current applied to the Pt film. When a constant magnetic field is applied in the film plane, the charge current in the Pt film can switch the normal component of the magnetization (M⊥) in the BaM film between the up and down states. The current also dictates the up and down states of the remnant magnetization when the in-plane field is reduced to zero. When M⊥ is measured by sweeping an in-plane field, the response manifests itself as a hysteresis loop, which evolves in a completely opposite manner if the sign of the charge current is flipped. When the coercivity is measured by sweeping an out-of-plane field, its value can be reduced or increased by as much as about 500 Oe if an appropriate charge current is applied. 1. P. Li, T. Liu, H. Chang, A. Kalitsov, W. Zhang, G. Csaba, W. Li, D. Richardson, A. Demann, G. Rimal, H. Dey, J. S. Jiang, W. Porod, S. Field, J. Tang, M. C. Marconi, A. Hoffmann, O. Mryasov, and M. Wu, Nature Commun. 7:12688 doi: 10.1038/ncomms12688 (2016).

Magnetism in spin-coated pristine TiO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Hassini, Awatef [IUT de Blois, 3 place Jean Jaures, C.S. 2903, 41029 Blois (France); Sakai, Joe [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite Francois Rabelais, Parc de Grandmont, 37200 Tours (France); Lopez, Josep Santiso [Institut de Ciencia de Materials de Barcelona, CSIC, Campus UAB, Bellaterra 08193 (Spain); Nguyen Hoa Hong [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite Francois Rabelais, Parc de Grandmont, 37200 Tours (France)], E-mail: nguyen.hoahong@univ-tours.fr

2008-04-28

Spin coated pristine TiO{sub 2} thin films show magnetic behaviors that are similar to those of pulsed laser ablated TiO{sub 2} thin films that were reported previously. It seems that in this kind of material, ferromagnetism (FM) is indeed intrinsic, and it can be achieved by various deposition techniques. The fact that oxygen annealing degrades the magnetic moment implies that the observed magnetism is likely due to defects or/and oxygen vacancies. Moreover, thick films that were deposited under the same growth conditions have the magnetic ordering degraded enormously. It is found that as for FM in undoped TiO{sub 2} films made by the chemical solution deposition, not only do defects/oxygen vacancies play a role, but also the confinement effects seem to be important.

Soft Magnetic Properties of High-Entropy Fe-Co-Ni-Cr-Al-Si Thin Films

Directory of Open Access Journals (Sweden)

Pei-Chung Lin

2016-08-01

Full Text Available Soft magnetic properties of Fe-Co-Ni-Al-Cr-Si thin films were studied. As-deposited Fe-Co-Ni-Al-Cr-Si nano-grained thin films showing no magnetic anisotropy were subjected to field-annealing at different temperatures to induce magnetic anisotropy. Optimized magnetic and electrical properties of Fe-Co-Ni-Al-Cr-Si films annealed at 200 °C are saturation magnetization 9.13 × 105 A/m, coercivity 79.6 A/m, out-of-plane uniaxial anisotropy field 1.59 × 103 A/m, and electrical resistivity 3.75 μΩ·m. Based on these excellent properties, we employed such films to fabricate magnetic thin film inductor. The performance of the high entropy alloy thin film inductors is superior to that of air core inductor.

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.

Magnetic anisotropy of thin sputtered MgB2 films on MgO substrates in high magnetic fields

Directory of Open Access Journals (Sweden)

Savio Fabretti

2014-03-01

Full Text Available We investigated the magnetic anisotropy ratio of thin sputtered polycrystalline MgB2 films on MgO substrates. Using high magnetic field measurements, we estimated an anisotropy ratio of 1.35 for T = 0 K with an upper critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear behavior, confirmed by a linear fit for magnetic fields perpendicular to the film plane. Furthermore, we observed a change of up to 12% of the anisotropy ratio in dependence of the film thickness.

Spin interference of neutrons tunneling through magnetic thin films

International Nuclear Information System (INIS)

Hino, Masahiro; Achiwa, Norio; Tasaki, Seiji; Ebisawa, Toru; Akiyoshi, Tsunekazu; Kawai, Takeshi.

1996-01-01

Larmor precession of a neutron spin is represented as the superposition of the wave functions of the two Stern-Gerlach states ↑ and ↓. A transverse neutron spin echo (NSE) spectrometer can hence be used as a neutron spin interferometer (NSI) by setting a magnetic film, such as iron and permalloy45 (Fe 55 Ni 45 ), thin enough to permit tunneling at an incident angle above and below the critical angle of the total reflection in the Larmor precession field. The NSI can be used to study spin coherent superposition and rotation of the Larmor precession through a magnetic thin film for a tunneling ↑ spin neutron and a non-tunneling ↓ spin neutron and to get the tunneling time using Larmor clock. The NSI experiments were carried out to measure the shifts of NSE signals transmitted through magnetic iron films with thicknesses of 200 and 400 A and those magnetic permalloy45 films with thicknesses of 200 and 400 A, respectively, as a function of the incident angle. Then even in tunneling ↑ spin neutron and non-tunneling ↓ spin neutron, NSE signal was observed. The phase delay was measured in iron and permalloy45 films with thickness of 200 A, and the tunneling time using Larmor clock was estimated to be 4 ± 0.6 x 10 -9 sec. (author)

Voltage control of a magnetization easy axis in piezoelectric/ferromagnetic hybrid films

International Nuclear Information System (INIS)

Kim, Sang-Koog; Lee, Jeong-Won; Shin, Sung-Chul; Song, Han Wook; Lee, Chang Ho; No, Kwangsoo

2003-01-01

We have established a spontaneous magnetization-axis switching in ferromagnetic films by applying a low voltage to a piezoelectric layer in a newly developed hybrid system comprised of the ferromagnetic and piezoelectric films. The magnetization easy axis along which a spontaneous magnetization is oriented, is readily switchable by a voltage without applying an external magnetic field through both the inverse magnetostrictive and piezoelectric effects of CoPd and lead-zirconate-titanate alloy films, respectively. This challenging work provides a new way into the memory writing as well as storage means of ultrahigh bit densities in nonvolatile magnetic random access memory

Static magnetism and thermal switching in randomly oriented L10 FePt thin films

Science.gov (United States)

Lisfi, A.; Pokharel, S.; Alqarni, A.; Akioya, O.; Morgan, W.; Wuttig, M.

2018-05-01

Static magnetism and thermally activated magnetic relaxation were investigated in granular FePt films (20 nm-200 nm thick) with random magnetic anisotropy through hysteresis loop, torque curve and magnetization time dependence measurements. While the magnetism of thicker film (200 nm thick) is dominated by a single switching of the ordered L10 phase, thinner film (20 nm) displays a double switching, which is indicative of the presence of the disordered cubic phase. The pronounced behavior of double switching in thinner film suggests that the film grain boundary is composed of soft cubic magnetic phase. The magnetic relaxation study reveals that magnetic viscosity S of the films is strongly dependent on the external applied field and exhibits a maximum value (12 kAm) around the switching field and a vanishing behavior at low (1 kOe) and large (12 kOe) fields. The activation volume of the thermal switching was found to be much smaller than the physical volume of the granular structure due to the incoherent rotation mode of the magnetization reversal mechanism, which is established to be domain wall nucleation.

High quality TmIG films with perpendicular magnetic anisotropy grown by sputtering

Science.gov (United States)

Wu, C. N.; Tseng, C. C.; Yeh, S. L.; Lin, K. Y.; Cheng, C. K.; Fanchiang, Y. T.; Hong, M.; Kwo, J.

Ferrimagnetic thulium iron garnet (TmIG) films grown on gadolinium gallium garnet substrates recently showed stress-induced perpendicular magnetic anisotropy (PMA), attractive for realization of quantum anomalous Hall effect (QAHE) of topological insulator (TI) films via the proximity effect. Moreover, current induced magnetization switching of Pt/TmIG has been demonstrated for the development of room temperature (RT) spintronic devices. In this work, high quality TmIG films (about 25nm) were grown by sputtering at RT followed by post-annealing. We showed that the film composition is tunable by varying the growth parameters. The XRD results showed excellent crystallinity of stoichiometric TmIG films with an out-of-plane lattice constant of 1.2322nm, a narrow film rocking curve of 0.017 degree, and a film roughness of 0.2 nm. The stoichiometric films exhibited PMA and the saturation magnetization at RT was 109 emu/cm3 (RT bulk value 110 emu/cm3) with a coercive field of 2.7 Oe. In contrast, TmIG films of Fe deficiency showed in-plane magnetic anisotropy. The high quality sputtered TmIG films will be applied to heterostructures with TIs or metals with strong spin-orbit coupling for novel spintronics.

Moessbauer and magnetic resonance experiments on amorphous iron-silicon films

International Nuclear Information System (INIS)

Bansal, C.; Campbell, S.J.; Stewart, A.M.

1982-01-01

Moessbauer measurements at room temperature and 4.2 K, and room temperature magnetic resonance measurments on a series of amorphous Fesub(x)Sisub(1-x) thin films (0.23 <= x <= 0.81) are presented. The concentration dependence of the isomer shifts and quadrupole splittings provides information on the nature of the local coordination in these amorphous materials. Analysis of the distributions of magnetic hyperfine splitting combined with the presence of multiple resonance in the magnetic resonance data indiates that magnetoanisotropy plays a dominant role in determining the magnetic behaviour of these films. (orig.)

The magnetic properties of amorphous and nanocrystalline cobalt-rare earth films

Science.gov (United States)

Thomas, Richard Allen

Magnetic materials are of great technological importance for their use in transformers, electric motors, computer disks and hard drives, etc. Understanding the intrinsic physical properties of magnetic materials is essential in order to develop new and better materials for these applications. Presented here is a study of the magnetic properties of amorphous and nanocrystalline cobalt-rare earth (Co-R, where R = Y, Pr, Gd, and Dy) films composed of very small crystalline grains, about 2--200 nm in size. The films are produced by co-sputtering two single element targets onto a single substrate. Many are then annealed briefly to produce magnetic films composed of nanoscale crystallites. The magnetic properties of these films depend largely on the relative strengths of the exchange interaction, which tends to align the spins within a group of crystallites, and the magnetocrystalline anisotropy, which tends to align the spins within each crystallite to an easy direction defined by the crystal lattice. The ratio of these two competing interactions varies strongly with grain size as predicted by the random magnetic anisotropy model. The coercivity, remanent magnetization, initial magnetization, etc., are discussed in light of the predictions made by the models of Callen et al (1977), Chi and Alben (1977), Chudnovsky (1986), and Fukunaga and Inoue (1992).

Piezoelectric response of a PZT thin film to magnetic fields from permanent magnet and coil combination

Science.gov (United States)

Guiffard, B.; Seveno, R.

2015-01-01

In this study, we report the magnetically induced electric field E 3 in Pb(Zr0.57Ti0.43)O3 (PZT) thin films, when they are subjected to both dynamic magnetic induction (magnitude B ac at 45 kHz) and static magnetic induction ( B dc) generated by a coil and a single permanent magnet, respectively. It is found that highest sensitivity to B dc——is achieved for the thin film with largest effective electrode. This magnetoelectric (ME) effect is interpreted in terms of coupling between eddy current-induced Lorentz forces (stress) in the electrodes of PZT and piezoelectricity. Such coupling was evidenced by convenient modelling of experimental variations of electric field magnitude with both B ac and B dc induction magnitudes, providing imperfect open circuit condition was considered. Phase angle of E 3 versus B dc could also be modelled. At last, the results show that similar to multilayered piezoelectric-magnetostrictive composite film, a PZT thin film made with a simple manufacturing process can behave as a static or dynamic magnetic field sensor. In this latter case, a large ME voltage coefficient of under B dc = 0.3 T was found. All these results may provide promising low-cost magnetic energy harvesting applications with microsized systems.

Magnetic properties of Cobalt thin films deposited on soft organic layers

Energy Technology Data Exchange (ETDEWEB)

Bergenti, I. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy)]. E-mail: i.bergenti@bo.ismn.cnr.it; Riminucci, A. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy); Arisi, E. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy); Murgia, M. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy); Cavallini, M. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy); Solzi, M. [Dipartimento di Fisica dell' Universita di Parma and CNISM, Parco Area delle Scienze 7/A, Parma 43100 (Italy); Casoli, F. [IMEM-CNR Parco Area delle Scienze 37/A, Parma 43100 (Italy); Dediu, V. [ISMN-CNR via P. Gobetti 101, Bologna 40129 (Italy)

2007-09-15

Magnetic and morphological properties of Cobalt thin films grown by RF sputtering on organic Alq3 layers were investigated by magneto-optical Kerr effect (MOKE) technique and atomic force microscopy (AFM). The AFM images indicate a template growth of Co layers on top of Alq3, the magnetic film 'decorates' the surface of organic material. This peculiar morphology induces a strong uniaxial magnetic anisotropy in the Co films, as detected by MOKE measurements. Results are important for the operation of a new class of devices-vertical organic spin valves.

Defect characterization and magnetic properties in un-doped ZnO thin film annealed in a strong magnetic field

International Nuclear Information System (INIS)

Ning Shuai; Zhan Peng; Wang Wei-Peng; Li Zheng-Cao; Zhang Zheng-Jun

2014-01-01

Highly c-axis oriented un-doped zinc oxide (ZnO) thin films, each with a thickness of ∼ 100 nm, are deposited on Si (001) substrates by pulsed electron beam deposition at a temperature of ∼ 320 °C, followed by annealing at 650 °C in argon in a strong magnetic field. X-ray photoelectron spectroscopy (XPS), positron annihilation analysis (PAS), and electron paramagnetic resonance (EPR) characterizations suggest that the major defects generated in these ZnO films are oxygen vacancies. Photoluminescence (PL) and magnetic property measurements indicate that the room-temperature ferromagnetism in the un-doped ZnO film originates from the singly ionized oxygen vacancies whose number depends on the strength of the magnetic field applied in the thermal annealing process. The effects of the magnetic field on the defect generation in the ZnO films are also discussed. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Effects of magnetic flux densities on microstructure evolution and magnetic properties of molecular-beam-vapor-deposited nanocrystalline Fe_3_0Ni_7_0 thin films

International Nuclear Information System (INIS)

Cao, Yongze; Wang, Qiang; Li, Guojian; Ma, Yonghui; Du, Jiaojiao; He, Jicheng

2015-01-01

Nanocrystalline Fe_3_0Ni_7_0 (in atomic %) thin films were prepared by molecular-beam-vapor deposition in magnetic fields with different magnetic flux densities. The microstructure evolution of these thin films was studied by atomic force microscopy, transmission electron microscopy, and high resolution transmission electron microscopy; the soft magnetic properties were examined by vibrating sample magnetometer at room temperature. The results show that all our Fe_3_0Ni_7_0 thin films feature an fcc single-phase structure. With increasing magnetic flux density, surface roughness, average particle size and grain size of the thin films decreased, and the short-range ordered clusters (embryos) of thin films increased. Additionally, the magnetic anisotropy in the in-plane and the coercive forces of the thin films gradually reduced with increasing magnetic flux density. - Highlights: • With increasing magnetic flux density, average particle size of films decreased. • With increasing magnetic flux density, surface roughness of thin films decreased. • With increasing magnetic flux density, short-range ordered clusters increased. • With increasing magnetic flux density, the coercive forces of thin films reduced. • With increasing magnetic flux density, soft magnetic properties are improved.

Structure and magnetization in CoPd thin films and nanocontacts

International Nuclear Information System (INIS)

Morgan, Caitlin; Schmalbuch, Klaus; García-Sánchez, Felipe; Schneider, Claus M.; Meyer, Carola

2013-01-01

We present results showing the structural and magnetic properties of MBE-grown extended films and nanostructured elements of various CoPd alloys. X-ray diffraction studies show that the thin films are polycrystalline, yet exhibit a strong preferential growth orientation along the (111) direction. Magnetic force microscopy and SQUID are used to gain an understanding of the magnetic behavior of the CoPd system with respect to competing anisotropy contributions, based on temperature-dependent SQUID data, collected between 4 and 300 K. The idea and potential implications of using CoPd as a contact material to achieve spin injection in carbon nanotube-based devices is discussed. - Highlights: ► In-plane magnetization of CoPd films increases with added Co content. ► Quasi single-domain nanostructures of Co 50 Pd 50 exhibit almost no OOP component. ► Nanostructures exhibit decrease in coercive field with initial temperature decrease. ► Magnetic behavior is influenced by the anti-FM oxide and magnetoelastic effect.

Magnetic properties and high frequency characteristics of FeCoN thin films

Directory of Open Access Journals (Sweden)

Tae-Jong Hwang

2016-05-01

Full Text Available (Fe65Co35N soft magnetic thin films were prepared by reactive RF magnetron sputtering with the sputtering power of 100 W on thermally oxidized Si substrate in various nitrogen partial pressures (PN2. A strong uniaxial in-plane magnetic anisotropy with the easy-axis coercive field as low as 1∼2 Oe was observed in films grown at PN2 in the range from 3.3% to 5.5%. The saturation magnetizations for those films were about 20 KG. Outside this range, almost isotropic magnetization curves were observed. Vector network analyzer and grounded coplanar waveguide were used to measure the ferromagnetic resonance (FMR signals up to 25 GHz. The FMR signals were detected only in anisotropic films and their FMR frequencies were well fit to the Kittel formula. The obtained g-values and damping parameters at magnetic fields >20 kOe for films grown at PN2 of 3.3%, 4.8% and 5.5% were 1.96, 1.86, 1.92 and 0.0055, 0.0047, 0.0046, respectively. This low damping factor qualifies FeCoN thin films for high-frequency applications.

Tailoring of in-plane magnetic anisotropy in polycrystalline cobalt thin films by external stress

Energy Technology Data Exchange (ETDEWEB)

Kumar, Dileep, E-mail: dkumar@csr.res.in [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Singh, Sadhana [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Vishawakarma, Pramod [School of Nanotechnology, RGPV, Bhopal 462036 (India); Dev, Arun Singh; Reddy, V.R. [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Gupta, Ajay [Amity Center for Spintronic Materials, Amity University, Sector 125, Noida 201303 (India)

2016-11-15

Polycrystalline Co films of nominal thickness ~180 Å were deposited on intentionally curved Si substrates. Tensile and compressive stresses of 100 MPa and 150 MPa were induced in the films by relieving the curvature. It has been found that, within the elastic limit, presence of stress leads to an in-plane magnetic anisotropy in the film and its strength increases with increasing stress. Easy axis of magnetization in the films is found to be parallel/ transverse to the compressive /tensile stresses respectively. The origin of magnetic anisotropy in the stressed films is understood in terms of magneto- elastic coupling, where the stress try to align the magnetic moments in order to minimize the magneto-elastic as well as anisotropy energy. Tensile stress is also found to be responsible for the surface smoothening of the films, which is attributed to the movement of the atoms associated with the applied stress. The present work provides a possible way to tailor the magnetic anisotropy and its direction in polycrystalline and amorphous films using external stress. - Highlights: • Tensile and compressive stresses were induced in Co films by removing the bending force from the substrates after film deposition. • Controlled external mechanical stress is found to be responsible for magnetic anisotropies in amorphous and polycrystalline thin films, where crystalline anisotropy is absent. • Tensile stress leads to surface smoothening of the polycrystalline Co films.

Magnetic and structural properties of NdFeB thin film prepared by step annealing

International Nuclear Information System (INIS)

Serrona, Leo K.E.B.; Sugimura, A.; Fujisaki, R.; Okuda, T.; Adachi, N.; Ohsato, H.; Sakamoto, I.; Nakanishi, A.; Motokawa, M.

2003-01-01

The crystallization of the amorphous phase into the tetragonal Nd 2 Fe 14 B (PHI) phase and the corresponding changes in magnetic properties have been examined by step annealing experiment using a 2 μm thick NdFeB film sample. Microstructural and magnetic analysis indicate that the film was magnetically soft as deposited with the coercivity H ciperp -1 and the remnant magnetization 4πM rperp -1 was developed and diffraction analysis showed evidence of PHI phase 002l peaks being aligned perpendicular to the film plane. At an optimum annealing temperature of 575 deg. C, the remnant magnetization of this anisotropic thin film is around 0.60 T with intrinsic coercivity of ∼1340 kA m -1 . Annealing the film sample at 200 deg. C≤T ann ≤750 deg. C showed variations in magnetic properties that were mostly due to the change in the perpendicular anisotropy. Based on 4πM sperpendicular values plotted against T ann , a dip in 4πM sperpendicular values was observed as T ann increased in the soft-to-hard magnetic characteristics transition region and rose as the hard crystalline phase started to form. The results show that the magnetic properties of the NdFeB film were slightly influenced by the presence of NdO, film surface roughening and the small increase in crystal size as a consequence of repeated heat treatment. At T ann ∼300 deg. C, the nominal saturation magnetization indicated a certain degree of weak perpendicular magnetic anisotropy in the film sample considered to be essential in the enhancement of coercivity in crystallized films

Effect of recording condition on the diffraction efficiency of magnetic hologram with magnetic garnet films

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Yuichi, E-mail: nakamura@ee.tut.ac.jp; Takagi, Hiroyuki; Lim, Pang Boey; Inoue, Mitsuteru [Department of Electrical and Electronic Engineering, Toyohashi University of Technology, 1-1 Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)

2014-09-14

A holographic memory has been attracting attention as recording media with high recording density and high data transfer rate. We have studied the magnetic garnets as a rewritable and long life media for magnetic holography. However, since the signal intensity of reconstructed image was relatively low, the effects of recording conditions on the diffraction efficiency of magnetic hologram were investigated with experiments and the numerical simulation using COMSOL multi-physics. The diffraction efficiency tends to decrease as increasing the spatial frequency, and the use of short pulse laser with the pulse width of 50 ps was found to be effective to achieve high diffraction efficiency. This suggests that the formation of clear magnetic fringe similar to interference pattern can be obtained by the use of short pulse laser since undesirable heat diffusion during radiation does not occur. On the other hand, the diffraction efficiency increased as increasing the film thickness up to 3.1 μm but was saturated in the garnet film thicker than 3.1 μm in the case of spatial frequency of 1500 line pair/mm. The numerical simulation showed that the effective depth of magnetic fringe was limited about 1.8 μm irrespective of the garnet film thickness because the fringes were connected by thermal diffusion near the surface of the film, and the effective depth is limited due to this connection of the magnetic fringe. Avoiding this fringe connection, much higher diffraction efficiency will be achieved.

Refraction of polarized neutrons on the boundary in thick magnetic film FeAlSi

Energy Technology Data Exchange (ETDEWEB)

Aksenov, V L; Kozhevnikov, S V; Nikitenko, Yu V [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Frank Lab. of Neutron Physics

1999-07-01

Complete text of publication follows. Refraction of polarized neutrons in multilayer structure FeAlSi(20 mkm)/Cr(0.05 mkm)/CaTiO{sub 3}(1000 mkm) has been investigated. An external magnetic field was applied under an angle to the sample surface. Refraction on themagnetic boundaries of two types has been investigated. First type is the boundary vacuum-magnetic film. Second type is magnetic film - non-magnetic substrate CaTiO{sub 3} (thin non-magnetic Cr layer doesn't refract the beam). On the boundary there are spin-flip and beam-splitting. Four spatial splitted beams were observed for different spin transitions on each type of the boundary: '+-', '++', '-+' and '--'. From the experimental values of the glancing angles of refracted beam the following parameters has been derives: the nuclear potentials of the magnetic film and the non-magnetic substrate, the magnitude and the direction of a magnetic induction in the magnetic film. It has been shown that the method of refractometry of polarized neutrons can be used for investigation of thick (about mkm) magnetic films. (author)

Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

DEFF Research Database (Denmark)

Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.

2002-01-01

In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...... the Gd and Y stearate LB films. Placing the small BDPA crystal on the film surface we have found that for the Gd LB sample the effective g-value of the radical's resonance depends on the film orientation in respect to the external magnetic field direction. The relative shift of the EPR signal...

Magnetic vortex state and multi-domain pattern in electrodeposited hemispherical nanogranular nickel films

International Nuclear Information System (INIS)

Samardak, Alexander; Sukovatitsina, Ekaterina; Ognev, Alexey; Stebliy, Maksim; Davydenko, Alexander; Chebotkevich, Ludmila; Keun Kim, Young; Nasirpouri, Forough; Janjan, Seyed-Mehdi; Nasirpouri, Farzad

2014-01-01

Magnetic states of nickel nanogranular films were studied in two distinct structures of individual and agglomerated granules electrodeposited on n-type Si(1 1 1) surface from a modified Watts bath at a low pH of 2. Magnetic force microscopy and micromagnetic simulations revealed three-dimensional out-of-plane magnetic vortex states in stand-alone hemispherical granules and their arrays, and multi-domain patterns in large agglomerates and integrated films. Once the granules coalesce into small chains or clusters, the coercivity values increased due to the reduction of inter-granular spacing and strengthening of the magnetostatic interaction. Further growth leads to the formation of a continuous granulated film which strongly affected the coercivity and remanence. This was characterized by the domain wall nucleation and propagation leading to a stripe domain pattern. Magnetoresistance measurements as a function of external magnetic field are indicative of anisotropic magnetoresistance (AMR) for the continuous films electrodeposited on Si substrate. - Highlights: • Magnetic states of electrodeposited nickel in isolated spherical and agglomerated nanogranules, and a continuous film. • Preferential magnetization reversal mechanism in isolated granules is vortex state. • Micromagnetic simulations confirm the three-dimensional vortex. • Transition between the vortex state and multi-domain magnetic pattern causes a significant decrease in the coercive force. • Continuous nickel films electrodeposited on silicon substrate exhibit AMR whose magnitude increases with the film thickness

Single-molecule magnets on a polymeric thin film as magnetic quantum bits

Science.gov (United States)

Ruiz-Molina, Daniel; Gomez, Jordi; Mas-Torrent, Marta; Balana, Ana Isabel; Domingo, Nues; Tejada, Javier; Martinez, Maria Teresa; Rovira, Concepcio; Veciana, Jaume

2003-04-01

Single-molecule magnets (SMM) have a large-spin ground state with appreciable magnetic anisotropy, resulting in a barrier for the spin reversal As a consequence, interesting magnetic properties such as out-of-phase ac magnetic susceptibility signals and stepwise magnetization hysteresis loops are observed. In addition to resonant magnetization tunnelling, during the last few years several other interesting phenomena have also been reported. The origin of the slow magnetization relaxation rates as well as of other phenomena are due to individual molecules rather than to long-range ordering; as confirmed by magnetization relaxation and heat capacity studies. Therefore, SMM represent nanoscale magnetic particles of a sharply defined size that offer the potential access to the ultimate high-density information storage devices as well as for quantum computing applications. However, if a truly molecular computational device based on SMM is to be achieved, new systematic studies that allow us to find a proper way to address properly oriented individual molecules or molecular aggregates onto the surface of a thin film, where each molecule or molecular aggregate can be used as a bit of information, are highly required. Here we report a new soft, reliable and simple methodology to address individual Mn12 molecules onto a film surface, as revealed by Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM) images. Moreover, the advantageous properties of polymeric matrices, such as flexibility, transparency and low density, make this type of materials very interesting for potential applications.

Spontaneous phase transitions in magnetic films with a modulated structure

International Nuclear Information System (INIS)

Arzamastseva, G. V.; Evtikhov, M. G.; Lisovskii, F. V.; Mansvetova, E. G.

2011-01-01

The influence of monoperiodic and biperiodic bias fields on the nucleation of domain structures in quasi-uniaxial magnetic films near the Curie point has been studied experimentally. The main types of observed nonuniform magnetic moment distributions have been established and chains of a devil’s staircase phase transitions are shown to be realized when the films are slowly cooled.

Magnetic anisotropies of (Ga,Mn)As films and nanostructures

Energy Technology Data Exchange (ETDEWEB)

Hoffmann, Frank

2011-02-02

In this work the magnetic anisotropies of the diluted magnetic semiconductor (Ga,Mn)As were investigated experimentally. (Ga,Mn)As films show a superposition of various magnetic anisotropies which depend sensitively on various parameters such as temperature, carrier concentration or lattice strain. However, the anisotropies of lithographically prepared (Ga,Mn)As elements differ significantly from an unpatterned (Ga,Mn)As film. In stripe-shaped structures this behaviour is caused by anisotropic relaxation of the compressive lattice strain. In order to determine the magnetic anisotropies of individual (Ga,Mn)As nanostructures a combination of ferromagnetic resonance and time-resolved scanning Kerr microscopy was employed in this thesis. In addition, local changes of the magnetic anisotropy in circular and rectangular structures were visualized by making use of spatially resolved measurements. Finally, also the influence of the laterally inhomogeneous magnetic anisotropies on the static magnetic properties, such as coercive fields, was investigated employing spatially resolved static MOKE measurements on individual (Ga,Mn)As elements. (orig.)

Defect-induced magnetic order in pure ZnO films

Science.gov (United States)

Khalid, M.; Ziese, M.; Setzer, A.; Esquinazi, P.; Lorenz, M.; Hochmuth, H.; Grundmann, M.; Spemann, D.; Butz, T.; Brauer, G.; Anwand, W.; Fischer, G.; Adeagbo, W. A.; Hergert, W.; Ernst, A.

2009-07-01

We have investigated the magnetic properties of pure ZnO thin films grown under N2 pressure on a -, c -, and r -plane Al2O3 substrates by pulsed-laser deposition. The substrate temperature and the N2 pressure were varied from room temperature to 570°C and from 0.007 to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c - and a -plane Al2O3 substrates did not show significant ferromagnetism. However, ZnO films grown on r -plane Al2O3 showed reproducible ferromagnetism at 300 K when grown at 300-400°C and 0.1-1.0 mbar N2 pressure. Positron annihilation spectroscopy measurements as well as density-functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

Defect characterization and magnetic properties in un-doped ZnO thin film annealed in a strong magnetic field

Science.gov (United States)

Ning, Shuai; Zhan, Peng; Wang, Wei-Peng; Li, Zheng-Cao; Zhang, Zheng-Jun

2014-12-01

Highly c-axis oriented un-doped zinc oxide (ZnO) thin films, each with a thickness of ~ 100 nm, are deposited on Si (001) substrates by pulsed electron beam deposition at a temperature of ~ 320 °C, followed by annealing at 650 °C in argon in a strong magnetic field. X-ray photoelectron spectroscopy (XPS), positron annihilation analysis (PAS), and electron paramagnetic resonance (EPR) characterizations suggest that the major defects generated in these ZnO films are oxygen vacancies. Photoluminescence (PL) and magnetic property measurements indicate that the room-temperature ferromagnetism in the un-doped ZnO film originates from the singly ionized oxygen vacancies whose number depends on the strength of the magnetic field applied in the thermal annealing process. The effects of the magnetic field on the defect generation in the ZnO films are also discussed.

Nanocrystalline iron nitride films with perpendicular magnetic anisotropy

International Nuclear Information System (INIS)

Gupta, Ajay; Dubey, Ranu; Leitenberger, W.; Pietsch, U.

2008-01-01

Nanocrystalline α-iron nitride films have been prepared using reactive ion-beam sputtering. Films develop significant perpendicualr magnetic anisotropy (PMA) with increasing thickness. A comparison of x-ray diffraction patterns taken with scattering vectors in the film plane and out of the film plane provides a clear evidence for development of compressive strain in the film plane with thickness. Thermal annealing results in relaxation of the strain, which correlates very well with the relaxation of PMA. This suggests that the observed PMA is a consequence of the breaking of the symmetry of the crystal structure due to the compressive strain

Modulation of magnetic coercivity in Ni thin films by reversible control of strain

Energy Technology Data Exchange (ETDEWEB)

Lin, Wen-Chin, E-mail: wclin@ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Huang, Chia-Wei; Ting, Yi-Chieh; Lo, Fang-Yuh [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Chern, Ming-Yau [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

2015-05-01

In this study, we demonstrated the magnetoelectric control of magnetic thin films. (111)-textured Pd/Ni/Pd thin films were prepared on mica/lead zirconium titanate (PZT) substrates for the investigation. The reversible modulation of magnetic coercivity in Ni films was observed through the electric-voltage-controlled strain variation from the PZT substrate. For 14 nm Ni film, the applied electric field of ±350 V/m led to ±0.5% strain variation of PZT, which was transferred to ±0.4% strain variation of Pd/Ni/Pd thin films on mica, and resulted in ∓17 Oe (∓5% of the preliminary magnetic coercivity). The reversible modulation of magnetic coercivity is supposed to be caused by the voltage-controlled strain through the magneto-elastic effect. - Highlights: • The magnetoelectric control of the magnetic coercivity of Pd/Ni/Pd thin films was demonstrated. • The ±0.4% strain variation of 14 nm Ni thin films resulted in ±17 Oe change of H{sub c}. • The reversible modulation of H{sub c} is supposed to be caused by the magneto-elastic effect.

Magnetic Property in Large Array Niobium Antidot Thin Films

Science.gov (United States)

Tinghui, Chen; Hsiang-Hsi, Kung; Wei-Li, Lee; Institute of Physics, Academia Sinica, Taipei, Taiwan Team

2014-03-01

In a superconducting ring, the total flux inside the ring is required to be an integer number of the flux quanta. Therefore, a supercurrent current can appear within the ring in order to satisfy this quantization rule, which gives rise to certain magnetic response. By using a special monolayer polymer/nanosphere hybrid we developed previously, we fabricated a series of superconducting niobium antidot thin films with different antidot diameters. The antidots form well-ordered triangular lattice with a lattice spacing about 200 nm and extend over an area larger than 1 cm2, which enables magnetic detections simply by a SQUID magnetometer. We observed magnetization oscillation with external magnetic field due to the supercurrent screening effect, where different features for large and small antidot thin films were found. Detailed size and temperature dependencies of the magnetization in niobium antidot nanostructures will be presented.

Magnetic hysteresis of cerium doped bismuth ferrite thin films

International Nuclear Information System (INIS)

Gupta, Surbhi; Tomar, Monika; Gupta, Vinay

2015-01-01

The influence of Cerium doping on the structural and magnetic properties of BiFeO 3 thin films have been investigated. Rietveld refinement of X-ray diffraction data and successive de-convolution of Raman scattering spectra of Bi 1−x Ce x FeO 3 (BCFO) thin films with x=0–0.20 reflect the single phase rhombohedral (R3c) formation for x<0.08, whereas concentration-driven gradual structural phase transition from rhombohedral (R3c) to partial tetragonal (P4mm) phase follows for x≥0.08. All low wavenumber Raman modes (<300 cm −1 ) showed a noticeable shift towards higher wavenumber with increase in doping concentration, except Raman E-1 mode (71 cm −1 ), shows a minor shift. Sudden evolution of Raman mode at 668 cm −1 , manifested as A 1 -tetragonal mode, accompanied by the shift to higher wavenumber with increase in doping concentration (x) affirm partial structural phase transition. Anomalous wasp waist shaped (M–H) hysteresis curves with improved saturation magnetization (M s ) for BCFO thin films is attributed to antiferromagnetic interaction/hybridization between Ce 4f and Fe 3d electronic states. The contribution of both hard and soft phase to the total coercivity is calculated. Polycrystalline Bi 0.88 Ce 0.12 FeO 3 thin film found to exhibit better magnetic properties with M s =15.9 emu/g without any impure phase. - Highlights: • Synthesis of single phase Bi 1−x Ce x FeO 3 thin films with (x=0–0.2) on cost effective corning glass and silicon substrates using CSD technique. • Structural modification studies using Rietveld refinement of XRD and de-convolution of Raman spectra revealed partial phase transition from rhombohedral (R3c) to tetragonal (P4mm) phase. • Possible reasons for origin of pinched magnetic behavior of BCFO thin films are identified. • Contribution of both hard and soft magnetic phase in coercivity of BCFO thin films is calculated and practical applications of such materials exhibiting pinching behavior are conferred

Magnetic hysteresis of cerium doped bismuth ferrite thin films

Energy Technology Data Exchange (ETDEWEB)

Gupta, Surbhi [Department of Physics and Astrophysics, University of Delhi (India); Tomar, Monika [Physics Department, Miranda House, University of Delhi (India); Gupta, Vinay, E-mail: drguptavinay@gmail.com [Department of Physics and Astrophysics, University of Delhi (India)

2015-03-15

The influence of Cerium doping on the structural and magnetic properties of BiFeO{sub 3} thin films have been investigated. Rietveld refinement of X-ray diffraction data and successive de-convolution of Raman scattering spectra of Bi{sub 1−x}Ce{sub x}FeO{sub 3} (BCFO) thin films with x=0–0.20 reflect the single phase rhombohedral (R3c) formation for x<0.08, whereas concentration-driven gradual structural phase transition from rhombohedral (R3c) to partial tetragonal (P4mm) phase follows for x≥0.08. All low wavenumber Raman modes (<300 cm{sup −1}) showed a noticeable shift towards higher wavenumber with increase in doping concentration, except Raman E-1 mode (71 cm{sup −1}), shows a minor shift. Sudden evolution of Raman mode at 668 cm{sup −1}, manifested as A{sub 1}-tetragonal mode, accompanied by the shift to higher wavenumber with increase in doping concentration (x) affirm partial structural phase transition. Anomalous wasp waist shaped (M–H) hysteresis curves with improved saturation magnetization (M{sub s}) for BCFO thin films is attributed to antiferromagnetic interaction/hybridization between Ce 4f and Fe 3d electronic states. The contribution of both hard and soft phase to the total coercivity is calculated. Polycrystalline Bi{sub 0.88}Ce{sub 0.12}FeO{sub 3} thin film found to exhibit better magnetic properties with M{sub s}=15.9 emu/g without any impure phase. - Highlights: • Synthesis of single phase Bi{sub 1−x}Ce{sub x}FeO{sub 3} thin films with (x=0–0.2) on cost effective corning glass and silicon substrates using CSD technique. • Structural modification studies using Rietveld refinement of XRD and de-convolution of Raman spectra revealed partial phase transition from rhombohedral (R3c) to tetragonal (P4mm) phase. • Possible reasons for origin of pinched magnetic behavior of BCFO thin films are identified. • Contribution of both hard and soft magnetic phase in coercivity of BCFO thin films is calculated and practical

Optical and magnetic properties of a transparent garnet film for atomic physics experiments

Directory of Open Access Journals (Sweden)

Mari Saito

2016-12-01

Full Text Available We investigated the optical and magnetic properties of a transparent magnetic garnet with a particular focus on its applications to atomic physics experiments. The garnet film used in this study was a magnetically soft material that was originally designed for a Faraday rotator at optical communication wavelengths in the near infrared region. The film had a thickness of 2.1 μm and a small optical loss at a wavelength of λ=780 nm resonant with Rb atoms. The Faraday effect was also small and, thus, barely affected the polarization of light at λ=780 nm. In contrast, large Faraday rotation angles at shorter wavelengths enabled us to visualize magnetic domains, which were perpendicularly magnetized in alternate directions with a period of 3.6 μm. We confirmed the generation of an evanescent wave on the garnet film, which can be used for the optical observation and manipulation of atoms on the surface of the film. Finally, we demonstrated a magnetic mirror for laser-cooled Rb atoms using the garnet film.

Temperature dependent magnetic coupling between ferromagnetic FeTaC layers in multilayer thin films

International Nuclear Information System (INIS)

Singh, Akhilesh Kumar; Hsu, Jen-Hwa; Perumal, Alagarsamy

2016-01-01

We report systematic investigations on temperature dependent magnetic coupling between ferromagnetic FeTaC layers and resulting magnetic properties of multilayer structured [FeTaC (~67 nm)/Ta(x nm)] 2 /FeTaC(~67 nm)] thin films, which are fabricated directly on thermally oxidized Si substrate. As-deposited amorphous films are post annealed at different annealing temperatures (T A =200, 300 and 400 °C). Structural analyzes reveal that the films annealed at T A ≤200 °C exhibit amorphous nature, while the films annealed above 200 °C show nucleation of nanocrystals at T A =300 °C and well-defined α-Fe nanocrystals with size of about 9 nm in amorphous matrix for 400 °C annealed films. Room temperature and temperature dependent magnetic hysteresis (M–H) loops reveal that magnetization reversal behaviors and magnetic properties are strongly depending on spacer layer thickness (x), T A and temperature. A large reduction in coercivity (H C ) was observed for the films annealed at 200 °C and correlated to relaxation of stress quenched in during the film deposition. On the other hand, the films annealed at 300 °C exhibit unusual variation of H C (T), i.e., a broad minimum in H C (T) vs T curve. This is caused by change in magnetic coupling between ferromagnetic layers having different microstructure. In addition, the broad minimum in the H C (T) curve shifts from 150 K for x=1 film to 80 K for x=4 film. High-temperature thermomagnetization data show a strong (significant) variation of Curie temperature (T C ) with T A (x). The multilayer films annealed at 200 °C exhibit low value of T C with a minimum of 350 K for x=4 film. But, the films annealed at 400 °C show largest T C with a maximum of 869 K for x=1 film. The observed results are discussed on the basis of variations in magnetic couplings between FeTaC layers, which are majorly driven by temperature, spacer layer thickness, annealing temperature and nature of interfaces. - Highlights: • Preparation and

Preparation and influence of pH on the dynamic magnetic property of magnetic FeCoC films

Energy Technology Data Exchange (ETDEWEB)

Feng, Hongmei; Wei, Jinwu; Zhu, Zengtai; Cao, Derang; Liu, Qingfang [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang, Jianbo, E-mail: wangjb@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Special Function Materials and Structural Design of the Ministry of the Education, Lanzhou University, Lanzhou 730000 (China)

2016-07-01

FeCoC films were successfully prepared by electrochemical deposition method in different citric acid concentrations and pH values. The morphology, structure and magnetic properties were investigated. FeCoC films deposited at different citric acid concentrations have good soft magnetic performance. As the pH value increases from 2.49 to 6.02, the atomic ratio of Fe:Co range from 0.72 to 0.95. The coercivities of the films deposited at different pH values first increase and then decrease with increasing pH. The resonance frequency of the films can be tuned by controlling the pH value, and in an appropriate pH value a wide absorption peak can be obtained. - Highlights: • We have successfully prepared FeCoC soft magnetic films by electrochemical deposition method. • The resonance frequency can be controlled by changing pH value. • A widely absorption peak will be obtained when the pH value is appropriate.

Structure and magnetization in CoPd thin films and nanocontacts

Energy Technology Data Exchange (ETDEWEB)

Morgan, Caitlin, E-mail: c.morgan@fz-juelich.de [Peter Gruenberg Institut, Forschungszentrum Juelich (Germany); JARA Juelich Aachen Research Alliance, 52425 Juelich (Germany); Schmalbuch, Klaus [JARA Juelich Aachen Research Alliance, 52425 Juelich (Germany); Physikalisches Institut, RWTH Aachen University, Otto-Blumenthal-Strasse, 52074 Aachen (Germany); Garcia-Sanchez, Felipe [Peter Gruenberg Institut, Forschungszentrum Juelich (Germany); JARA Juelich Aachen Research Alliance, 52425 Juelich (Germany); Schneider, Claus M. [Peter Gruenberg Institut, Forschungszentrum Juelich (Germany); JARA Juelich Aachen Research Alliance, 52425 Juelich (Germany); Fakultaet f. Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, D-47048 Duisburg (Germany); Meyer, Carola [Peter Gruenberg Institut, Forschungszentrum Juelich (Germany); JARA Juelich Aachen Research Alliance, 52425 Juelich (Germany)

2013-01-15

We present results showing the structural and magnetic properties of MBE-grown extended films and nanostructured elements of various CoPd alloys. X-ray diffraction studies show that the thin films are polycrystalline, yet exhibit a strong preferential growth orientation along the (111) direction. Magnetic force microscopy and SQUID are used to gain an understanding of the magnetic behavior of the CoPd system with respect to competing anisotropy contributions, based on temperature-dependent SQUID data, collected between 4 and 300 K. The idea and potential implications of using CoPd as a contact material to achieve spin injection in carbon nanotube-based devices is discussed. - Highlights: Black-Right-Pointing-Pointer In-plane magnetization of CoPd films increases with added Co content. Black-Right-Pointing-Pointer Quasi single-domain nanostructures of Co{sub 50}Pd{sub 50} exhibit almost no OOP component. Black-Right-Pointing-Pointer Nanostructures exhibit decrease in coercive field with initial temperature decrease. Black-Right-Pointing-Pointer Magnetic behavior is influenced by the anti-FM oxide and magnetoelastic effect.

Strain Induced Magnetism in SrRuO3 Epitaxial Thin Films

Energy Technology Data Exchange (ETDEWEB)

Grutter, A.; Wong, F.; Arenholz, E.; Liberati, M.; Suzuki, Y.

2010-01-10

Epitaxial SrRuO{sub 3} thin films were grown on SrTiO{sub 3}, (LaAlO{sub 3}){sub 0.3}(SrAlO{sub 3}){sub 0.7} and LaAlO{sub 3} substrates inducing different biaxial compressive strains. Coherently strained SrRuO{sub 3} films exhibit enhanced magnetization compared to previously reported bulk and thin film values of 1.1-1.6 {micro}{sub B} per formula unit. A comparison of (001) and (110) SrRuO{sub 3} films on each substrate indicates that films on (110) oriented have consistently higher saturated moments than corresponding (001) films. These observations indicate the importance of lattice distortions in controlling the magnetic ground state in this transitional metal oxide.

High-coercive garnet films for thermo-magnetic recording

International Nuclear Information System (INIS)

Berzhansky, V N; Danishevskaya, Y V; Nedviga, A S; Milyukova, H T

2016-01-01

The possibility of using high-coercive of garnet films for thermo-magnetic recording is related with the presence of the metastable domain structure, which arises due to a significant mismatch of the lattice parameters of the film and the substrate. In the work the connection between facet crystal structure of elastically strained ferrite garnets films and the domain structure in them is established by methods of phase contrast and polarization microscopy. (paper)

Evaluation of the magnetic and mechanical properties of reactor pressure vessel steels by incremental permeability change curve measurements

International Nuclear Information System (INIS)

Ebine, N.; Suzuki, M.

2001-01-01

Incremental permeability measurement was performed for two types of structural steels along with the magnetization of their hysteresis minor-loop. The obtained incremental permeability change curve has two sharp peaks, and the width between the two peaks is correlated with the coercivity. Hence the existence of good correlation was verified. On the basis of this result, nondestructive measurement experiments were carried out with planar coils to evaluate changes in the material properties of ferromagnetic structural steel plates. Changes in output voltages from planar coils with different test plates were correlated with their mechanical and magnetic properties. The correlation is so good that the measurement method adopted in this work could be used for nondestructive evaluation of material degradation in ferromagnetic structural steels. (author)

The correlation between mechanical stress and magnetic anisotropy in ultrathin films

International Nuclear Information System (INIS)

Sander, D.

1999-01-01

The impact of stress-driven structural transitions and of film strain on the magnetic properties of nm ferromagnetic films is discussed. The stress-induced bending of film-substrate composites is analysed to derive information on film stress due to lattice mismatch or due to surface-stress effects. The magneto-elastic coupling in epitaxial films is determined directly from the magnetostrictive bending of the substrate. The combination of stress measurements with magnetic investigations by the magneto-optical Kerr effect (MOKE) reveals the modification of the magnetic anisotropy by film stress. Stress-strain relations are derived for various epitaxial orientations to facilitate the analysis of the substrate curvature. Biaxial film stress and magneto-elastic coupling coefficients are measured in epitaxial Fe films in situ on W single-crystal substrates. Tremendous film stress of more than 10 GPa is measured in pseudomorphic Fe layers, and the important role of film stress as a driving force for the formation of misfit distortions and for inducing changes of the growth mode in monolayer thin films is presented. The direct measurement of the magneto-elastic coupling in epitaxial films proves that the magnitude and sign of the magneto-elastic coupling deviate from the respective bulk value. Even a small film strain of order 0.1% is found to induce a significant change of the effective magneto-elastic coupling coefficient. This peculiar behaviour is ascribed to a second-order strain dependence of the magneto-elastic energy density, in contrast to the linear strain dependence that is valid for bulk samples. (author)

Anisotropic permeable porous facing and slip velocity on squeeze film in an axially undefined journal bearing with ferrofluid lubricant

International Nuclear Information System (INIS)

Shah, R.C.; Bhat, M.V.

2004-01-01

Ferrofluid squeeze film in an axially undefined porous journal bearing was analyzed to determine its performance considering anisotropic permeability of the porous facing and slip velocity at the interface of porous matrix and film region using Jenkins flow model. Expressions were obtained for dimensionless pressure, load capacity and response time of the squeeze film. How to deduce results for no-slip case, isotropic porous case and for Neuringer-Rosensweig model case were indicated. The computed values of dimensionless load capacity and response time were displayed in graphical form. They increased with increasing values of eccentricity ratio and anisotropic parameter while they decreased with increasing values of slip parameter or material parameter of Jenkins model

Magnetic-field induced semimetal in topological crystalline insulator thin films

International Nuclear Information System (INIS)

Ezawa, Motohiko

2015-01-01

We investigate electromagnetic properties of a topological crystalline insulator (TCI) thin film under external electromagnetic fields. The TCI thin film is a topological insulator indexed by the mirror-Chern number. It is demonstrated that the gap closes together with the emergence of a pair of gapless cones carrying opposite chirarities by applying in-plane magnetic field. A pair of gapless points have opposite vortex numbers. This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal. We thus present an a magnetic-field induced semimetal–semiconductor transition in 2D material. This is a giant-magnetoresistance, where resistivity is controlled by magnetic field. Perpendicular electric field is found to shift the gapless points and also renormalize the Fermi velocity in the direction of the in-plane magnetic field. - Highlights: • The band structure of topological crystalline insulator thin films can be controlled by applying in-plane magnetic field. • At the gap closing magnetic field, a pair of gapless cones carrying opposite chirarities emerge. • A pair of gapless points have opposite vortex numbers. • This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal. • A magnetic-field induced semimetal–semiconductor transition occurs in 2D material

Magnetic-field induced semimetal in topological crystalline insulator thin films

Energy Technology Data Exchange (ETDEWEB)

Ezawa, Motohiko, E-mail: ezawa@ap.t.u-tokyo.ac.jp

2015-06-19

We investigate electromagnetic properties of a topological crystalline insulator (TCI) thin film under external electromagnetic fields. The TCI thin film is a topological insulator indexed by the mirror-Chern number. It is demonstrated that the gap closes together with the emergence of a pair of gapless cones carrying opposite chirarities by applying in-plane magnetic field. A pair of gapless points have opposite vortex numbers. This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal. We thus present an a magnetic-field induced semimetal–semiconductor transition in 2D material. This is a giant-magnetoresistance, where resistivity is controlled by magnetic field. Perpendicular electric field is found to shift the gapless points and also renormalize the Fermi velocity in the direction of the in-plane magnetic field. - Highlights: • The band structure of topological crystalline insulator thin films can be controlled by applying in-plane magnetic field. • At the gap closing magnetic field, a pair of gapless cones carrying opposite chirarities emerge. • A pair of gapless points have opposite vortex numbers. • This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal. • A magnetic-field induced semimetal–semiconductor transition occurs in 2D material.

Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

Energy Technology Data Exchange (ETDEWEB)

Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Anupam, E-mail: anupam@austin.utexas.edu; Dey, Rik, E-mail: rikdey@utexas.edu; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C.P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

2017-09-01

Highlights: • Perpendicular magnetic anisotropy in epitaxial Cr{sub 2}Te{sub 3} has been investigated. • Presence of a relatively strong second order anisotropy contribution is observed. • Magnetization reversal is explained quantitatively using a 1D defect model. • Relative roles of nucleation and pinning in magnetization reversal are discussed. • Domain structures and switching process are visualized by micromagnetic simulation. - Abstract: We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

Surface Treatment of Polypropylene Films Using Dielectric Barrier Discharge with Magnetic Field

International Nuclear Information System (INIS)

Wang Changquan; Zhang Guixin; Wang Xinxin; Chen Zhiyu

2012-01-01

Atmospheric pressure non-thermal plasma is of interest for industrial applications. In this study, polypropylene (PP) films are modified by a dielectric barrier discharge (DBD) with a non-uniform magnetic field in air at atmospheric pressure. The surface properties of the PP films before and after a DBD treatment are studied by using contact angle measurement, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of treatment time on the surface modification with and without a magnetic field is investigated. It is found that the hydrophilic improvement depends on the treatment time and magnetic field. It is also found that surface roughness and oxygen-containing groups are introduced onto the PP film surface after the DBD treatment. Surface roughness and oxygen-containing polar functional groups of the PP films increase with the magnetic induction density. The functional groups are identified as C-O, C=O and O-C=O by using XPS analysis. It is concluded that the hydrophilic improvement of PP films treated with a magnetic field is due to a greater surface roughness and more oxygen-containing groups. (plasma technology)

Improved high-frequency soft magnetic properties of FeCo films on organic ferroelectric PVDF substrate

Energy Technology Data Exchange (ETDEWEB)

Li, Dong; Wang, Zhen; Han, Xuemeng; Li, Yue; Guo, Xiaobin; Zuo, Yalu; Xi, Li, E-mail: xili@lzu.edu.cn

2015-02-01

FeCo films with various thicknesses were fabricated by direct-current magnetron sputtering on corning glass and organic ferroelectric PVDF substrates at the same time with 5 nm Ru seed layer and 5 nm Ta protective layer. The in-plane uniaxial anisotropy field of FeCo on glass substrate increases from 24 to 36 Oe with the increase of FeCo film thickness from 5 to 100 nm. However, a large in-plane anisotropy field of FeCo on PVDF substrate increases with FeCo thickness from 5 to 20 nm and gradually decreases with the FeCo thickness further increasing. Atomic force microscope images of FeCo on glass show quite smooth surface with root-mean-square roughness around 0.5 nm and have none visible granules on the surface for all samples. While, AFM images of FeCo on PVDF show quite rough surface with RMS roughness around 25 nm and have visible granules with the smallest granules appearing at the FeCo thickness of 20 nm. The permeability spectra show the typical ferromagnetic resonance phenomenon and can be well fitted by the LLG equation with the obtained experimental parameters. The ferromagnetic resonance frequency can reach 7.0 GHz for the 20 nm FeCo film on PVDF. Moreover, the quality factor of this sample can respectively reach 26, 12 and 7 at 1.0, 2.0, and 3.0 GHz, indicating the potential real 3G application for high-frequency devices. - Highlights: 1.Magnetic and morphological properties of FeCo films on PVDF substrates are studied. 2.The large anisotropy field of FeCo films on PVDF is obtained. 3.Improved high frequency properties of FeCo films on flexible substrates are obtained. 4.The origin of improved high frequency properties of FeCo films on PVDF is studied.

Magnetic shield effect simulation of superconducting film shield covering directly coupled HTS dc-SQUID magnetometer

International Nuclear Information System (INIS)

Terauchi, N.; Noguchi, S.; Igarashi, H.

2011-01-01

A superconducting film shield over a SQUID ring improves the robustness of the SQUID with respect to magnetic noise. Supercurrent in the SQUID magnetometer and the superconducting film shield were simulated. The superconducting film shield reduces the influence of the external magnetic field on the SQUID ring. An HTS SQUID is a high sensitive magnetic sensor. In recent years, the HTS SQUID is widely used in various applications. In some applications, high robustness with respect to magnetic noise is required to realize stable operation at outside of a magnetic shielding room. The target of this paper is a directly coupled HTS dc-SQUID magnetometer. To enhance the robustness of the SQUID magnetometer, use of a superconducting thin film shield has been proposed. The magnetic field directly penetrating the SQUID ring causes the change of the critical current of Josephson junction, and then the SQUID magnetometer transitions into inoperative state. In order to confirm the magnetic shield effect of the superconducting film shield, electromagnetic field simulation with 3D edge finite element method was performed. To simulate the high temperature superconductor, E-J characteristics and c-axis anisotropy are considered. To evaluate the effect of the superconducting film shield, an external magnetic field which is supposed to be a magnetic noise is applied. From the simulation results, the time transition of the magnetic flux penetrating the SQUID ring is investigated and the effect of the superconducting film shield is confirmed. The amplitude of the magnetic flux penetrating the SQUID ring can be reduced to about one-sixth since the superconducting film shield prevents the magnetic noise from directly penetrating the SQUID ring.

Electric-field assisted switching of magnetization in perpendicularly magnetized (Ga,Mn)As films at high temperatures

Science.gov (United States)

Wang, Hailong; Ma, Jialin; Yu, Xueze; Yu, Zhifeng; Zhao, Jianhua

2017-01-01

The electric-field effects on the magnetism in perpendicularly magnetized (Ga,Mn)As films at high temperatures have been investigated. An electric-field as high as 0.6 V nm-1 is applied by utilizing a solid-state dielectric Al2O3 film as a gate insulator. The coercive field, saturation magnetization and magnetic anisotropy have been clearly changed by the gate electric-field, which are detected via the anomalous Hall effect. In terms of the Curie temperature, a variation of about 3 K is observed as determined by the temperature derivative of the sheet resistance. In addition, electrical switching of the magnetization assisted by a fixed external magnetic field at 120 K is demonstrated, employing the gate-controlled coercive field. The above experimental results have been attributed to the gate voltage modulation of the hole density in (Ga,Mn)As films, since the ferromagnetism in (Ga,Mn)As is carrier-mediated. The limited modulation magnitude of magnetism is found to result from the strong charge screening effect introduced by the high hole concentration up to 1.10  ×  1021 cm-3, while the variation of the hole density is only about 1.16  ×  1020 cm-3.

Crystallographic phases and magnetic properties of iron nitride films

Energy Technology Data Exchange (ETDEWEB)

Li, Guo-Ke [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Liu, Yan; Zhao, Rui-Bin [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Shen, Jun-Jie [Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Wang, Shang; Shan, Pu-Jia; Zhen, Cong-Mian [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Hou, Deng-Lu, E-mail: houdenglu@mail.hebtu.edu.cn [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China)

2015-08-31

Iron nitride films, including single phase films of α-FeN (expanded bcc Fe), γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N (0 ≤ x ≤ 1), and γ″-FeN, were sputtered onto AlN buffered glass substrates. It was found possible to control the phases in the films merely by changing the nitrogen partial pressure during deposition. The magnetization decreased with increased nitrogen concentration and dropped to zero when the N:Fe ratio was above 0.5. The experimental results, along with spin polarized band calculations, have been used to discuss and analyze the magnetic properties of iron nitrides. It has been demonstrated that in addition to influencing the lattice constant of the various iron nitrides, the nearest N atoms have a significant influence on the exchange splitting of the Fe atoms. Due to the hybridization of Fe-3d and N-2p states, the magnetic moment of Fe atoms decreases with an increase in the number of nearest neighbor nitrogen atoms. - Highlights: • Single phase γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N, and γ″-FeN films were obtained using dc sputtering. • The phases in iron nitride films can be controlled by the nitrogen partial pressure. • The nearest N neighbors have a significant influence on the exchange splitting of Fe.

Crystallographic phases and magnetic properties of iron nitride films

International Nuclear Information System (INIS)

Li, Guo-Ke; Liu, Yan; Zhao, Rui-Bin; Shen, Jun-Jie; Wang, Shang; Shan, Pu-Jia; Zhen, Cong-Mian; Hou, Deng-Lu

2015-01-01

Iron nitride films, including single phase films of α-FeN (expanded bcc Fe), γ′-Fe 4 N, ε-Fe 3−x N (0 ≤ x ≤ 1), and γ″-FeN, were sputtered onto AlN buffered glass substrates. It was found possible to control the phases in the films merely by changing the nitrogen partial pressure during deposition. The magnetization decreased with increased nitrogen concentration and dropped to zero when the N:Fe ratio was above 0.5. The experimental results, along with spin polarized band calculations, have been used to discuss and analyze the magnetic properties of iron nitrides. It has been demonstrated that in addition to influencing the lattice constant of the various iron nitrides, the nearest N atoms have a significant influence on the exchange splitting of the Fe atoms. Due to the hybridization of Fe-3d and N-2p states, the magnetic moment of Fe atoms decreases with an increase in the number of nearest neighbor nitrogen atoms. - Highlights: • Single phase γ′-Fe 4 N, ε-Fe 3−x N, and γ″-FeN films were obtained using dc sputtering. • The phases in iron nitride films can be controlled by the nitrogen partial pressure. • The nearest N neighbors have a significant influence on the exchange splitting of Fe

Effects of a magnetic field on growth of porous alumina films on aluminum

Energy Technology Data Exchange (ETDEWEB)

Ispas, Adriana; Bund, Andreas [Technische Universitaet Dresden, Physikalische Chemie und Elektrochemie, 01062 Dresden (Germany); Vrublevsky, Igor, E-mail: vrublevsky@bsuir.edu.b [Belarusian State University of Informatics and Radioelectronics Minsk, Department of Micro and Nanoelectronics, 220013 Minsk (Belarus)

2010-05-01

The effects induced by a magnetic field on the oxide film growth on aluminum in sulfuric, oxalic, phosphoric and sulfamic acid, and on current transients during re-anodizing of porous alumina films in the barrier-type electrolyte, were studied. Aluminum films of 100 nm thickness were prepared by thermal evaporation on Si wafer substrates. We could show that the duration of the anodizing process increased by 33% during anodizing in sulfuric acid when a magnetic field was applied (0.7 T), compared to the process without a magnetic field. Interestingly, such a magnetic field effect was not found during anodizing in oxalic and sulfamic acid. The pore intervals were decreased by ca. 17% in oxalic acid. These findings were attributed to variations in electronic properties of the anodic oxide films formed in various electrolytes and interpreted on the basis of the influence of trapped electrons on the mobility of ions migrating during the film growth. The spin dependent tunneling of electrons into the surface layer of the oxide under the magnetic field could be responsible for the shifts of the current transients to lower potentials during re-anodizing of heat-treated oxalic and phosphoric acid alumina films.

Structural and magnetic characterization of martensitic Ni-Mn-Ga thin films deposited on Mo foil

International Nuclear Information System (INIS)

Chernenko, V.A.; Anton, R. Lopez; Kohl, M.; Barandiaran, J.M.; Ohtsuka, M.; Orue, I.; Besseghini, S.

2006-01-01

Three martensitic Ni 51.4 Mn 28.3 Ga 20.3 thin films sputter-deposited on a Mo foil were investigated with regard to their crystal and magnetic domain structures, as well as their magnetic and magnetostrain properties. The film thicknesses, d, were 0.1, 0.4 and 1.0μm. X-ray and electron diffraction patterns revealed a tetragonal modulated martensitic phase (10M) in the films. The surface topography and micromagnetic structure were studied by scanning probe microscopy. A maze magnetic domain structure featuring a large out-of-plane magnetization component was found in all films. The domain width, δ, depends on the film thickness as δ∼d. The thickness dependencies of the saturation magnetization, saturation magnetic field and magnetic anisotropy were clarified. Beam cantilever tests on the Ni-Mn-Ga/Mo composite as a function of magnetic field showed reversible strains, which are larger than ordinary magnetostriction

Frequency characterization of thin soft magnetic material layers used in spiral inductors

International Nuclear Information System (INIS)

Kriga, Adoum; Allassem, Désiré; Soultan, Malloum; Chatelon, Jean-Pierre; Siblini, Ali; Allard, Bruno; Rousseau, Jean Jacques

2012-01-01

The paper details the characterization of thin magnetic materials layers, particularly soft materials, with respect to their behaviour in frequency (from 10 MHz to 1 GHz). The proposed method is suitable for any soft but insulating magnetic material; Yttrium Iron Garnet (YIG) is used as an example. The principle is based on a comparison between simulations for different values of the permeability and measurement values versus frequency of planar inductor structures; an experimental validation is proposed as well. Thin magnetic material is first deposited on an alumina substrate using RF sputtering technique; a planar spiral winding of copper is then deposited on the magnetic material by the same technique. The effective permeability versus frequency is obtained by comparing two samples of spiral windings with and without magnetic material. Network analyser measurements on samples of various geometrical dimensions and of different thicknesses are necessary to determine the effective magnetic permeability; we have obtained a relative effective permeability of about 30 for seven turns spiral inductor of a 17 μm YIG film. - Highlights: ► A simple and original method is presented for the characterization of soft magnetic layer. ► This is a non-destructive method based on standard equipment. ► The principle is based on a comparison between simulations and measurement. ► An experimental validation is proposed as well.

Temperature dependent magnetic coupling between ferromagnetic FeTaC layers in multilayer thin films

Energy Technology Data Exchange (ETDEWEB)

Singh, Akhilesh Kumar [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039 (India); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Hsu, Jen-Hwa [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Perumal, Alagarsamy, E-mail: perumal@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039 (India)

2016-11-15

We report systematic investigations on temperature dependent magnetic coupling between ferromagnetic FeTaC layers and resulting magnetic properties of multilayer structured [FeTaC (~67 nm)/Ta(x nm)]{sub 2}/FeTaC(~67 nm)] thin films, which are fabricated directly on thermally oxidized Si substrate. As-deposited amorphous films are post annealed at different annealing temperatures (T{sub A}=200, 300 and 400 °C). Structural analyzes reveal that the films annealed at T{sub A}≤200 °C exhibit amorphous nature, while the films annealed above 200 °C show nucleation of nanocrystals at T{sub A}=300 °C and well-defined α-Fe nanocrystals with size of about 9 nm in amorphous matrix for 400 °C annealed films. Room temperature and temperature dependent magnetic hysteresis (M–H) loops reveal that magnetization reversal behaviors and magnetic properties are strongly depending on spacer layer thickness (x), T{sub A} and temperature. A large reduction in coercivity (H{sub C}) was observed for the films annealed at 200 °C and correlated to relaxation of stress quenched in during the film deposition. On the other hand, the films annealed at 300 °C exhibit unusual variation of H{sub C}(T), i.e., a broad minimum in H{sub C}(T) vs T curve. This is caused by change in magnetic coupling between ferromagnetic layers having different microstructure. In addition, the broad minimum in the H{sub C}(T) curve shifts from 150 K for x=1 film to 80 K for x=4 film. High-temperature thermomagnetization data show a strong (significant) variation of Curie temperature (T{sub C}) with T{sub A} (x). The multilayer films annealed at 200 °C exhibit low value of T{sub C} with a minimum of 350 K for x=4 film. But, the films annealed at 400 °C show largest T{sub C} with a maximum of 869 K for x=1 film. The observed results are discussed on the basis of variations in magnetic couplings between FeTaC layers, which are majorly driven by temperature, spacer layer thickness, annealing temperature and

Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

International Nuclear Information System (INIS)

Ngo, Duc-The; Tran, Quang-Hung; Møhave, Kristian; Quach, Duy-Truong; Phan, The-Long; Kim, Dong-Hyun

2014-01-01

The perpendicular magnetic anisotropy (PMA) and dynamic magnetization-reversal process in [CoFeB t nm/Pd 1.0 nm] n (t = 0.4, 0.6, 0.8, 1.0 and 1.2 nm; n = 2 − 20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an effective uniaxial anisotropy up to 7.7 × 10 6  Jm −3 and a saturation magnetization as low as 200 emu cm −3 are achieved. The surface/interfacial anisotropy of the CoFeB/Pd interfaces—the main contribution to the PMA—is separated from the effective uniaxial anisotropy of the films and appears to increase with the number of CoFeB/Pd bilayers. Observation of the magnetic domains during a magnetization-reversal process, using polar magneto-optical Kerr microscopy, reveals the detailed behavior of the nucleation and displacement of the domain walls. (paper)

Magnetic properties of ultrathin Co/Ge(111) and Co/Ge(100) films

International Nuclear Information System (INIS)

Cheng, W. C.; Tsay, J. S.; Yao, Y. D.; Lin, K. C.; Yang, C. S.; Lee, S. F.; Tseng, T. K.; Neih, H. Y.

2001-01-01

The orientation of the magnetization and the occurrence of interfacial ferromagnetic inactive layers for ultrathin Co films grown on Ge(111) and Ge(100) surfaces have been studied using the in situ surface magneto-optic Kerr effect. On a Ge(111) substrate, cobalt films (≤28 monolayers) with in-plane easy axis of magnetization have been observed; however, on a Ge(100) substrate, ultrathin Co films (14 - 16 monolayers) with canted out-of-plane easy axis of magnetization were measured. The ferromagnetic inactive layers were formed due to the intermixing of Co and Ge and lowering the Curie temperature by reducing Co film thickness. The Co - Ge compound inactive layers were 3.8 monolayers thick for Co films grown on Ge(111) and 6.2 monolayers thick for Co films deposited on Ge(100). This is attributed to the difference of the density of surface atoms on Ge(111) and Ge(100). [copyright] 2001 American Institute of Physics

Strain dependent magnetic properties of LSMO films prepared by pulsed laser deposition

International Nuclear Information System (INIS)

Prajapat, C.L.; Gupta, N.; Singh, M.R.; Mishra, P.K.; Gupta, S.K.; Ravikumar, G.; Bhattacharya, D.; Singh, Surendra; Basu, S.; Roul, B.K.

2014-01-01

Perovskite manganites exhibiting colossal magnetoresistance (CMR) are ideal candidates for growth of epitaxial multilayers with oxide high temperature superconductors owing to their structural similarity and comparable growth conditions. They are widely employed in studies on superconductor/ferromagnet-superlattices. Among the manganites, La 2/3 Sr 1/3 MnO 3 (LSMO) has one of the highest FM transition temperatures (above 300K). Magnetic properties of films that are dependent on strain (such as coercivity) can be tuned by varying deposition conditions, by using different substrates and varying thickness of films in nano range. Lattice mismatch between LSMO with STO and MgO substrates are 0.6% and 8% respectively. This mismatch produces tensile strain in LSMO films and changes its magnetic properties. We study the change in magnetic properties of epitaxial LSMO thin films on MgO (100) and STO (100) substrates with varying thickness to change the strain in the film. LSMO films are prepared by pulsed laser deposition

Magnetic resonance study of bulk and thin film EuTiO3

International Nuclear Information System (INIS)

Laguta, V V; Kamba, S; Maryško, M; Andrzejewski, B; Kachlík, M; Maca, K; Lee, J H; Schlom, D G

2017-01-01

Magnetic resonance spectra of EuTiO 3 in both bulk and thin film form were taken at temperatures from 3–350 K and microwave frequencies from 9.2–9.8 and 34 GHz. In the paramagnetic phase, magnetic resonance spectra are determined by magnetic dipole and exchange interactions between Eu 2+ spins. In the film, a large contribution arises from the demagnetization field. From detailed analysis of the linewidth and its temperature dependence, the parameters of spin–spin interactions were determined: the exchange frequency is 10.5 GHz and the estimated critical exponent of the spin correlation length is  ≈0.4. In the bulk samples, the spectra exhibited a distinct minimum in the linewidth at the Néel temperature, T N   ≈  5.5 K, while the resonance field practically does not change even on cooling below T N . This is indicative of a small magnetic anisotropy ∼320 G in the antiferromagnetic phase. In the film, the magnetic resonance spectrum is split below T N into several components due to excitation of the magnetostatic modes, corresponding to a non-uniform precession of magnetization. Moreover, the film was observed to degrade over two years. This was manifested by an increase of defects and a change in the domain structure. The saturated magnetization in the film, estimated from the magnetic resonance spectrum, was about 900 emu cm −3 or 5.5 µ B /unit cell at T   =  3.5 K. (paper)

Structural and magnetic properties of SmCo-based magnetic films grown by electron-beam evaporation

Energy Technology Data Exchange (ETDEWEB)

Saravanan, P., E-mail: psdrdo@gmail.com [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Vinod, V.T.P.; Černík, Miroslav [Institute for Nanomaterials, Advanced Technologies and Innovation, Department of Natural Sciences, Technical University of Liberec, Studentská 1402/2, Liberec 1, 461 17 (Czech Republic); Vishnuraj, R.; Arout Chelvane, J.; Kamat, S.V. [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Hsu, Jen-Hwa, E-mail: jhhsu@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

2015-07-01

Sub-micron thick Sm–Co films (200 and 300 nm) with selective phase composition are grown on Si (100) substrates by electron-beam evaporation using Sm-lean alloy targets such as Sm{sub 4}Co{sub 96} and Sm{sub 8}Co{sub 92}. The structural and magnetic properties of Sm–Co films are characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and super-conducting quantum interference device (SQUID) magnetometer. The Sm–Co films obtained with the Sm{sub 4}Co{sub 96} target exhibit Sm{sub 2}Co{sub 17} as a prominent phase; while the films produced with the Sm{sub 8}Co{sub 92} target show Sm{sub 2}Co{sub 7} as a major phase. Both the Sm–Co films reveal granular morphology; however, the estimated grain size values are slightly lower in the case of Sm{sub 2}Co{sub 7} films, irrespective of their thicknesses. Coercivity (H{sub c}) values of 1.48 and 0.9 kOe are achieved for the as-grown 200-nm thick Sm{sub 2}Co{sub 17} and Sm{sub 2}Co{sub 7}-films. Temperature-dependent magnetization studies confirm that the demagnetization behaviors of these films are consistent with respect to the identified phase composition. Upon rapid thermal annealing, maximum H{sub c} value of 8.4 kOe is achieved for the 200 nm thick Sm{sub 2}Co{sub 17}-films. As far as e-beam evaporated Sm–Co films are concerned, this H{sub c} value is one of the best values reported so far. - Highlights: • Electron-beam evaporation was exploited to grow sub-μm thick Sm–Co films. • Sm{sub 2}Co{sub 7} and Sm{sub 2}Co{sub 17} magnetic phases were crystallized using Sm-lean alloy targets. • Both 200 and 300-nm thick Sm–Co films revealed distinct granular morphology. • Sm–Co films of lower thickness exhibited high H{sub c} and low M{sub s} and vice-versa. • Coercivity value of 8.4 kOe achieved for the 200-nm thick Sm{sub 2}Co{sub 17}-films after RTA.

Defect-mediated magnetism of transition metal doped zinc oxide thin films

Science.gov (United States)

Roberts, Bradley Kirk

Magnetism in transition metal doped wide band-gap materials is of interest to further the fundamental science of materials and future spintronics applications. Large inter-dopant separations require mediation of ferromagnetism by some method; carrier-mediated mechanisms are typically applicable to dilute magnetic semiconductors with low Curie temperatures. Dilute magnetic oxides, commonly with poor conductivity and TC above room temperature, cannot be described within this theory. Recent experiment and theory developments suggest that ferromagnetic exchange in these materials can be mediated by defects. This research includes experimental results justifying and developing this approach. Thin films of Cr doped ZnO (band gap ˜3.3 eV) were deposited with several processing variations to enhance the effects of either 0-dimensional (vacancy, hydrogen-related defect) or two-dimensional defects (surface/interface) and thereby affect magnetism and conductivity. We observe surface magnetism in dielectric thin films of oxygen-saturated ZnO:Cr with spontaneous magnetic moment and conductance dropping approximately exponentially with increasing thickness. Uniform defect concentrations would not result in such magnetic ordering behavior indicating that magnetism is mediated either by surface defects or differing concentrations of point defects near the surface. Polarized neutron reflectivity profiling confirms a magnetically active region of ˜8 nm at the film surface. Hydrogen is notoriously present as a defect and carrier dopant in ZnO, and artificial introduction of hydrogen in dielectric ZnO:Cr films results in varying electronic and magnetic behavior. Free carriers introduced with hydrogen doping are not spin-polarized requiring an alternative explanation for ferromagnetism. We find from positron annihilation spectroscopy measurements that hydrogen doping increases the concentration of an altered VZn-related defect (a preliminary interpretation) throughout the film, which

Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

DEFF Research Database (Denmark)

Ngo, Duc-The; Quach, Duy-Truong; Hung, Tran Quang

2014-01-01

The perpendicular magnetic anisotropy (PMA) and dynamic magnetization-reversal process in [CoFeB t nm/Pd 1.0 nm]n(t = 0.4, 0.6, 0.8, 1.0 and 1.2 nm; n = 2 − 20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an eff...

Optimization of film synthesized rare earth transition metal permanent magnet systems

International Nuclear Information System (INIS)

Cadieu, F.J.

1990-01-01

This report reviews work on the optimization of film synthesized rare earth transition metal permanent magnet systems. Topics include: high coercivity in Sm-Fe-Ti-V, Sm-Fe-V, and two element systems; ThMn 12 type pseudobinary SmFe 12 - X T X ; and sputter process control for the synthesis of precisely textured RE-TM magnetic films. (JL)

Control of magnetism in dilute magnetic semiconductor (Ga,Mn)As films by surface decoration of molecules

Science.gov (United States)

Wang, Hailong; Wang, Xiaolei; Xiong, Peng; Zhao, Jianhua

2016-03-01

The responses of magnetic moments to external stimuli such as magnetic-field, heat, light and electric-field have been utilized to manipulate the magnetism in magnetic semiconductors, with many of the novel ideas applied even to ferromagnetic metals. Here, we review a new experimental development on the control of magnetism in (Ga,Mn)As thin films by surface decoration of organic molecules: Molecules deposited on the surface of (Ga,Mn)As thin films are shown to be capable of significantly modulating their saturation magnetization and Curie temperature. These phenomena are shown to originate from the carrier-mediated ferromagnetism in (Ga,Mn)As and the surface molecules acting as acceptors or donors depending on their highest occupied molecular orbitals, resembling the charge transfer mechanism in a pn junction in which the equilibrium state is reached on the alignment of Fermi levels.

Control of magnetism in dilute magnetic semiconductor (Ga,MnAs films by surface decoration of molecules

Directory of Open Access Journals (Sweden)

Hailong eWang

2016-03-01

Full Text Available The responses of magnetic moments to external stimuli such as magnetic-field, heat, light and electric-field have been utilized to manipulate the magnetism in magnetic semiconductors, with many of the novel ideas applied even to ferromagnetic metals. Here, we review a new experimental development on the control of magnetism in (Ga,MnAs thin films by surface decoration of organic molecules: Molecules deposited on the surface of (Ga,MnAs thin films are shown to be capable of significantly modulating their saturation magnetization and Curie temperature. These phenomena are shown to originate from the carrier-mediated ferromagnetism in (Ga,MnAs and the surface molecules acting as acceptors or donors depending on their highest occupied molecular orbitals, resembling the charge transfer mechanism in a pn junction in which the equilibrium state is reached on the alignment of Fermi levels.

Controlling the induced anisotropy in soft magnetic films for high-frequency applications

NARCIS (Netherlands)

Chezan, A.R.; Craus, C.B.; Chechenin, N.G.; Vystavel, T.; Hosson, J.Th.M. De; Niesen, L.; Boerma, D.O.

Nanocrystalline soft magnetic Fe–Zr–N films were successfully deposited by dc magnetron reactive sputtering. The nitrogen content was controlled by varying the Ar/N2 ratio and/or the substrate temperature. The films have saturation magnetization and induced uniaxial anisotropy values in the range

Magnetoelectric properties of magnetic/ferroelectric multilayer thin films

Energy Technology Data Exchange (ETDEWEB)

Hwang, Sung-Ok; Eum, You-Jeong; Koo, Chang-Young; Lee, Hee-Young [Yeungnam University, Gyeongsan (Korea, Republic of); Park, Jung-Min [Osaka University, Osaka (Japan); Ryu, Jung-Ho [Korea Institute of Materials Science, Changwon (Korea, Republic of)

2014-07-15

Magnetic/ferroelectric multilayer thin films using PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} (PZT) and two different magnetic materials, i.e., Terfenol-D and CuFe{sub 2}O{sub 4} (CuFO) layers, were fabricated, and their magnetoelectric (ME) coupling behavior was investigated. The PZT layer was first coated onto Pt/Ti/SiO{sub 2}/Si substrate by sol-gel spin coating method. Pt layer, which served as an electrode and a diffusion barrier, was grown on the PZT layer by using the ion-beam sputtering method. The ME voltage coefficients were calculated from the ME voltage data measured utilizing a magnetoelectric test system. The Terfenol-D/Pt/PZT films were found to show a higher in-plane ME voltage coefficient than that the CuFO/Pt/PZT films due primarily to the higher magnetostriction coefficient of Terfenol-D.

Soft magnetic properties and damping parameter of (FeCo-Al alloy thin films

Directory of Open Access Journals (Sweden)

Isao Kanada

2017-05-01

Full Text Available For high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo-Al alloy thin films has been carried out. A low effective damping parameter αeff of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2∼0.3 for (Fe1-yCoy98Al2 alloy thin films deposited onto fused silica and MgO(100 at an ambient temperature during deposition. Those films are of the bcc structure with the orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications.

Piezoelectric response of a PZT thin film to magnetic fields from permanent magnet and coil combination

Energy Technology Data Exchange (ETDEWEB)

Guiffard, B.; Seveno, R. [Universite de Nantes, Lunam Universite, IETR UMR CNRS 6164, Nantes (France)

2014-07-10

In this study, we report the magnetically induced electric field E{sub 3} in Pb(Zr{sub 0.57}Ti{sub 0.43})O{sub 3} (PZT) thin films, when they are subjected to both dynamic magnetic induction (magnitude B{sub ac} at 45 kHz) and static magnetic induction (B{sub dc}) generated by a coil and a single permanent magnet, respectively. It is found that highest sensitivity to B{sub dc} - Δ vertical stroke E{sub 3} vertical stroke ΔB{sub dc} - is achieved for the thin film with largest effective electrode. This magnetoelectric (ME) effect is interpreted in terms of coupling between eddy current-induced Lorentz forces (stress) in the electrodes of PZT and piezoelectricity. Such coupling was evidenced by convenient modelling of experimental variations of electric field magnitude with both B{sub ac} and B{sub dc} induction magnitudes, providing imperfect open circuit condition was considered. Phase angle of E{sub 3} versus B{sub dc} could also be modelled. At last, the results show that similar to multilayered piezoelectric-magnetostrictive composite film, a PZT thin film made with a simple manufacturing process can behave as a static or dynamic magnetic field sensor. In this latter case, a large ME voltage coefficient of α = vertical stroke E{sub 3} vertical stroke /B{sub ac} = 3.55 V/cm Oe under B{sub dc} = 0.3 T was found. All these results may provide promising low-cost magnetic energy harvesting applications with microsized systems. (orig.)

Enhanced magnetostriction derived from magnetic single domain structures in cluster-assembled SmCo films

Science.gov (United States)

Bai, Yulong; Yang, Bo; Guo, Fei; Lu, Qingshan; Zhao, Shifeng

2017-11-01

Cluster-assembled SmCo alloy films were prepared by low energy cluster beam deposition. The structure, magnetic domain, magnetization, and magnetostriction of the films were characterized. It is shown that the as-prepared films are assembled in compact and uniformly distributed spherical cluster nanoparticles, most of which, after vacuum in situ annealing at 700 K, aggregated to form cluster islands. These cluster islands result in transformations from superparamagnetic states to magnetic single domain (MSD) states in the films. Such MSD structures contribute to the enhanced magnetostrictive behaviors with a saturation magnetostrictive coefficient of 160 × 10-6 in comparison to 105 × 10-6 for the as-prepared films. This work demonstrates candidate materials that could be applied in nano-electro-mechanical systems, low power information storage, and weak magnetic detecting devices.

High resolution method for the magnetic axis localization for multipole magnets on the base of the garnet films technology

International Nuclear Information System (INIS)

Gertsev, K.F.; Gribkov, V.L.; Liskov, V.A.; Chervonenkis, A.J.

1992-01-01

The methods of stretched wires for the localization of the magnetic axis may be inconvenient sometimes in accelerators and colliders of very high energies because of high gradients, large lengths and small apertures. High gradients may deform the wires due to the nonzero magnetic susceptibility and microscopic ferromagnetic particles on their surface. Long wires have large sagittas and small apertures of magnets limit the transversal working domains for the measuring devices. Precision optics magnets possess extreme parameters, in particular, in interaction regions. The magneto-optic (MO) methods of the measurements present some new possibilities for the solution of the above problems. The use of MO films for magnetic field visualization and mapping was proposed and shown that on the basis of Bi-substituted iron garnet films and MO Faraday effect it's possible to obtain the quantitative vector maps of complicated magnetic field structure. Later this was described on a large scale. This method was discussed in terms of its applicability to the magnetic axis localization in quadrupoles of accelerators. In our opinion, the films technology has great advantages as compared with the colloidal solution. In this paper the principles and variants of the films method are presented and further development of the method under discussion is described

Magnetic properties of amorphous Tb-Fe thin films with an artificially layered structure

International Nuclear Information System (INIS)

Sato, N.

1986-01-01

An alternating terbium-iron (Tb-Fe) multilayer structure artificially made in amorphous Tb-Fe thin films gives rise to excellent magnetic properties of large perpendicular uniaxial anisotropy, large saturation magnetization, and large coercivity over a wide range of Tb composition in the films. The films are superior to amorphous Tb-Fe alloy thin films, especially when they are piled up with a monatomic layer of Tb and several atomic layers of Fe in an alternating fashion. Small-angle x-ray diffraction analysis confirmed the layering of monatomic layers of Tb and Fe, where the periodicity of the layers was found to be about 5.9 A. Direct evidence for an artificially layered structure was obtained by transmission electron microscopic and Auger electron spectroscopic observations. Together with magnetic measurements of hysteresis loops and torque curves, it has been concluded that the most important origin of the large magnetic uniaxial anisotropy can be attributed to the Tb-Fe pairs aligned perpendicular to the films

High magnetic field quantum transport in Au nanoparticle–cellulose films

International Nuclear Information System (INIS)

Turyanska, L; Makarovsky, O; Patanè, A; Kozlova, N V; Liu, Z; Li, M; Mann, S

2012-01-01

We report the magneto-transport properties of cellulose films comprising interconnected networks of gold nanoparticles (Au NPs). Cellulose is a biopolymer that can be made electrically conducting by cellulose regeneration in Au NP dispersions. The mechanism of electronic conduction in the Au–cellulose films changes from variable range hopping to metallic-like conduction with decreasing resistivity. Our experiments in high magnetic fields (up to 45 T) reveal negative magnetoresistance in the highly resistive films. This is attributed to the spin polarization of the Au NPs and the magnetic field induced suppression of electron spin flips during spin-polarized tunneling in the NP network. (paper)

Perpendicular magnetic anisotropy in Mn2VIn (001) films: An ab initio study

Science.gov (United States)

Zipporah, Muthui; Robinson, Musembi; Julius, Mwabora; Arti, Kashyap

2018-05-01

First principles study of the magnetic anisotropy of Mn2VIn (001) films show perpendicular magnetic anisotropy (PMA), which increases as a function of the thickness of the film. Density functional theory (DFT) as implemented in the Vienna Ab initio simulation package (VASP) is employed here to perform a comprehensive theoretical investigation of the structural, electronic and magnetic properties of the Mn2VIn(001) films of varying thickness. Our calculations were performed on fully relaxed structures, with five to seventeen mono layers (ML). The degree of spin polarization is higher in the (001) Mn2VIn thin films as compared to the bulk in contrast to what is usually the case and as in Mn2VAl, which is isoelectronic to Mn2VIn as well as inCo2VIn (001) films studied for comparison. Tetragonal distortions are found in all the systems after relaxation. The distortion in the Mn2VIn system persists even for the 17ML thin film, resulting in PMA in the Mn2VIn system. This significant finding has potential to contribute to spin transfer torque (STT) and magnetic random access memory MRAM applications, as materials with PMA derived from volume magnetocrystalline anisotropy are being proposed as ideal magnetic electrodes.

Object representation and magnetic moments in thin alkali films

Science.gov (United States)

Garrett, Douglas C.

2008-10-01

This thesis is broken into two parts a computer vision part and a solid state physics part. In the computer vision part of the thesis (chapters 1 through 5), the concept of an architecture is discussed with a review of what is known about the brain's visual architecture as it applies to object representation. With this in mind we review the two main types of architectures that are used in computer vision for object representation. A specific object representation is then implemented and optimized to solve a problem in object tracking. This representation is then used to derive the fiducial points of a face using two distinct methods. One using evolutionary algorithms and another by a Bayesian analysis of the feature responses drawn from a gallery of faces. The evolved fiducial representation is tested as a facial detection system. It is shown that the Bayesian analysis of facial images gives an entropy measure that can be used to further improve detection results in the facial detection system. In addition, two similarity metrics are explored in the context of facial detection. It is found that a normalized vector dot product substantially outperforms the Euclidean distance measure. The solid state part of the thesis is composed of two self contained chapters. An effort has been made to reduce the redundancies between the material but some will necessarily remain (i.e., short descriptions of the experimental setup). Both chapters deal with the phenomenon of magnetism of atomic impurities in and on thin metal host films. The important difference between the chapters, besides the results, lies in the experimental technique used to measure the magnetism. In chapter 6, thin films of Pb are covered in situ with sub monolayers of V, Mo and Co in the range between 0.01 and 1 monolayers. If the surface impurities are magnetic they will reduce the superconducting transition temperature of the Pb film. From the reduction of Tc the magnetic dephasing rate of the surface

Growth and magnetic structure of La0.67Sr0.33MnO3 films

International Nuclear Information System (INIS)

Brown, G.W.; Jia, Q.X.; Peterson, E.J.; Hristova, D.K.; Hundley, M.F.; Thompson, J.D.; Maggiore, C.J.; Tesmer, J.; Hawley, M.E.

1997-01-01

Growth of LaMnO 3 films that exhibit colossal magnetoresistance (CMR) has concentrated heavily on Ca doped materials. However, since the 33% Sr doped films are ferromagnetic at room temperature, they are ideal candidates for dual growth-magnetic structure studies using scanned probe techniques. In this study, interest was focused on the relations between growth/processing parameters, film morphology, and electronic/magnetic properties. In addition, films were grown on both LaAlO 3 (LAO) and SrTiO 3 (STO) to examine the results of stress induced by different substrate mismatches. La 0.67 Sr 0.33 MnO 3 (LSMO) was grown using pulsed laser deposition (PLD) at temperatures between 500 C and 800 C. The film microstructure, crystallinity, and magnetic and electrical properties were characterized by room temperature scanning tunneling microscopy (STM), atomic force microscopy (AFM), magnetic force microscopy (MFM), x-ray diffraction, and temperature dependent transport and magnetization measurements. The growth trends follow those previously reported for Ca doped films. Grains increase in size with increasing temperature and coalesce into extended layers after annealing. Although topographic contributions complicate interpretation of some MFM data, local magnetic structure observed here is generally associated with film defects

Hyperfine interaction studies and magnetic properties of FeCoAlN nanocomposite films

International Nuclear Information System (INIS)

Lancok, A.; Zaveta, K.; Kanuch, T.; Miglierini, M.; Lancok, J.; Postava, K.; Kohout, J.; Zivotsky, O.; Fendrych, F.

2008-01-01

Nanogranular magnetic films were produced by specially designed UHV plasma-jet system with DC hollow-cathode discharge. We investigated the properties of these ferromagnetic FeCoAlN-based films. The analyses of the samples were additionally complemented by the study of nuclear magnetic resonance (NMR), Moessbauer spectroscopy, magnetic measurements, and X-ray diffraction.

Study of mechanical-magnetic and electromagnetic properties of PZT/Ni film systems by a novel bulge technique

Energy Technology Data Exchange (ETDEWEB)

Liu, Q.; Zhou, W.; Ding, J.; Xiao, M. [School of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Key Laboratory of Film Materials and Devices of Science and Technology Department of Hunan Province, Xiangtan University, Hunan 411105 (China); Yu, Z.J.; Xu, H. [State Key Lab for Turbulence and Complex Systems, Peking University, Beijing 100871 (China); Mao, W.G., E-mail: ssamao@126.com [School of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Key Laboratory of Film Materials and Devices of Science and Technology Department of Hunan Province, Xiangtan University, Hunan 411105 (China); Pei, Y.M.; Li, F.X. [State Key Lab for Turbulence and Complex Systems, Peking University, Beijing 100871 (China); Feng, X. [AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Fang, D.N., E-mail: fangdn@pku.edu.cn [State Key Lab for Turbulence and Complex Systems, Peking University, Beijing 100871 (China); Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081 (China)

2017-02-01

A novel multiple functional bulge apparatus was designed to study the mechanical-electronic-magnetic characteristics of electromagnetic materials. The elastic modulus difference effect of Ni thin film was observed and it was about 22.16% in the demagnetized and magnetization saturated states. The mechanical-magnetic behaviors of Ni and lead-titanate zirconate (PZT)/Ni films were in-situ measured by using the new bulge systems, respectively. The evolutions of three key material properties in hysteresis loop including saturation magnetization, remanent magnetization and coercive field were discussed in detail, respectively. The mechanisms of mechanical-magnetic coupled behaviors of Ni and PZT/Ni films were analyzed with the aid of the competitive relationship of stress and magnetization. Similarly, the electronic-magnetic characteristics of PZT/Ni films were in-situ measured by using this experimental system. The evolution of saturated magnetization, remanent magnetization and coercive field Kerr signals were discussed with the magneto-elastic anisotropy energy point. In this paper, a suitable mechanical-electronic-magnetic bulge measurement system was established, which would provide a good choice for further understanding the multi field coupling characteristics of electromagnetic film materials. - Highlights: • A novel bulge apparatus was designed to study electromagnetic materials. • The mechanical-magnetic features of Ni film were studied by this new apparatus. • The ΔE effect of Ni film was observed and analyzed. • The mechanical electronic-magnetic characteristics of PZT/Ni film were discussed.

Observation and manipulation of magnetic domains in sol gel derived thin films of spinel ferrites

Science.gov (United States)

Datar, Ashwini A.; Mathe, Vikas L.

2017-12-01

Thin films of spinel ferrites, namely zinc substituted nickel, cobalt ferrite, and manganese substituted cobalt ferrite, were synthesized using sol-gel derived spin-coating techniques. The films were characterized using x-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy techniques for the analysis of structural, morphological and vibrational band transition properties, which confirm the spinel phase formation of the films. The magnetic force microscopy (MFM) technique was used to observe the magnetic domain structure present in the synthesized films. Further, the films were subjected to an external DC magnetic field of 2 kG to orient the magnetic domains and analyzed using an ex situ MFM technique.

Femtosecond laser spectroscopy of spins: Magnetization dynamics in thin magnetic films with spatio-temporal resolution

International Nuclear Information System (INIS)

Carpene, E.; Mancini, E.; Dallera, C.; Puppin, E.; De Silvestri, S.

2010-01-01

Based on the Magneto-Optical Kerr Effect (MOKE), we have developed an experimental set-up that allows us to fully characterize the magnetization dynamics in thin magnetic films by measuring all three real space components of the magnetization vector M. By means of the pump-probe technique it is possible to extract the time dependence of each individual projection with sub-picosecond resolution. This method has been exploited to investigate the temporal evolution of the magnetization (modulus and orientation) induced by an ultrashort laser pulse in thin epitaxial iron films. According to our results, we deduced that the initial, sub-picosecond demagnetization is established at the electronic level through electron-magnon excitations. The subsequent dynamics is characterized by a precessional motion on the 100 ps time scale, around an effective, time-dependent magnetic field. Following the full dynamics of M, the temporal evolution of the magneto-crystalline anisotropy constant can be unambiguously determined, providing the experimental evidence that the precession is triggered by the rapid, optically-induced misalignment between the magnetization vector and the effective magnetic field. These results suggest a possible pathway toward the ultrarapid switching of the magnetization.

Magnetic force acting on a magnetic dipole over a superconducting thin film

International Nuclear Information System (INIS)

Wei, J.C.; Chen, J.L.; Horng, L.; Yang, T.J.

1996-01-01

The magnetostatic interaction energy and corresponding magnetic force acting on a magnetic point dipole placed above a type-II thin superconducting film in the mixed state with a single vortex are calculated using electromagnetics coupled with the London theory of superconductivity. If a vortex is trapped by a circular defect of radius b 1, where a is the separation between the dipole and the thin film, the only difference between two results is in the cutoff length, i.e., in the case of a circular defect the only difference in the critical position calculation is the cutoff at radius b rather than at coherence length ξ. The pinning force of a single vortex by a circular defect is also calculated. Further, we investigate the conditions of the vortex creation for various cases (including the first, second, and third vortices) for a free of pinning center in the examining region. It is found that the creation of a new single vortex in the thin film causes an abrupt change in vertical levitation force: the force changed discontinuously. copyright 1996 The American Physical Society

Studying the initial stages of film electrodeposition of magnetic cobalt-tungsten alloys

International Nuclear Information System (INIS)

Rachinskas, V.S.; Orlovskaya, L.V.; Parfenov, V.A.; Yasulajtene, V.V.

1996-01-01

Initial stages of magnetic film electrodeposition by recording potentiodynamic polarization and j c ,t-curves, determination of surface structure of electrolytically deposited films by the method of XPS and study of thin coating properties have been considered. It is shown that at initial stage of electrodeposition of magnetic Co-W-films a sharp decrease in cathode process rate and formation of Co(OH) 2 , WO 3 and/or WO 4 2- occur on Cu-cathode surface. Electrodeposition of metallic magnetic Co-W-alloy, consisting of Co, W and containing basic compounds of co-deposited metals, takes place after a certain time period depending on deposition E c . 6 refs.; 3 figs

Soft magnetism, magnetostriction, and microwave properties of FeGaB thin films

International Nuclear Information System (INIS)

Lou, J.; Insignares, R. E.; Cai, Z.; Ziemer, K. S.; Liu, M.; Sun, N. X.

2007-01-01

A series of (Fe 100-y Ga y ) 1-x B x (x=0-21 and y=9-17) films were deposited; their microstructure, soft magnetism, magnetostrictive behavior, and microwave properties were investigated. The addition of B changes the FeGaB films from polycrystalline to amorphous phase and leads to excellent magnetic softness with coercivity s , self-biased ferromagnetic resonance (FMR) frequency of 1.85 GHz, narrow FMR linewidth (X band) of 16-20 Oe, and a high saturation magnetostriction constant of 70 ppm. The combination of these properties makes the FeGaB films potential candidates for tunable magnetoelectric microwave devices and other rf/microwave magnetic device applications

Ferromagnetic resonance linewidth and damping in perpendicular-anisotropy magnetic multilayers thin films

Science.gov (United States)

Beaujour, Jean-Marc

2010-03-01

Transition metal ferromagnetic films with perpendicular magnetic anisotropy (PMA) have ferromagnetic resonance (FMR) linewidths that are one order of magnitude larger than soft magnetic materials, such as pure iron (Fe) and permalloy (NiFe) thin films. We have conducted systematic studies of a variety of thin film materials with perpendicular magnetic anisotropy to investigate the origin of the enhanced FMR linewidths, including Ni/Co and CoFeB/Co/Ni multilayers. In Ni/Co multilayers the PMA was systematically reduced by irradiation with Helium ions, leading to a transition from out-of-plane to in-plane easy axis with increasing He ion fluence [1,2]. The FMR linewidth depends linearly on frequency for perpendicular applied fields and increases significantly when the magnetization is rotated into the film plane with an applied in-plane magnetic field. Irradiation of the film with Helium ions decreases the PMA and the distribution of PMA parameters, leading to a large reduction in the FMR linewidth for in-plane magnetization. These results suggest that fluctuations in the PMA lead to a large two magnon scattering contribution to the linewidth for in-plane magnetization and establish that the Gilbert damping is enhanced in such materials (α˜0.04, compared to α˜0.002 for pure Fe) [2]. We compare these results to those on CoFeB/Co/Ni and published results on other thin film materials with PMA [e.g., Ref. 3]. [1] D. Stanescu et al., J. Appl. Phys. 103, 07B529 (2008). [2] J-M. L. Beaujour, D. Ravelosona, I. Tudosa, E. Fullerton, and A. D. Kent, Phys. Rev. B RC 80, 180415 (2009). [3] N. Mo, J. Hohlfeld, M. ulIslam, C. S. Brown, E. Girt, P. Krivosik, W. Tong, A. Rebel, and C. E. Patton, Appl. Phys. Lett. 92, 022506 (2008). *Research done in collaboration with: A. D. Kent, New York University, D. Ravelosona, Institut d'Electronique Fondamentale, UMR CNRS 8622, Universit'e Paris Sud, E. E. Fullerton, Center for Magnetic Recording Research, UCSD, and supported by NSF

Room temperature deposition of perpendicular magnetic anisotropic Co{sub 3}Pt thin films on glass substrate

Energy Technology Data Exchange (ETDEWEB)

Chen, Yu-Shen; Dai, Hong-Yu; Hsu, Yi-Wei [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Ou, Sin-Liang, E-mail: slo@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Chen, Shi-Wei [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300, Taiwan (China); Lu, Hsi-Chuan; Wang, Sea-Fue [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China)

2017-03-01

Co{sub 3}Pt alloy thin films were deposited on the glass substrate at room temperature (RT) and 300 °C, which showed high perpendicular magnetic anisotropy (PMA) and isotropy magnetic behaviors, respectively. Co{sub 3}Pt HCP (0002) planes grew along the substrate plane for the films deposited at RT. The easy axis [0001] was consequently vertical to the substrate surface and obtained the predominant PMA. Large magnetic domains and sharp boundary also supported high PMA in RT-deposited samples. On the other hand, the PMA was significantly decreased with increasing the deposition temperature from RT to 300 °C. Hard HCP(0002) and soft A1(111) co-existed in the film and the magnetic exchanged coupling between these two phases induced isotropy magnetic behavior. In addition, the various thicknesses (t) of the RT-deposited Co{sub 3}Pt films were deposited with different base pressures prior to sputtering. The Kerr rotation loops showed high PMA and out-of-plane squareness (S{sub ⊥}) of ~0.9 were found in low base pressure chamber. Within high base pressure chamber, Co{sub 3}Pt films just show magnetic isotropy behaviors. This study provides a fabrication method for the preparation of high PMA HCP-type Co{sub 3}Pt films on the glass substrate without any underlayer at RT. The results could be the base for future development of RT-deposited magnetic alloy thin film with high PMA. - Highlights: • Fabricated high perpendicular magnetic anisotropy Co{sub 3}Pt thin film on glass substrate. • Prepared HCP Co{sub 3}Pt thin film at room temperature. • The key to enhance the PMA of the Co{sub 3}Pt films. • Thinner film is good to fabricate PMA Co{sub 3}Pt thin films.

Complex permeability and core loss of soft magnetic Fe-based nanocrystalline powder cores

Energy Technology Data Exchange (ETDEWEB)

Füzerová, Jana, E-mail: jana.fuzerova@tuke.sk [Faculty of Mechanical Engineering, Technical University, Letná 1, 042 00 Košice (Slovakia); Füzer, Ján; Kollár, Peter [Institute of Physics, P.J. Šafárik University, Park Angelinum 9, 040 23 Košice (Slovakia); Bureš, Radovan; Fáberová, Mária [Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 043 53 Košice (Slovakia)

2013-11-15

Rapidly quenched ribbons of Fe{sub 73}Cu{sub 1}Nb{sub 3}Si{sub 16}B{sub 7} were ball milled and cryomilled to get powder and warm consolidated to get bulk compacts. The data presented here are relative to different experimental procedures, one corresponding to milling at room temperature (sample R1) and the other corresponding to cryomilling at temperature of liquid nitrogen (sample L1). It was found that the properties of the initial powder influenced the density, the electrical resistivity and electromagnetic properties of the resulting bulk alloys. Permeability and core loss are structure sensitive and depend on factors such as powder size and shape, porosity, purity, and internal stress. Permeability spectra of sample R1 decreases with increasing the frequency and its values are larger than that for sample L1 at low frequencies. On the other hand the permeability of sample L1 remains steady up to 1 kHz and at certain frequency is larger than that for sample R1. Also there are different frequency dependences of the imaginary parts of permeability and loss factor, respectively. The cryomilling of the amorphous ribbon positively influences on the AC magnetic properties at higher frequencies (above 100 Hz) of resulting bulk sample. - Highlights: • We prepared two different amorphous powder vitroperm samples. • We have examined changes in the properties of the bulk samples prepared by compaction. • It was found that properties of the initial powder influence the density, the electrical resistivity and electromagnetic properties of the resulting bulk alloys.

Fabrication of Co thin films using pulsed laser deposition method with or without employing external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Ehsani, M.H., E-mail: Ehsani@semnan.ac.ir [Thin Film Laboratory, Faculty of Physics, Semnan University (Iran, Islamic Republic of); Mehrabad, M. Jalali [Thin Film Laboratory, Faculty of Physics, Semnan University (Iran, Islamic Republic of); Kameli, P. [Department of Physics, Isfahan University of technology, Isfahan 8415683111 (Iran, Islamic Republic of)

2016-11-01

In this work, the external magnetic field effects on growth condition during deposition processes of the Co thin films were studied. Two specimens of Co films with different condition (with and without external magnetic field) were synthesized by pulsed laser deposition method. Structural and magnetic properties of the Co thin films were systematically studied, using atomic force microscope analysis and magnetization measurement, respectively. During the deposition processes, the external applied magnetic field had been provided by a permanent magnet. The experimental results show that the external magnetic field enables one to tune the magnetic properties of the deposited thin films. To clarify this effect, using Multi-Physics COMSOL simulation environment, a study of vapor flux by applied magnetic field during deposition were performed. Comparison between experimental data and output data of the simulation show promising accommodation and approve the existence of a strong correlation between the structural and magnetic properties of the specimens, and deposition rate of Co thin films. - Graphical abstract: Simulation results of the cobalt particles tracing sputtered from the source to substrate with an external magnetic field. Convergence of the particles flux (left) and also the spiral motion of the cobalt particles (right) increase dramatically as they approach the substrate and NdFe35 magnet. - Highlights: • The external magnetic field effects on growth condition during deposition processes of the Co thin films were studied. • Structural and magnetic properties of the Co thin films were systematically studied, using atomic force microscope analysis and magnetization measurement, respectively. • The experimental results show that the external magnetic field enables one to tune the magnetic properties of the deposited thin films. • To clarify this effect, using Multi-Physics COMSOL simulation environment, a study of vapor flux by applied magnetic field

Magnetic properties of Pr-Fe-B thick-film magnets deposited on Si substrates with glass buffer layer

Science.gov (United States)

Nakano, M.; Kurosaki, A.; Kondo, H.; Shimizu, D.; Yamaguchi, Y.; Yamashita, A.; Yanai, T.; Fukunaga, H.

2018-05-01

In order to improve the magnetic properties of PLD-made Pr-Fe-B thick-film magnets deposited on Si substrates, an adoption of a glass buffer layer was carried out. The glass layer could be fabricated under the deposition rate of approximately 70 μm/h on a Si substrate using a Nd-YAG pulse laser in the vacuum atmosphere. The use of the layer enabled us to reduce the Pr content without a mechanical destruction and enhance (BH)max value by approximately 20 kJ/m3 compared with the average value of non-buffer layered Pr-Fe-B films with almost the same thickness. It is also considered that the layer is also effective to apply a micro magnetization to the films deposited on Si ones.

Magnetism and magnetoresistance from different origins in Co/ZnO:Al granular films

Energy Technology Data Exchange (ETDEWEB)

Quan, Zhiyong, E-mail: quanzy@sxnu.edu.cn; Liu, Xia; Song, Zhilin; Xu, Xiaohong, E-mail: xuxh@dns.sxnu.edu.cn

2016-12-01

Co/ZnO:Al granular films were made on glass substrates by sequential magnetron sputter deposition of ultrathin Co layer and ZnO:Al layer at room temperature. The as-deposited films consist of superparamagnetic Co particles dispersed in ZnO:Al (~2% Al) semiconductor matrix. Distinguished magnetoresistance effect at room temperature was obtained in the as-deposited films, which obviously reduced after annealing due to the growth of Co particles. The size of important magnetic particles was analyzed by Langevin function for hysteresis loops and magnetoresistance curves at room temperature. It was found that small magnetic particle contribute to magnetoresistance behavior and large particles dominate the room temperature magnetism in Co/ZnO:Al granular films.

Magnetic Composite Thin Films of FexOy Nanoparticles and Photocrosslinked Dextran Hydrogels

International Nuclear Information System (INIS)

Brunsen, Annette; Utech, Stefanie; Maskos, Michael; Knoll, Wolfgang; Jonas, Ulrich

2012-01-01

Magnetic hydrogel composites are promising candidates for a broad field of applications from medicine to mechanical engineering. Here, surface-attached composite films of magnetic nanoparticles (MNP) and a polymeric hydrogel (HG) were prepared from magnetic iron oxide nanoparticles and a carboxymethylated dextran with photoreactive benzophenone substituents. A blend of the MNP and the dextran polymer was prepared by mixing in solution, and after spin-coating and drying the blend film was converted into a stable MNP–HG composite by photocrosslinking through irradiation with UV light. The bulk composite material shows strong mobility in a magnetic field, imparted by the MNPs. By utilizing a surface layer of a photoreactive adhesion promoter on the substrates, the MNP–HG films were covalently immobilized during photocrosslinking. The high stability of the composite was documented by rinsing experiments with UV–Vis spectroscopy, while surface plasmon resonance and optical waveguide mode spectroscopy was employed to investigate the swelling behavior in dependence of the nanoparticle concentration, the particle type, and salt concentration. - Highlights: ► blending of iron oxide nanoparticles with photocrosslinkable carboxymethyldextran. ► UV irradiation of blend yields surface-attached, magnetic hydrogel films. ► film characterization by surface plasmon resonance/optical waveguide spectroscopy. ► swelling decreases with increasing nanoparticle content. ► swelling decreases with increasing NaCl salt concentration in the aqueous medium.

Magnetism of coherent Co and Ni thin films on Cu(111) and Au(111) substrates: An ab initio study

Energy Technology Data Exchange (ETDEWEB)

Zelený, Martin, E-mail: zeleny@fme.vutbr.cz; Dlouhý, Ivo

2017-02-15

We present an ab initio study of structural and magnetic properties of coherent Co and Ni thin films on Cu(111) and Au(111) substrates with thicknesses of up to 6 monolayers. All studied films on Cu(111) substrates prefer structures close their ground state (hcp for Co and fcc for Ni), whereas only the hcp stacking sequence has been found for both films on Au(111) substrates. All studied films exhibit instability of the first monolayer with respect to decomposition into 2-monolayer- or 3-monolayer-high islands, which is in agreement with experimental findings. All studied films are also ferromagnetic, nevertheless the Ni/Cu(111) films reduce their magnetic moments in the layer adjacent to the substrate due to a stronger Cu–Ni interaction at the interface. The magnetic anisotropy of a Co film does not depend on the film thickness: all the studied Co/Au(111) films exhibit a perpendicular magnetic anisotropy, whereas all the Co/Cu(111) films prefer in-plane magnetization. On the other hand, both Ni films change their preference for in-plane orientation of their easy axis to out-of-plane orientation at a critical thickness of 2 monolayers, however, the magnetic anisotropy energies for films thicker than 1 monolayer are smaller than 1 meV/Ni atom. These behaviors of magnetic anisotropy do not depend on the structure of the studied films. - Highlights: • All films exhibit instability of the first monolayer and prefer grow in islands. • The Cu–Ni interaction is responsible for reduced Ni magnetic moments in Ni/Cu(111) films. • The Co/Au(111) and Co/Cu(111) films show different orientations of magnetic anisotropy. • The Ni films exhibit in-plane magnetization only for single monolayer. • Behaviors of magnetic anisotropy do not depend on the structure of the studied films.

Multiferroic BiFeO{sub 3} thin films: Structural and magnetic characterization

Energy Technology Data Exchange (ETDEWEB)

Ali, Z. [Physics Department, Faculty of Science (Girls Branch), Al-Azhar University, Cairo (Egypt); Atta, A. [National Center for Radiation Research and Technology (NCRRT), Nasr City, Cairo (Egypt); Abbas, Y. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Sedeek, K.; Adam, A.; Abdeltwab, E. [Physics Department, Faculty of Science (Girls Branch), Al-Azhar University, Cairo (Egypt)

2015-02-27

BiFeO{sub 3} (BFO) film has been deposited on indium tin oxide (ITO) substrate by a simple sol–gel spin-coating technique. The crystal phase composition, surface morphology, topography and magnetization measurements of the BFO thin film were investigated using grazing incidence X-ray diffraction (GIXRD), scanning electronic microscope (SEM), atomic force microscope and vibrating sample magnetometer, respectively. GIXRD analysis revealed that the film was fully crystallized and no impure phase was observed. Cross-section SEM results indicated that compact and homogeneous BFO thin film was deposited on ITO with a thickness of about 180 nm. Moreover, most of A and E-symmetry normal modes of R3c BFO were assigned by Raman spectroscopy. We report here that the pure phase BFO film shows ferromagnetism at room temperature with remarkably high saturation magnetization of 63 kA m{sup −1}. Our results are discussed mainly in correlation with the condition of processing technique and destruction of the spiral spin cycloid at interface layers and grain boundaries. - Highlights: • Multiferroic BiFeO{sub 3} (BFO) thin film was prepared by sol–gel spin-coating method. • BFO film w asdeposited on indium tin oxide substrate with a thickness of 180 nm. • The film exhibits pure rhombohedral perovskite structure. • High saturation magnetization was recorded for our film at room temperature.

Stress analysis, structure and magnetic properties of sputter deposited Ni-Mn-Ga ferromagnetic shape memory thin films

Energy Technology Data Exchange (ETDEWEB)

Annadurai, A. [Department of Physics, PSG College of Technology, Coimbatore 641004 (India); Manivel Raja, M., E-mail: mraja@dmrl.drdo.in [Defense Metallurgical Research Laboratory, Hyderabad 500058 (India); Prabahar, K.; Kumar, Atul [Defense Metallurgical Research Laboratory, Hyderabad 500058 (India); Kannan, M.D.; Jayakumar, S. [Department of Physics, PSG College of Technology, Coimbatore 641004 (India)

2011-11-15

The residual stress instituted in Ni-Mn-Ga thin films during deposition is a key parameter influencing their shape memory applications by affecting its structural and magnetic properties. A series of Ni-Mn-Ga thin films were prepared by dc magnetron sputtering on Si(1 0 0) and glass substrates at four different sputtering powers of 25, 45, 75 and 100 W for systematic investigation of the residual stress and its effect on structure and magnetic properties. The residual stresses in thin films were characterized by a laser scanning technique. The as-deposited films were annealed at 600 deg. C for 1 h in vacuum for structural and magnetic ordering. The compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. The annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. It was found that the increase of sputtering power induced coarsening in thin films. Typical saturation magnetization and coercivity values were found to be 330 emu/cm{sup 3} and 215 Oe, respectively. The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature. - Highlights: > Compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. > Annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. > The highest Curie transition in the films was observed at 365 K. > The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature.

Observation of spin superfluidity: YIG magnetic films and beyond

Science.gov (United States)

Sonin, Edouard

2018-03-01

From topology of the order parameter of the magnon condensate observed in yttrium-iron-garnet (YIG) magnetic films one must not expect energetic barriers making spin supercurrents metastable. But we show that some barriers of dynamical origin are possible nevertheless until the gradient of the phase (angle of spin precession) does not exceed the critical value (analog of the Landau critical velocity in superfluids). On the other hand, recently published claims of experimental detection of spin superfluidity in YIG films and antiferromagnets are not justified, and spin superfluidity in magnetically ordered solids has not yet been experimentally confirmed.

High magnetic field properties of Fe-pnictide thin films

Energy Technology Data Exchange (ETDEWEB)

Kurth, Fritz

2015-11-20

The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

Effect of heat treatment on interface driven magnetic properties of CoFe films

Science.gov (United States)

Singh, Akhilesh Kr.; Hsu, Jen-Hwa

2017-06-01

We report systematic studies on non-magnetic Ta underlayer and cap layer driven microstructural and magnetic properties at a wide temperature range for CoFe films. All the films were grown at room temperature and post annealed at different annealing temperatures (TA = 200 °C, 250 °C, 300 °C, 350 °C, 400 °C and 450 °C). The in-plane magnetic hysteresis (M-H) loops of 10 nm thick CoFe single layer films, grown directly on thermally oxidized Si substrate, exhibit anisotropic nature for TA above 250 °C. However, the CoFe (10 nm) films grown on the 5 nm thick Ta underlayer show reduced anisotropy. Moreover, with underlayer and cap layers (2 nm) the anisotropy is disappeared. The in-plane coercivity (HC) shows a strong variation with TA, underlayer and cap layers. HC increases significantly with Ta underlayer and cap layers. The out of plane M-H loops exhibit increase in the remanence magnetization and squareness with both Ta underlayer and cap layers due to transition of in-plane magnetization component to the out of plane direction. The atomic force microscopic observations revealed that grain/particle size and shape depend strongly on TA and Ta layers. Moreover, a large reduction in the surface roughness is observed with the Ta cap layer. The magnetic domain patterns depend on the TA, and Ta layers. However, for Ta/CoFe/Ta films no clear domains were observed for all the TA. Hence, the Ta cap layers not only protect the CoFe magnetic layer against the heat treatment, but also show a smooth surface at a wide temperature range. These results could be discussed on the basis of random anisotropy model, TA, underlayer and cap layers driven microstructure and magnetization orientation of the CoFe films.

Magnetic properties of thin Ni films measured by a dc SQUID-based magnetic microscope

DEFF Research Database (Denmark)

Snigirev, O.V.; Andreev, K.E.; Tishin, A.M.

1997-01-01

We have applied a scanning HTS (high-temperature superconductor) de SQUID (superconducting quantum interference device) -based magnetic microscope to study the magnetic properties of Au/Ni/Si(100) films in the thickness range from 8 to 200 Angstrom at T = 77 K. A one-domain structure with in...

Effective High-Frequency Permeability of Compacted Metal Powders

Science.gov (United States)

Volkovskaya, I. I.; Semenov, V. E.; Rybakov, K. I.

2018-03-01

We propose a model for determination of the effective complex permeability of compacted metal-powder media. It is based on the equality of the magnetic moment in a given volume of the media with the desired effective permeability to the total magnetic moment of metal particles in the external high-frequency magnetic field, which arises due to excitation of electric eddy currents in the particles. Calculations within the framework of the proposed model allow us to refine the values of the real and imaginary components of the permeability of metal powder compacts in the microwave band. The conditions of applicability of the proposed model are formulated, and their fulfillment is verified for metal powder compacts in the microwave and millimeter wavelength bands.

Strain effect on the magnetic and transport properties of LaCoO3 thin films

Science.gov (United States)

Li, Y.; Peng, S. J.; Wang, D. J.; Wu, K. M.; Wang, S. H.

2018-05-01

LaCoO3 (LCO) has attracted much attention due to the unique magnetic transition and spin transition of Co3+ ions. Epitaxial LCO film exhibits an unexpected ferromagnetism, in contrast to the non-magnetism of bulk LCO. An in-depth study on the property of strained LCO film is of great importance. We have fabricated 30 nm LCO films on various substrates and studied the magnetic and transport properties of films in different strain states (compressed strain for LCO/LaAlO3, tensile strain for LCO/(LaAlO3)0.3(Sr2TaAlO6)0.35, SrTiO3). The in-plane tensiled LCO films exhibit ferromagnetic ground state at 5K and magnetic transition with TC around 85K, while compressed LCO/LaAlO3 film has a negligibly small moment signal. Our results reveal that in-plane tensile strain and tetragonal distortion are much more favorable for stabilizing the FM order in LCO films.

Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps

Energy Technology Data Exchange (ETDEWEB)

Sasada, Ichiro, E-mail: sasada@ence.kyushu-u.ac.jp [Applied Science for Electronics and Materials, Kyushu University, Kasuga (Japan)

2014-05-07

A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

Epitactical FeAl films on sapphire and their magnetic properties

International Nuclear Information System (INIS)

Trautvetter, Moritz

2011-01-01

In the presented thesis epitaxial FeAl thin films on sapphire have been prepared by pulse laser deposition (PLD). The thin films deposited at room temperature exhibits ferromagnetism and subsequent annealing is necessary to transform the thin films to paramagnetic B2-phase, where the transition temperature depends on the crystalline orientation of the sapphire substrate. Alternatively, by deposition at higher substrate temperature the B2-phase is obtained directly. However, morphology of the FeAl film is influenced by different growth modes resulting from different substrate temperatures. The paramagnetic FeAl films can then be transformed to ferromagnetic phase by successive ion irradiation. Independent of the ion species used for irradiation, the same universal relation between thin films' coercive fields and irradiation damage is identified. The ion irradiation ferromagnetism can be transformed back to paramagnetism by subsequent annealing. The mutual transition between ferromagnetic and paramagnetic phases has been performed several times and shows full reversibility. The ferromagnetic phase induced by Kr + irradiation exhibits structural relaxation, where the saturate magnetization of FeAl thin film gradually decreases in several days. Later, ion irradiation has been performed selectively on defined areas of the thin film with the help of an unconventional lithography technique. The subsequent thin film is composed of ordered hexagonal array of ferromagnetic nano-cylinders separated by a paramagnetic matrix, suggesting a promising system for magnetic data storage. (orig.)

Critical behaviour of magnetic thin film with Heisenberg spin-S model

International Nuclear Information System (INIS)

Masrour, R.; Hamedoun, M.; Bouslykhane, K.; Hourmatallah, A.; Benzakour, N.; Benyoussef, A.

2009-01-01

The magnetic properties of a ferromagnetic thin film of face centered cubic (FCC) lattice with Heisenberg spin-S are examined using the high-temperature series expansions technique extrapolated with Pade approximations method. The critical reduced temperature of the system τ c is studied as function of thickness of the film and the exchange interactions in the bulk, and within the surfaces J b , J s and J perpendicular respectively. A critical value of surface exchange interaction above which surface magnetism appears is obtained. The dependence of the reduced critical temperature on the film thickness L has been investigated.

Microwave study of magnetic field penetration parallel to thin niobium films

International Nuclear Information System (INIS)

Grbic, M.S.; Janjusevic, D.; Pozek, M.; Dulcic, A.; Wagner, T.

2007-01-01

Complex conductivity of high quality niobium thin films has been investigated by microwave technique in parallel static magnetic field. For the 40 nm thick film no vortices can be formed and the microwave penetration is defined by the strength of the superconducting order parameter which varies with the applied magnetic field. 160 nm thick measured film allows formation of two rows of vortices. Microwave dissipiation is dominated by dynamics of vortices which is strongly affected by size effects. Results have been compared with the generalised models of complex conductivity for low-dimensional superconductor in mixed state following earlier considerations by other authors

Effect of thickness on structure, microstructure, residual stress and soft magnetic properties of DC sputtered Fe65Co35 soft magnetic thin films

International Nuclear Information System (INIS)

Prasanna Kumari, T.; Manivel Raja, M.; Kumar, Atul; Srinath, S.; Kamat, S.V.

2014-01-01

The effect of film thickness on structure, microstructure, residual stress and soft magnetic properties of Fe 65 Co 35 thin films deposited on Si(001) and MgO(001) substrates was investigated by varying film thickness from 30 to 600 nm. X-ray diffraction studies showed that the FeCo films are polycrystalline in the as-deposited condition irrespective of deposition on Si or MgO substrate. The microstructure of films consisted of spherical grains for 30 nm film thickness and columnar grains for all other film thicknesses. The grain size for the films was found to increase from 15 to 50 nm with increasing film thickness. The sputtered films also exhibited tensile residual stresses with the magnitude of stress decreasing with increasing film thickness. The Fe 65 Co 35 films deposited on both substrates also exhibited very good in-plane soft magnetic properties with a saturation magnetization 4πM s of ∼23.6–23.8 kG and coercivity of ∼27–30 Oe without any under-layer only for films with thickness of 30 nm. For all other thicknesses, these films exhibited a significantly higher coercivity. The observed variations in soft magnetic properties with film thickness were explained in terms of residual stress and microstructure of the films. - Highlights: • Spherical grain morphology transformed to columnar above 30 nm film thickness. • Sputtered films exhibited tensile residual stresses decreasing with film thickness. • An in-plane coercivity of ∼27–30 Oe was achieved without any under-layer

Microstructure and magnetic properties of Co-doped ZnO films deposited by gas flow sputtering

Energy Technology Data Exchange (ETDEWEB)

Sakuma, H., E-mail: hsakuma@cc.utsunomiya-u.ac.jp [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Watanabe, Y. [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Aramaki, K.; Yun, K.S. [Sony Chemical and Information Device Corporation, 1078 Kamiishikawa, Kanuma 322-8503 (Japan); Ishii, K. [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Ikeda, Y.; Kondo, H. [Sony Chemical and Information Device Corporation, 1078 Kamiishikawa, Kanuma 322-8503 (Japan)

2010-10-15

Co-doped ZnO films with a Co concentration of 8-20 at.% were fabricated using the low-energy process of gas flow sputtering. X-ray diffraction, X-ray photoelectron spectroscopy, and optical absorption measurements revealed that the Co ions replace Zn ions in the ZnO matrix and that the Co ions have an oxidation state of 2+. The magnetic properties of the film depend on the Co concentration. The plots of magnetization and inverse susceptibility vs. temperature indicate that the film with a high Co concentration (20 at.%) contains a ferromagnetic component, while that with a low Co concentration (8 at.%) contains an antiferromagnetic component. The film with an intermediate Co concentration (10 at.%) contains a ferromagnetic component with a low Curie temperature. Hysteresis was not found in magnetization curves for all the samples, including the sample at 5 K. The films exhibited a high resistivity of 4 x 10{sup 7}-2 x 10{sup 8} {Omega} cm at room temperature, and carrier-mediated magnetism is not likely to be applicable for the mechanisms of the magnetism in the films.

Microstructure and magnetic properties of Co-doped ZnO films deposited by gas flow sputtering

International Nuclear Information System (INIS)

Sakuma, H.; Watanabe, Y.; Aramaki, K.; Yun, K.S.; Ishii, K.; Ikeda, Y.; Kondo, H.

2010-01-01

Co-doped ZnO films with a Co concentration of 8-20 at.% were fabricated using the low-energy process of gas flow sputtering. X-ray diffraction, X-ray photoelectron spectroscopy, and optical absorption measurements revealed that the Co ions replace Zn ions in the ZnO matrix and that the Co ions have an oxidation state of 2+. The magnetic properties of the film depend on the Co concentration. The plots of magnetization and inverse susceptibility vs. temperature indicate that the film with a high Co concentration (20 at.%) contains a ferromagnetic component, while that with a low Co concentration (8 at.%) contains an antiferromagnetic component. The film with an intermediate Co concentration (10 at.%) contains a ferromagnetic component with a low Curie temperature. Hysteresis was not found in magnetization curves for all the samples, including the sample at 5 K. The films exhibited a high resistivity of 4 x 10 7 -2 x 10 8 Ω cm at room temperature, and carrier-mediated magnetism is not likely to be applicable for the mechanisms of the magnetism in the films.

Effect of heat treatment on interface driven magnetic properties of CoFe films

Energy Technology Data Exchange (ETDEWEB)

Singh, Akhilesh Kr., E-mail: drakhintu@gmail.com; Hsu, Jen-Hwa

2017-06-15

Highlights: • Ta underlayer and cap layer dependent anisotropy nature in thin CoFe films. • Thin Ta layer induces the magnetization component along normal to the film plane. • Heat treatment and Ta layers driven surface morphology, roughness and grain size. • Roughness reduces more than an order of magnitude with 2 nm Ta cap layer. • H{sub C}, domain patterns and domain size depend on Ta layers and heat treatment. - Abstract: We report systematic studies on non-magnetic Ta underlayer and cap layer driven microstructural and magnetic properties at a wide temperature range for CoFe films. All the films were grown at room temperature and post annealed at different annealing temperatures (T{sub A} = 200 °C, 250 °C, 300 °C, 350 °C, 400 °C and 450 °C). The in-plane magnetic hysteresis (M–H) loops of 10 nm thick CoFe single layer films, grown directly on thermally oxidized Si substrate, exhibit anisotropic nature for T{sub A} above 250 °C. However, the CoFe (10 nm) films grown on the 5 nm thick Ta underlayer show reduced anisotropy. Moreover, with underlayer and cap layers (2 nm) the anisotropy is disappeared. The in-plane coercivity (H{sub C}) shows a strong variation with T{sub A}, underlayer and cap layers. H{sub C} increases significantly with Ta underlayer and cap layers. The out of plane M–H loops exhibit increase in the remanence magnetization and squareness with both Ta underlayer and cap layers due to transition of in-plane magnetization component to the out of plane direction. The atomic force microscopic observations revealed that grain/particle size and shape depend strongly on T{sub A} and Ta layers. Moreover, a large reduction in the surface roughness is observed with the Ta cap layer. The magnetic domain patterns depend on the T{sub A}, and Ta layers. However, for Ta/CoFe/Ta films no clear domains were observed for all the T{sub A}. Hence, the Ta cap layers not only protect the CoFe magnetic layer against the heat treatment, but also

Effect of heat treatment on interface driven magnetic properties of CoFe films

International Nuclear Information System (INIS)

Singh, Akhilesh Kr.; Hsu, Jen-Hwa

2017-01-01

Highlights: • Ta underlayer and cap layer dependent anisotropy nature in thin CoFe films. • Thin Ta layer induces the magnetization component along normal to the film plane. • Heat treatment and Ta layers driven surface morphology, roughness and grain size. • Roughness reduces more than an order of magnitude with 2 nm Ta cap layer. • H C , domain patterns and domain size depend on Ta layers and heat treatment. - Abstract: We report systematic studies on non-magnetic Ta underlayer and cap layer driven microstructural and magnetic properties at a wide temperature range for CoFe films. All the films were grown at room temperature and post annealed at different annealing temperatures (T A = 200 °C, 250 °C, 300 °C, 350 °C, 400 °C and 450 °C). The in-plane magnetic hysteresis (M–H) loops of 10 nm thick CoFe single layer films, grown directly on thermally oxidized Si substrate, exhibit anisotropic nature for T A above 250 °C. However, the CoFe (10 nm) films grown on the 5 nm thick Ta underlayer show reduced anisotropy. Moreover, with underlayer and cap layers (2 nm) the anisotropy is disappeared. The in-plane coercivity (H C ) shows a strong variation with T A , underlayer and cap layers. H C increases significantly with Ta underlayer and cap layers. The out of plane M–H loops exhibit increase in the remanence magnetization and squareness with both Ta underlayer and cap layers due to transition of in-plane magnetization component to the out of plane direction. The atomic force microscopic observations revealed that grain/particle size and shape depend strongly on T A and Ta layers. Moreover, a large reduction in the surface roughness is observed with the Ta cap layer. The magnetic domain patterns depend on the T A , and Ta layers. However, for Ta/CoFe/Ta films no clear domains were observed for all the T A . Hence, the Ta cap layers not only protect the CoFe magnetic layer against the heat treatment, but also show a smooth surface at a wide

Oxygen pressure-tuned epitaxy and magnetic properties of magnetite thin films

Energy Technology Data Exchange (ETDEWEB)

Zhang, Junran [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu, Wenqing [York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom); Zhang, Minhao; Zhang, Xiaoqian; Niu, Wei; Gao, Ming [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wang, Xuefeng, E-mail: xfwang@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Du, Jun [School of Physics, Nanjing University, Nanjing 210093 (China); Zhang, Rong [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Yongbing, E-mail: ybxu@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom)

2017-06-15

Highlights: • Quasi-2D Fe{sub 3}O{sub 4} films were obtained by PLD. • RHEED under different oxygen pressure were observed. • Influence of oxygen pressure on Fe{sub 3}O{sub 4} films were investigated. • Epitaxy and magnetic properties were tuned by oxygen pressure. • The ratio of Fe{sup 2+}/Fe{sup 3+} fitted by XPS is the tuned factor of M{sub s}. - Abstract: Quasi-two-dimensional magnetite epitaxial thin films have been synthesized by pulsed laser deposition technique at various oxygen pressures. The saturation magnetizations of the magnetite films were found to decrease from 425 emu/cm{sup 3}, which is close to the bulk value, to 175 emu/cm{sup 3} as the growth atmospheres varying from high vacuum (∼1 × 10{sup −8} mbar) to oxygen pressure of 1 × 10{sup −3} mbar. The ratio of the Fe{sup 3+} to Fe{sup 2+} increases from 2 to 2.7 as oxygen pressure increasing shown by XPS fitting, which weakens the net magnetic moment generated by Fe{sup 2+} at octahedral sites as the spins of the Fe{sup 3+} ions at octahedral and tetrahedral sites are aligned in antiparallel. The results offer direct experimental evidence of the influence to the Fe{sup 3+}/Fe{sup 2+} ratio and the magnetic moment in magnetite epitaxy films by oxygen pressure, which is significant for spintronic applications.

Chemical composition, water vapor permeability, and mechanical properties of yuba film influenced by soymilk depth and concentration.

Science.gov (United States)

Zhang, Siran; Lee, Jaesang; Kim, Yookyung

2018-03-01

Yuba is a soy protein-lipid film formed during heating of soymilk. This study described yuba as an edible film by analyzing its chemical composition, water vapor permeability (WVP), and mechanical properties. Three yuba films were prepared by using different concentrations and depths of soymilk: HS (86 g kg -1 and 2.3 cm), LS (70 g kg -1 and 2.3 cm), and LD (70 g kg -1 and 3.0 cm). As yuba was successively skimmed, the protein, lipid, and SH content decreased, but carbohydrate and SS content increased. Though both the initial concentration and the depth of soymilk affect the properties of the films, the depth of soymilk influences WVP and tensile strength (TS) more. The WVP of the HS and LS changed the least (13-17 g mm kPa -1 m -2 day 1 ), while that of the LD changed the most (13-35 g mm kPa -1 m -2 day -1 ). There were no differences (P > 0.05) in the TS between the HS and LS. LD had the greatest decrease of TS and the lowest TS among the groups. The earlier the yuba films were collected, the greater the elongation of the films was: 129% (HS), 113% (LS), and 155% (LD). The initial concentration and the depth of soymilk changed the chemical composition and structure of the yuba films. The LS yuba produced more uniform edible films with good mechanical properties. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Magnetic properties of epitaxial MnAs thin films on GaAs (001)

CERN Document Server

Park, Y S

2000-01-01

The magnetic properties of two types of epitaxial MnAs films on GaAs (001) substrates in the thickness range of 20 approx 200 nm were studied. Using longitudinal a magneto-optical Kerr-effect(MOKE) apparatus at lambda=632.8 nm, we determined the Curie temperatures of the 100-nm thick films to be 54.0+-0.5 .deg. C and 63.7+-0.5 .deg. C for type A films and type B films, respectively. The observed Curie temperatures corresponded to increases of 36.8 .deg. C and 33.9 .deg. C per one percent increase in the unit cell volume for type A and B, respectively. The normalized maximum MOKE signal from the type A film exhibited a first-order-like magnetic transition while that of type B underwent a second-order-like transition. These different behaviors between types A and B stem from different residual stresses being exerted on the hexagonal phase. Utilizing a Foner-type vibrating sample magnetometer at room temperature, we examined the thickness dependence of the coercive force and the saturation magnetization of the f...

Growth and structure of Co/Au magnetic thin films

International Nuclear Information System (INIS)

Marsot, N.

1999-01-01

We have studied the growth and the crystallographic structure of magnetic ultra thin cobalt/gold films (Co/Au), in order to investigate the correlations between their magnetic and structural properties. Room temperature (R.T.) Co growth on Au (111) proceeds in three stages. Up to 2 Co monolayers (ML), a bilayer island growth mode is observed. Between 2 and 5 ML, coalescence of the islands occurs, covering the substrate surface and a Co/Au mixing is observed resulting from the de-construction of the Herringbone reconstruction. Finally, beyond 5 ML, the CoAu mixing is buried and the Co growth continues in a 3-D growth. Annealing studies at 600 K on this system show a smoothing effect of the Co film, and at the same time, segregation of Au atoms. The quality of the Co/Au interface (sharpness) is not enhanced by the annealing. The local order was studied by SEXAFS and the long range order by GIXRD showing that the Co film has a hexagonal close packed structure, with an easy magnetization axis perpendicular to the surface. From a local order point of view, the Co grows with an incoherent epitaxy and keeps its own bulk parameters. The GIXRD analysis shows a residual strain in the Co film of 4%. The difference observed between the local order analysis and the long range order results is explained in terms of the low dimensions of the diffracting domains. The evolution of film strains, as a function of the Co coverage, shows a marked deviation from the elastic strain theory. Modification of the strain field in the Co film as a function of the Au coverage is studied by GIXRD analysis. The Au growth study, at R.T., shows no evidence of a Au/Co mixing in the case of the Au/Co interface. The Au overlayer adopts a twinned face centred cubic structure on the rough Co film surface. (author)

Composition, structure and magnetic properties of sputter deposited Ni-Mn-Ga ferromagnetic shape memory thin films

Energy Technology Data Exchange (ETDEWEB)

Annadurai, A.; Nandakumar, A.K.; Jayakumar, S.; Kannan, M.D. [Thin Film Center, Department of Physics, PSG College of Technology, Coimbatore 641004 (India); Manivel Raja, M.; Bysak, S. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad, Andhra Pradesh 500 058 (India); Gopalan, R. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad, Andhra Pradesh 500 058 (India)], E-mail: rg_gopy@yahoo.com; Chandrasekaran, V. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad, Andhra Pradesh 500 058 (India)

2009-03-15

Polycrystalline Ni-Mn-Ga thin films were deposited by the d.c. magnetron sputtering on well-cleaned substrates of Si(1 0 0) and glass at a constant sputtering power of 36 W. We report the influence of sputtering pressure on the composition, structure and magnetic properties of the sputtered thin films. These films display ferromagnetic behaviour only after annealing at an elevated temperature and a maximum saturation magnetization of 335 emu/cc was obtained for the films investigated. Evolution of martensitic microstructure was observed in the annealed thin films with the increase of sputtering pressure. The thermo-magnetic curves exhibited only magnetic transition in the temperature range of 339-374 K. The thin film deposited at high sputtering pressure of 0.025 mbar was found to be ordered L2{sub 1} austenitic phase.

Ferrimagnetic Tb-Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

Directory of Open Access Journals (Sweden)

Birgit eHebler

2016-02-01

Full Text Available Ferrimagnetic rare earth - transition metal Tb-Fe alloy thin films exhibit a variety of different magnetic properties, which depends strongly on composition and temperature. In this study, first the influence of the film thickness (5 - 85 nm on the sample magnetic properties was investigated in a wide composition range between 15 at.% and 38 at.% of Tb. From our results, we find that the compensation point, remanent magnetization, and magnetic anisotropy of the Tb-Fe films depend not only on the composition but also on the thickness of the magnetic film up to a critical thickness of about 20-30 nm. Beyond this critical thickness, only slight changes in magnetic properties are observed. This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short range order. As a result, a more collinear alignment of the distributed magnetic moments of Tb along the out-of-plane direction with film thickness is obtained. This increasing contribution of the Tb sublattice magnetization to the total sample magnetization is equivalent to a sample becoming richer in Tb and can be referred to as an effective composition. Furthermore, the possibility of all-optical switching, where the magnetization orientation of Tb-Fe can be reversed solely by circularly polarized laser pulses, was analyzed for a broad range of compositions and film thicknesses and correlated to the underlying magnetic properties.

Thick film magnetic nanoparticulate composites and method of manufacture thereof

Science.gov (United States)

Ma, Xinqing (Inventor); Zhang, Yide (Inventor); Ge, Shihui (Inventor); Zhang, Zongtao (Inventor); Yan, Dajing (Inventor); Xiao, Danny T. (Inventor)

2009-01-01

Thick film magnetic/insulating nanocomposite materials, with significantly reduced core loss, and their manufacture are described. The insulator coated magnetic nanocomposite comprises one or more magnetic components, and an insulating component. The magnetic component comprises nanometer scale particles (about 1 to about 100 nanometers) coated by a thin-layered insulating phase. While the intergrain interaction between the immediate neighboring magnetic nanoparticles separated by the insulating phase provides the desired soft magnetic properties, the insulating material provides high resistivity, which reduces eddy current loss.

Dynamical formation of spatially localized arrays of aligned nanowires in plastic films with magnetic anisotropy.

Science.gov (United States)

Fragouli, Despina; Buonsanti, Raffaella; Bertoni, Giovanni; Sangregorio, Claudio; Innocenti, Claudia; Falqui, Andrea; Gatteschi, Dante; Cozzoli, Pantaleo Davide; Athanassiou, Athanassia; Cingolani, Roberto

2010-04-27

We present a simple technique for magnetic-field-induced formation, assembling, and positioning of magnetic nanowires in a polymer film. Starting from a polymer/iron oxide nanoparticle casted solution that is allowed to dry along with the application of a weak magnetic field, nanocomposite films incorporating aligned nanocrystal-built nanowire arrays are obtained. The control of the dimensions of the nanowires and of their localization across the polymer matrix is achieved by varying the duration of the applied magnetic field, in combination with the evaporation dynamics. These multifunctional anisotropic free-standing nanocomposite films, which demonstrate high magnetic anisotropy, can be used in a wide field of technological applications, ranging from sensors to microfluidics and magnetic devices.

Perpendicular magnetic anisotropy and magnetization dynamics in oxidized CoFeAl films

Science.gov (United States)

Wu, Di; Zhang, Zhe; Li, Le; Zhang, Zongzhi; Zhao, H. B.; Wang, J.; Ma, B.; Jin, Q. Y.

2015-07-01

Half-metallic Co-based full-Heusler alloys with perpendicular magnetic anisotropy (PMA), such as Co2FeAl in contact with MgO, are receiving increased attention recently due to its full spin polarization for high density memory applications. However, the PMA induced by MgO interface can only be realized for very thin magnetic layers (usually below 1.3 nm), which would have strong adverse effects on the material properties of spin polarization, Gilbert damping parameter, and magnetic stability. In order to solve this issue, we fabricated oxidized Co50Fe25Al25 (CFAO) films with proper thicknesses without employing the MgO layer. The samples show controllable PMA by tuning the oxygen pressure (PO2) and CFAO thickness (tCFAO), large perpendicular anisotropy field of ~8.0 kOe can be achieved at PO2 = 12% for the sample of tCFAO = 2.1 nm or at PO2 = 7% for tCFAO = 2.8 nm. The loss of PMA at thick tCFAO or high PO2 results mainly from the formation of large amount of CoFe oxides, which are superparamagnetic at room temperature but become hard magnetic at low temperatures. The magnetic CFAO films, with strong PMA in a relatively wide thickness range and small intrinsic damping parameter below 0.028, would find great applications in developing advanced spintronic devices.

Calculation of electromagnetic constitutive parameters of insulating magnetic materials with conducting inclusions

Energy Technology Data Exchange (ETDEWEB)

Kuster, E.; Moore, R.; Lust, L.; Kemper, P. [Georgia Inst. of Tech., Atlanta, GA (United States)

1996-12-31

A Method of Moments (MoM) electromagnetic model of percolating conducting films was applied to calculate the effective parameters of the composite formed by conducting inclusions placed within a dispersive magnetic but nondispersive dielectric matrix. The MoM calculations demonstrate a coupling between the magnetic properties of the matrix and the effective composite permittivity and frequency dispersion of the composite. The coupling of permittivity and permeability is observed near the percolation threshold of the composite and for high conductivity inclusions. The prediction agrees with physical expectations since near percolation the conduction correlation length dominates the effective permittivity of the composite and this correlation length is determined by both the permittivity and permeability of the composite.

The influence of the surface topography on the magnetization dynamics in soft magnetic thin films

NARCIS (Netherlands)

Craus, CB; Palasantzas, G; Chezan, AR; De Hosson, JTM; Boerma, DO; Niesen, L

2005-01-01

In this work we study the influence of surface roughness on the magnetization dynamics of soft magnetic nanocrystalline Fe-Zr-N thin films deposited (under identical conditions) onto a Si oxide, a thin polymer layer, and a thin Cu layer. The substrate temperature during deposition was approximately

Magnetic and structural study of Cu-doped TiO2 thin films

International Nuclear Information System (INIS)

Torres, C.E. Rodriguez; Golmar, F.; Cabrera, A.F.; Errico, L.; Navarro, A.M. Mudarra; Renteria, M.; Sanchez, F.H.; Duhalde, S.

2007-01-01

Transparent pure and Cu-doped (2.5, 5 and 10 at.%) anatase TiO 2 thin films were grown by pulsed laser deposition technique on LaAlO 3 substrates. The samples were structurally characterized by X-ray absorption spectroscopy and X-ray diffraction. The magnetic properties were measured using a SQUID. All films have a FM-like behaviour. In the case of the Cu-doped samples, the magnetic cycles are almost independent of the Cu concentration. Cu atoms are forming CuO and/or substituting Ti in TiO 2 . The thermal treatment in air promotes the CuO segregation. Since CuO is antiferromagnetic, the magnetic signals present in the films could be assigned to Cu substitutionally replacing cations in TiO 2

Octahedral tilt independent magnetism in confined GdTiO3 films

Science.gov (United States)

Need, R. F.; Isaac, B. J.; Kirby, B. J.; Borchers, J. A.; Stemmer, S.; Wilson, Stephen D.

2018-03-01

Low temperature polarized neutron reflectometry measurements are presented, exploring the evolution of ferrimagnetism in thin GdTiO3 films embedded within a SrTiO3 matrix. In GdTiO3 films thinner than ˜4 nm, the TiO6 octahedral tilts endemic to GdTiO3 coherently relax toward the undistorted, cubic phase of SrTiO3. Our measurements indicate that the ferrimagnetic state within the GdTiO3 layers survives as these TiO6 octahedral tilts are suppressed. Furthermore, our data suggest that layers of suppressed magnetization (i.e., magnetic dead layers) develop within the GdTiO3 layer at each GdTiO3/SrTiO3 interface and explain the apparent magnetization suppression observed in thin GdTiO3 films when using volume-averaged techniques. Our data show that the low temperature magnetic moment inherent to the core GdTiO3 layers is only weakly impacted as the octahedral tilt angles are suppressed by more than 50% and the t2 g bandwidth is dramatically renormalized.

Controllable deposition of gadolinium doped ceria electrolyte films by magnetic-field-assisted electrostatic spray deposition

International Nuclear Information System (INIS)

Ksapabutr, Bussarin; Chalermkiti, Tanapol; Wongkasemjit, Sujitra; Panapoy, Manop

2013-01-01

This paper describes a simple and low-temperature approach to fabrication of dense and crack-free gadolinium doped ceria (GDC) thin films with controllable deposition by a magnetic-field-assisted electrostatic spray deposition technique. The influences of external permanent magnets on the deposition of GDC films were investigated. The coating area deposited using two magnets with the same pole arrangement decreased in comparison with the case of no magnets, whereas the largest deposition area was obtained in the system of the opposite poles. Analysis of as-deposited films at 450 °C indicated the formation of uniform, smooth and dense thin films with a single-phase fluorite structure. The films produced in the system using same poles were thicker, smaller in crystallite size and smoother than those fabricated under other conditions. Additionally, the GDC film deposited using the same pole arrangement showed the maximum in electrical conductivity of about 2.5 × 10 −2 S/cm at a low operating temperature of 500 °C. - Highlights: • Magnetic-field-assisted electrostatic spray allows a controllable coating. • Dense, crack-free thin films were obtained at low process temperature of 450 °C. • Control of deposition, thickness and uniformity is easy to achieve simultaneously. • Films from the same pole were thicker, smaller in crystal size and smoother. • The maximum conductivity of doped ceria film was 2.5 × 10 −2 S/cm at 500 °C

Fabrication and magnetization measurement of Ni thin films on silicon substrate by electrodeposition

Energy Technology Data Exchange (ETDEWEB)

Tang Yang [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences (China); Zhao Dongxu [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China)], E-mail: dxzhao2000@yahoo.com.cn; Shen Dezhen; Zhang Jiying; Li Binghui; Lu Youming; Fan Xiwu [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China)

2008-02-29

Ni thin films were electrodeposited on n-Si (100) substrate from the electrolytes containing Ni(CH{sub 3}COO){sub 2} and CH{sub 3}COONH{sub 4} at room temperature. The scanning electron microscope images of the films reveals the uniform distribution of the nickel all over the substrate surface, which illustrates that the fine Ni films on large scales could be obtained through the method of electrodeposition. Vibrating sample magnetometer measurement with the applied field parallel to the surface shows obvious hysteresis loops of the magnetic thin films. The morphology and magnetism of the Ni thin films evolves with the deposition time increasing. The effect of deposition conditions on the properties of the Ni thin films is investigated.

The rotational hysteresis losses in thin films with unidirectional magnetic anisotropy

Science.gov (United States)

Mucha, J. M.; Vatskichev, L.; Vatskicheva, M.

1992-03-01

Using the Planar Hall Effect (PHE) the rotational hysteresis losses in NiFeGe thin magnetic films were measured. The calculation of the critical field for magnetization and rotational hysteresis losses based on extended Stoner-Wohlfarth theory including an exchange magnetic field is given.

Magnetic field dependence of the current flowing in the spin-coated chlorophyll thin films

Science.gov (United States)

Aji, J. R. P.; Kusumandari; Purnama, B.

2018-03-01

The magnetic dependence of the current flowing in the spin coated chlorophyll films on a patterned Cu PCB substrate has been presented. Chlorophyll was isolated from Spirulina sp and deposited by spin coated methods. The reducing of current by the change of magnetic field (magneto conductance effect) was performed by inducing the magnetic field parallel to the inplane of film at room temp. The magnetoconductance ratio decreases as the increase of voltage. It was indicated that the origin of carrier charge in chlorophyll films should be different with the carrier charge injection (electron).

Effect of adding Cr on magnetic properties and metallic behavior in MnTe film

International Nuclear Information System (INIS)

Wang, Z.H.; Geng, D.Y.; Gong, W.J.; Li, J.; Li, Y.B.; Zhang, Z.D.

2012-01-01

Mn 1−x Cr x Te films with x = 0, 0.02, and 0.05 was synthesized by pulsed laser deposition and crystallize in hexagonal NiAs-type structure. The spin glass behavior predicted before by Monte Carlo calculation is observed in the MnTe film. This behavior is destroyed by adding Cr in the MnTe film. The temperature dependence of magnetization shows a sharp rise at around 66 K, due to the magneto-elastic coupling. Metallic behavior is observed in the MnTe film in the temperature range 120–220 K, which is ascribed to the magnetic ordering. The metallic behavior disappears with adding Cr, because adding Cr ions destroys the magnetic ordering which is mediated by the sp–d exchange interaction between the Cr ions. - Highlights: ► Mn 1−x Cr x Te films with NiAs-type structure was prepared by pulsed laser deposition. ► The spin glass behavior was observed in MnTe film at low temperature. ► The spin glass behavior was destroyed by adding Cr. ► The temperature dependence of magnetization showed a sharp rise at around 66 K. ► Metallic behavior was observed in MnTe film, which disappeared by adding Cr.

Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

Science.gov (United States)

Kalaivani, A.; Senguttuvan, G.; Kannan, R.

2018-03-01

Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

Electronic and magnetic properties of TTF and TCNQ covered Co thin films

Energy Technology Data Exchange (ETDEWEB)

Geijn, Elmer van, E-mail: e.vangeijn@utwente.nl; Wang, Kai; Jong, Michel P. de [NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

2016-05-07

Interfacial effects like orbital hybridization and charge transfer strongly influence the transfer of spins from ferromagnetic metals to organic semiconductors and can lead to the formation of interfacial states with distinct magnetic properties. The changes in the electronic and magnetic properties of a thin Co film upon adsorption of a layer of either the molecular organic electron donor tetrathiafulvalene (TTF) or the acceptor tetracyanoquinodimethane (TCNQ) have been investigated by X-ray absorption spectroscopy and X-ray magnetic circular dichroism using synchrotron radiation. Clear differences between the spectra of the adsorbed molecules and the neutral molecules show the hybridization of the molecular orbitals with the Co interface. Deposition of both organic materials leads to a small increase of the ratio of the orbital magnetic moment to the spin magnetic moment of the Co atoms at the interface. The main effect of overlayer deposition is a modification of the magnetic hysteresis of the Co film: The TCNQ slightly reduces the coercivity of the Co, while the TTF increases the coercivity by a factor of ∼1.5. These complementary effects of either a molecular organic electron donor or acceptor on the interfacial properties of a metal ferromagnetic thin film are a promising result for the controlled modification of the magnetic structure of hybrid interfaces.

Magnetic properties of laser deposited films of Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

McGuire, T.R.; Dimos, D.; Gupta, A.; Koren, G.; Laibowitz, R.B. (IBM Research Division, T. J. Watson Research Center, P. O. Box 218, Yorktown Heights, New York 10598 (USA))

1990-05-01

Films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} prepared by laser ablation deposition show epitaxial growth on (100) SrTiO{sub 3} substrates with the {ital c} axis perpendicular to the plane of the film. With the magnetic field ({ital H}) parallel to the {ital c} axis, critical currents of up to 40 MA/cm{sup 2} from magnetization measurements are obtained. With {ital H} perpendicular to the {ital c} axis, various magnetization measurements with field cooling in 40 kOe indicated strong pinning effects with a calculated critical current density significantly higher than that observed in the parallel field configuration.

Conductive, magnetic and structural properties of multilayer films

Science.gov (United States)

Kotov, L. N.; Turkov, V. K.; Vlasov, V. S.; Lasek, M. P.; Kalinin, Yu E.; Sitnikov, A. V.

2013-12-01

Composite-semiconductor and composite-dielectric multilayer films were obtained by the ion beam sputtering method in the argon and hydrogen atmospheres with compositions: {[(Co45-Fe45-Zr10)x(Al2O3)y]-[α-Si]}120, {[(Co45-Ta45-Nb10)x(SiO2)y]-[SiO2]}56, {[(Co45-Fe45-Zr10)x(Al2O3)y]-[α-Si:H]}120. The images of surface relief and distribution of the dc current on composite layer surface were obtained with using of atomic force microscopy (AFM). The dependencies of specific electric resistance, ferromagnetic resonance (FMR) fields and width of line on metal (magnetic) phase concentration x and nanolayers thickness of multilayer films were obtained. The characteristics of FMR depend on magnetic interaction among magnetic granules in the composite layers and between the layers. These characteristics depend on the thickness of composite and dielectric or semiconductor nanolayers. The dependences of electric microwave losses on the x and alternating field frequency were investigated.

Structural and magnetic properties of [001] CoCr2O4 thin films

NARCIS (Netherlands)

Guzman, Roger; Heuver, Jeroen; Matzen, Sylvia; Magen, Cesar; Noheda, Beatriz

2017-01-01

The spinel CoCr2O4 (CCO) is one of the few bulk multiferroics with net magnetic moment. However, studies on the properties of CCO thin films are scarce. Here, we investigate the interplay between microstructure and magnetism of a series of CCO epitaxial thin films by means of x-ray diffraction,

Human action pattern monitor for telecare system utilizing magnetic thin film infrared sensor

International Nuclear Information System (INIS)

Osada, H.; Chiba, S.; Oka, H.; Seki, K.

2002-01-01

The magnetic thin film infrared sensor (MFI) is an infrared sensing device utilizing a temperature-sensitive magnetic thin film with marked temperature dependence in the room temperature range. We propose a human action pattern monitor (HPM) constructed with the MFI, without a monitor camera to save the clients' privacy, as a telecare system

Fabrication and characteristics of magnetic field sensors based on nano-polysilicon thin-film transistors

International Nuclear Information System (INIS)

Zhao Xiaofeng; Wen Dianzhong; Zhuang Cuicui; Cao Jingya; Wang Zhiqiang

2013-01-01

A magnetic field sensor based on nano-polysilicon thin films transistors (TFTs) with Hall probes is proposed. The magnetic field sensors are fabricated on 〈100〉 orientation high resistivity (ρ > 500 Ω·cm) silicon substrates by using CMOS technology, which adopt nano-polysilicon thin films with thicknesses of 90 nm and heterojunction interfaces between the nano-polysilicon thin films and the high resistivity silicon substrates as the sensing layers. The experimental results show that when V DS = 5.0 V, the magnetic sensitivities of magnetic field sensors based on nano-polysilicon TFTs with length—width ratios of 160 μm/80 μm, 320 μm/80 μm and 480 μm/80 μm are 78 mV/T, 55 mV/T and 34 mV/T, respectively. Under the same conditions, the magnetic sensitivity of the obtained magnetic field sensor is significantly improved in comparison with a Hall magnetic field sensor adopting silicon as the sensing layers. (semiconductor technology)

Mn doping effect on structure and magnetism of epitaxial (FePt)1-xMnx films

International Nuclear Information System (INIS)

Huang, J.C.A.; Chang, Y.C.; Yu, C.C.; Yao, Y.D.; Hu, Y.M.; Fu, C.M.

2003-01-01

We study the structure and perpendicular magnetism of molecular beam epitaxy grown (FePt) 1-x Mn x films with doping concentration x=0, 1%, 2%, 3%, 4%, and 5%. The (FePt) 1-x Mn x films were made by multilayers growth of [Fe/Pt/Mn]xN at 100 deg. C and annealed at 600 deg. C. X-ray diffraction scans indicate that relatively better L1 0 ordered structure for low Mn doping (x 3%. The perpendicular magnetic anisotropy effect of the (FePt) 1-x Mn x films tends to decrease with the increase of Mn doping for x>1%. However, the x=1% doped films possess slightly better perpendicular magnetic anisotropy effect than the zero doped film. The perpendicular magnetic anisotropy constant are of about 1.3x10 7 and 1.6x10 7 erg/cm 3 for x=0% and x=1%, respectively

Exchange-coupled hard magnetic Fe-Co/CoPt nanocomposite films fabricated by electro-infiltration

Directory of Open Access Journals (Sweden)

Xiao Wen

2017-05-01

Full Text Available This paper introduces a potentially scalable electro-infiltration process to produce exchange-coupled hard magnetic nanocomposite thin films. Fe-Co/CoPt nanocomposite films are fabricated by deposition of CoFe2O4 nanoparticles onto Si substrate, followed by electroplating of CoPt. Samples are subsequently annealed under H2 to reduce the CoFe2O4 to magnetically soft Fe-Co and also induce L10 ordering in the CoPt. Resultant films exhibit 0.97 T saturation magnetization, 0.70 T remanent magnetization, 127 kA/m coercivity and 21.8 kJ/m3 maximum energy density. First order reversal curve (FORC analysis and δM plot are used to prove the exchange coupling between soft and hard magnetic phases.

High current densities in superconducting films from magnetization

International Nuclear Information System (INIS)

McGuire, T.R.; Gupta, A.; Koren, G.; Gross, R.

1990-01-01

Epitaxial thin films of YBa 2 Cu 3 O 7-x made by laser ablation have the CuO planes parallel to the film surface. In the CuO planes critical currents of J C ∼40 x 10 6 amps/cm 2 are found at 5K in zero field. Multi-layered films with Gd replacing Y each .01μm in thickness have J C nearly 140 x 10 6 amps/cm 2 . This higher value is perhaps due to additional point defects. Perpendicular to the CuO planes magnetization studies indicate strong pinning effects attributed to the CuO planes acting as barriers to flux motion

Improving the performance of nickel-coated fluorine-doped tin oxide thin films by magnetic-field-assisted laser annealing

Energy Technology Data Exchange (ETDEWEB)

Li, Bao-jia, E-mail: li_bjia@126.com [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Provincial Key Laboratory of Center for Photon Manufacturing Science and Technology, Jiangsu University, Zhenjiang 212013 (China); Huang, Li-jing [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Jiangsu Provincial Key Laboratory of Center for Photon Manufacturing Science and Technology, Jiangsu University, Zhenjiang 212013 (China); Ren, Nai-fei [Jiangsu Provincial Key Laboratory of Center for Photon Manufacturing Science and Technology, Jiangsu University, Zhenjiang 212013 (China); School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Kong, Xia; Cai, Yun-long; Zhang, Jie-lu [Jiangsu Tailong Reduction Box Co. Ltd., Taixing 225400 (China)

2015-10-01

Highlights: • Ni/FTO films were prepared by sputtering Ni layers on commercial FTO glass. • The as-prepared Ni/FTO films underwent magnetic-field-assisted laser annealing. • Magnetic field and laser fluence were crucial for improving quality of the films. • All Ni/FTO films displayed enhanced compactness after magnetic laser annealing. • Magnetic laser annealing using a fluence of 0.9 J/cm{sup 2} led to the best film quality. - Abstract: Nickel-coated fluorine-doped tin oxide (Ni/FTO) thin films were prepared by sputtering Ni layers on commercial FTO glass. The as-prepared Ni/FTO films underwent nanosecond pulsed laser annealing in an external magnetic field (0.4 T). The effects of the presence of magnetic field and laser fluence on surface morphology, crystal structure and photoelectric properties of the films were investigated. All the films displayed enhanced compactness after magnetic-field-assisted laser annealing. It was notable that both crystallinity and grain size of the films gradually increased with increasing laser fluence from 0.6 to 0.9 J/cm{sup 2}, and then decreased slightly with an increase in laser fluence to 1.1 J/cm{sup 2}. As a result, the film obtained by magnetic-field-assisted laser annealing using a fluence of 0.9 J/cm{sup 2} had the best overall photoelectric property with an average transmittance of 81.2%, a sheet resistance of 5.5 Ω/sq and a figure of merit of 2.27 × 10{sup −2} Ω{sup −1}, outperforming that of the film obtained by pure laser annealing using the same fluence.

Polycrystalline magnetic garnet films comprising weakly coupled crystallites for piezoelectrically-driven magneto-optic spatial light modulators

Energy Technology Data Exchange (ETDEWEB)

Mito, S.; Sakurai, H.; Takagi, H.; Inoue, M. [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Baryshev, A. V. [Electronics-Inspired Interdisciplinary Research Institute Toyohashi, Aichi 441-8580 (Japan); Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)

2012-04-01

We have investigated the magnetization process of the polycrystalline magnetic garnet films in order to determine the most suitable composition of garnet films for piezoelectrically-driven magneto-optic spatial light modulators (MOSLMs). For experiment, the bismuth-dysprosium-aluminum-substituted yttrium iron (Bi{sub 1.3}Dy{sub 0.7}Y{sub 1.0}Fe{sub 3.1}Al{sub 1.9}O{sub 12}) garnet films were deposited by an RF magnetron sputter and annealed at 700 deg. C in air. The annealing time was varied in a range of several minutes to control the grain size. The saturation magnetization, the remanent magnetization and the composition of the fabricated garnet films slightly changed versus the annealing time. Experiments showed that the coercivity and the grain size increased at longer annealing; the coercivity was larger for films with bigger grains. This work shows that garnet films with smaller coercivity are most suitable for controlling the magnetization of garnet and, correspondingly, the magneto-optical rotation of MOSLM pixels driven by piezoelectrics.

Effect of laser beam parameters on magnetic properties of Nd-Fe-B thick-film magnets fabricated by pulsed laser deposition

International Nuclear Information System (INIS)

Fukunaga, H.; Nakano, M.; Yanai, T.; Kamikawatoko, T.; Yamashita, F.

2011-01-01

The effects of varying the laser power and the spot diameter of a laser beam on the magnetic properties, morphology, and deposition rate of Nd-Fe-B thick-film magnets fabricated by pulsed laser deposition (PLD) were investigated. Reducing the laser fluence on the target reduces the remanence and increases the Nd content and consequently the coercivity of the prepared films. The spot size of the laser beam was found to affect the film surface morphology, the deposition rate, and the reproducibility of the magnetic properties of the prepared films. Reducing the spot size reduces the number of droplets and the reproducibility of the magnetic properties and increases the droplet size. Controlling the spot size of the laser beam enabled us to maximize the deposition rate. Consequently, a coercivity of 1210 kA/m and a remanence of 0.51 T were obtained at a deposition rate of 11.8 μm/(h·W). This deposition rate is 30% greater than the highest previously reported deposition rate by PLD.

Theoretical investigation of electronic, magnetic and optical properties of Fe doped GaN thin films

International Nuclear Information System (INIS)

Salmani, E.; Mounkachi, O.; Ez-Zahraouy, H.; Benyoussef, A.; Hamedoun, M.; Hlil, E.K.

2013-01-01

Highlights: •Magnetic and optical properties Fe-doped GaN thin films are studied using DFT. •The band gaps of GaN thin films are larger than the one of the bulk. •The layer thickness and acceptor defect can switch the magnetic ordering. -- Abstract: Using first principles calculations based on spin-polarized density functional theory, the magnetic and optical properties of GaN and Fe-doped GaN thin films with and without acceptor defect is studied. The band structure calculations show that the band gaps of GaN thin films with 2, 4 and 6 layers are larger than the one of the bulk with wurtzite structure and decreases with increasing the film thickness. In Fe doped GaN thin films, we show that layer of thickness and acceptor defect can switch the magnetic ordering from disorder local moment (DLM) to ferromagnetic (FM) order. Without acceptor defect Fe doped GaN exhibits spin glass phase in 4 layers form and ferromagnetic state for 2 layers form of the thin films, while it exhibits ferromagnetic phase with acceptor defect such as vacancies defect for 2 and 4 layers. In the FM ordering, the thin films is half-metallic and is therefore ideal for spin application. The different energy between ferromagnetic state and disorder local moment state was evaluated. Moreover, the optical absorption spectra obtained by ab initio calculations confirm the ferromagnetic stability based on the charge state of magnetic impurities

Engineering Gilbert damping by dilute Gd doping in soft magnetic Fe thin Films

NARCIS (Netherlands)

Zhang, W.; Jiang, S.; Wong, P.K.J.; Sun, Li; Wang, Y.K.; Wang, Kai; de Jong, Machiel Pieter; van der Wiel, Wilfred Gerard; van der Laan, G.; Zhai, Y.

2014-01-01

By analyzing the ferromagnetic resonance linewidth, we show that the Gilbert damping constant in soft magnetic Fe thin films can be enhanced by ∼6 times with Gd doping of up to 20%. At the same time, the magnetic easy axis remains in the film plane while the coercivity is strongly reduced after Gd

Electronic structure and magnetic properties of Ni-doped SnO2 thin films

Science.gov (United States)

Sharma, Mayuri; Kumar, Shalendra; Alvi, P. A.

2018-05-01

This paper reports the electronic structure and magnetic properties of Ni-doped SnO2 thin film which were grown on Si (100) substrate by PLD (pulse laser deposition) technique under oxygen partial pressure (PO2). For getting electronic structure and magnetic behavior, the films were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DC magnetization measurements. The NEXAFS study at Ni L3,2 edge has been done to understand the local environment of Ni and Sn ions within SnO2 lattice. DC magnetization measurement shows that the saturation magnetization increases with the increase in substitution of Ni2+ ions in the system.

Effect of magnetization boundary condition on cavity magnon polariton of YIG thin film

Science.gov (United States)

Jiang, H. H.; Xiao, Y.; Hu, C. M.; Guo, H.; Xia, K.

2018-06-01

Motivated by recent studies of cavity magnon polariton (CMP), we extended a previous theoretical work to generalize microwave transmission calculation with various magnetization boundary condition of YIG thin film embedded in cavity. It is found that numerical implementation given in this paper can be easily applied to other magnetization boundary condition and extended to magnetic multilayers. Numerical results show that ferromagnetic resonance mode of microwave transmission spectrum, which is absent in previous calculation, can be recovered by altering the pinning condition of surface spins. The demonstrated reliability of our theory opens attractive perspectives for studying CMP of thin film with complicated surface magnetization distribution and magnetic multilayers.

The local structure, magnetic, and transport properties of Cr-doped In2O3 films

International Nuclear Information System (INIS)

Wang Shiqi; An Yukai; Feng Deqiang; Liu Jiwen; Wu Zhonghua

2013-01-01

Cr-doped In 2 O 3 films were deposited on Si (100) substrates by RF-magnetron sputtering technique. The local structure, magnetic, and transport properties of films are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, Hall effect, R-T, and magnetic measurements. Structural analysis clearly indicates that Cr ions substitute for In 3+ sites of the In 2 O 3 lattice in the valence of +2 states and Cr-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. The films with low Cr concentration show a crossover from semiconducting to metallic transport behavior, whereas only semiconducting behavior is observed in high Cr concentration films. The transport property of all films is governed by Mott variable range hopping behavior, suggesting that the carriers are strongly localized. Magnetic characterizations show that the saturated magnetization of films increases first, and then decreases with Cr doping, while carrier concentration n c decreases monotonically, implying that the ferromagnetism is not directly induced by the mediated carriers. It can be concluded the ferromagnetism of films is intrinsic and originates from electrons bound in defect states associated with oxygen vacancies.

Synthesis, nanostructure and magnetic properties of FeCo-reduced graphene oxide composite films by one-step electrodeposition

International Nuclear Information System (INIS)

Cao, Derang; Li, Hao; Wang, Zhenkun; Wei, Jinwu; Wang, Jianbo; Liu, Qingfang

2015-01-01

FeCo-reduced graphene oxide (FeCo-RGO) composite film was fabricated on indium tin oxide substrate using one-step electrodeposition method. Raman spectroscopy and field emission scanning electron microscope results show that the reduced graphene oxide is coprecipitated with the FeCo film. The energy-dispersive spectrometer results demonstrate that the atomic ratio of Fe/Co in FeCo-RGO composite film is larger than that of the FeCo film under the same fabrication condition. As a result, the FeCo-RGO composite film exhibits good soft magnetic properties and high-frequency properties as well as the FeCo film. The magnetic anisotropy field and saturation magnetization of FeCo-RGO composite film are increased when compared with FeCo film. Furthermore, the ferromagnetic resonance frequency is improved from 2.15 GHz for the FeCo film to 3.9 GHz for the FeCo-RGO composite film. - Highlights: • FeCo-reduced graphene oxide composite film was fabricated on indium tin oxide substrate. • One step electrodeposition method was used. • Good soft magnetic properties were exhibited by the composite films. • Increase of resonance frequency from 2.15 GHz for FeCo film to 3.9 GHz for composite film

Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Sokolov, N. S., E-mail: nsokolov@fl.ioffe.ru; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V. [Ioffe Physical-Technical Institute of Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Maksimova, K. Yu.; Grunin, A. I. [Immanuel Kant Baltic Federal University, Kaliningrad 236041 (Russian Federation); Tabuchi, M. [Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603 (Japan)

2016-01-14

Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

International Nuclear Information System (INIS)

Sokolov, N. S.; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V.; Maksimova, K. Yu.; Grunin, A. I.; Tabuchi, M.

2016-01-01

Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y 3 Fe 5 O 12 (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films

Tunable Snell's law for spin waves in heterochiral magnetic films

Science.gov (United States)

Mulkers, Jeroen; Van Waeyenberge, Bartel; Milošević, Milorad V.

2018-03-01

Thin ferromagnetic films with an interfacially induced DMI exhibit nontrivial asymmetric dispersion relations that lead to unique and useful magnonic properties. Here we derive an analytical expression for the magnon propagation angle within the micromagnetic framework and show how the dispersion relation can be approximated with a comprehensible geometrical interpretation in the k space of the propagation of spin waves. We further explore the refraction of spin waves at DMI interfaces in heterochiral magnetic films, after deriving a generalized Snell's law tunable by an in-plane magnetic field, that yields analytical expressions for critical incident angles. The found asymmetric Brewster angles at interfaces of regions with different DMI strengths, adjustable by magnetic field, support the conclusion that heterochiral ferromagnetic structures are an ideal platform for versatile spin-wave guides.

Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

Science.gov (United States)

Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

2018-04-25

In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

Integrated magnetic transformer assembly

DEFF Research Database (Denmark)

2014-01-01

The present invention relates to an integrated magnetics transformer assembly comprising a first magnetically permeable core forming a first substantially closed magnetic flux path and a second magnetically permeable core forming a second substantially closed magnetic flux path. A first input...... inductor winding is wound around a first predetermined segment of the first magnetically permeable core and a second input inductor winding is wound around a first predetermined segment of the second magnetically permeable core. The integrated magnetics transformer assembly further comprises a first output......-winding of the first output inductor winding and the first half-winding of the second output inductor winding are configured to produce aligned, i.e. in the same direction, magnetic fluxes through the first substantially closed magnetic flux path. The integrated magnetics transformer assembly is well- suited for use...

Spontaneous magnetization of thin films of ordered and disordered alloys of transition metals

International Nuclear Information System (INIS)

Nguyen Nhat Khanh.

1989-12-01

A method of calculation of spontaneous magnetization of thin films of transition metal alloys is described. The method is based on the Hubbard model for d electrons. Use of the Bragg-Williams approximation and two-dimensional canonical transformations has allowed to calculate the magnetization. Results for a Ni 3 Fe thin film are presented. (author). 11 refs, 1 fig

Magnetic properties changes of MnAs thin films irradiated with highly charged ions

OpenAIRE

Trassinelli , Martino; Gafton , V.; Eddrief , Mahmoud; Etgens , Victor H.; Hidki , S.; Lacaze , Emmanuelle; Lamour , Emily; Luo , X.; Marangolo , Massimiliano; Merot , Jacques; Prigent , Christophe; Reuschl , Regina; Rozet , Jean-Pierre; Steydli , S.; Vernhet , Dominique

2013-01-01

International audience; We present the first investigation on the effect of highly charged ion bombardment on a manganese arsenide thin film. The MnAs films, 150~nm thick, are irradiated with 90 keV Ne$^{9+}$ ions with a dose varying from $1.6\\times10^{12}$ to $1.6\\times10^{15}$~ions/cm$^2$. The structural and magnetic properties of the film after irradiation are investigated using different techniques, namely, X-ray diffraction, magneto-optic Kerr effect and magnetic force microscope. Prelim...

Local imaging of magnetic flux in superconducting thin films

International Nuclear Information System (INIS)

Shapoval, Tetyana

2010-01-01

Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-μm-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa 2 Cu 3 O 7-δ thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)

Structural, mechanical, and magnetic properties of GaFe_3N thin films

International Nuclear Information System (INIS)

Junaid, Muhammad; Music, Denis; Hans, Marcus; Schneider, Jochen M.; Scholz, Tanja; Dronskowski, Richard; Primetzhofer, Daniel

2016-01-01

Using the density-functional theory, the structural, mechanical, and magnetic properties were investigated for different GaFe_3N configurations: ferromagnetic, ferrimagnetic, paramagnetic, and nonmagnetic. Ferrimagnetic and high-spin ferromagnetic states exhibit the lowest energy and are the competing ground states as the total energy difference is 0.3 meV/atom only. All theoretically predicted values could be fully confirmed by experiments. For this, the authors synthesized phase pure, homogeneous, and continuous GaFe_3N films by combinatorial reactive direct current magnetron sputtering. Despite the low melting point of gallium, the authors succeeded in the growth of GaFe_3N films at a temperature of 500 °C. Those thin films exhibit a lattice parameter of 3.794 Å and an elastic modulus of 226 ± 20 GPa. Magnetic susceptibility measurements evidence a magnetic phase transitions at 8.0 ± 0.1 K. The nearly saturated magnetic moment at ±5 T is about 1.6 μB/Fe and is close to the theoretically determined magnetic moment for a ferrimagnetic ordering (1.72 μB/Fe).

Methods for Probing Magnetic Films with Neutrons

Science.gov (United States)

Kozhevnikov, S. V.; Ott, F.; Radu, F.

2018-03-01

We review various methods in the investigation of magnetic films with neutrons, including those based on the effects of Larmor precession, Zeeman spatial splitting of the beam, neutron spin resonance, and polarized neutron channeling. The underlying principles, examples of the investigated systems, specific features, applications, and perspectives of these methods are discussed.

Three dimensional simulation of giant magneto-impedance effect in thin film structures

KAUST Repository

Li, Bodong; Kosel, Jü rgen

2011-01-01

In this paper, a three dimensional model for the giant magneto-impedance (GMI) effect in thin film structures is developed using the finite element method(FEM) with a GMI permeability model embedded. One-layer, three-layer, and five-layer thin film structures are simulated. The GMI effect and the sensitivity are calculated as a function of the external magnetic field, driving frequency, and the thickness of the magnetic layers. The results show that the five-layer structure has the best performance, which is in accordance with experimental results. The GMI ratio and the sensitivity first improve with the increasing thickness of the magnetic layer but reach saturation at a certain value of the thickness. In a five-layer structure,saturation of the GMI effect becomes effective at about 3 μm thickness of the magnetic layers, where a GMI ratio of 1125% was obtained, with a corresponding sensitivity of 0.37%/A/m (29.6%/Oe).

Three dimensional simulation of giant magneto-impedance effect in thin film structures

KAUST Repository

Li, Bodong

2011-04-04

In this paper, a three dimensional model for the giant magneto-impedance (GMI) effect in thin film structures is developed using the finite element method(FEM) with a GMI permeability model embedded. One-layer, three-layer, and five-layer thin film structures are simulated. The GMI effect and the sensitivity are calculated as a function of the external magnetic field, driving frequency, and the thickness of the magnetic layers. The results show that the five-layer structure has the best performance, which is in accordance with experimental results. The GMI ratio and the sensitivity first improve with the increasing thickness of the magnetic layer but reach saturation at a certain value of the thickness. In a five-layer structure,saturation of the GMI effect becomes effective at about 3 μm thickness of the magnetic layers, where a GMI ratio of 1125% was obtained, with a corresponding sensitivity of 0.37%/A/m (29.6%/Oe).

Growth and magnetic properties of multiferroic LaxBi1-xMnO3 thin films

Science.gov (United States)

Gajek, M.; Bibes, M.; Wyczisk, F.; Varela, M.; Fontcuberta, J.; Barthélémy, A.

2007-05-01

A comparative study of LaxBi1-xMnO3 thin films grown on SrTiO3 substrates is reported. It is shown that these films grow epitaxially in a narrow pressure-temperature range. A detailed structural and compositional characterization of the films is performed within the growth window. The structure and the magnetization of this system are investigated. We find a clear correlation between the magnetization and the unit-cell volume that we ascribe to Bi deficiency and the resultant introduction of a mixed valence on the Mn ions. On these grounds, we show that the reduced magnetization of LaxBi1-xMnO3 thin films compared to the bulk can be explained quantitatively by a simple model, taking into account the deviation from nominal composition and the Goodenough-Kanamori-Anderson rules of magnetic interactions.

Collision-Free Structure Using Thin-Film Magnet For Electrostatic Energy Harvester

International Nuclear Information System (INIS)

Yoshii, S; Yamaguchi, K; Fujita, T; Kanda, K; Maenaka, K

2016-01-01

This paper proposes collision-free structure using NdFeB thin-film magnet for vibration energy harvesters. By using stripe shaped NdFeB magnet array on the Si MEMS structure, we finally obtained 3 mN of magnetic repulsive force on 8 × 8 mm 2 specimen with 40 μm air-gap. (paper)

Collision-Free Structure Using Thin-Film Magnet For Electrostatic Energy Harvester

Science.gov (United States)

Yoshii, S.; Yamaguchi, K.; Fujita, T.; Kanda, K.; Maenaka, K.

2016-11-01

This paper proposes collision-free structure using NdFeB thin-film magnet for vibration energy harvesters. By using stripe shaped NdFeB magnet array on the Si MEMS structure, we finally obtained 3 mN of magnetic repulsive force on 8 × 8 mm2 specimen with 40 μm air-gap.

Enhanced magnetic properties of chemical solution deposited BiFeO3 thin film with ZnO buffer layer

International Nuclear Information System (INIS)

Rajalakshmi, R.; Kambhala, Nagaiah; Angappane, S.

2012-01-01

Highlights: ► Enhanced magnetization of BiFeO 3 is important for strong magnetoelectric coupling. ► BiFeO 3 film with ZnO buffer layer was successfully synthesized by chemical method. ► Magnetization of BiFeO 3 has increased by more than 10 times with ZnO buffer layer. ► A mechanism for enhancement in ferromagnetism of BiFeO 3 film is proposed. - Abstract: Magnetic properties of BiFeO 3 films deposited on Si substrates with and without ZnO buffer layer have been studied in this work. We adopted the chemical solution deposition method for the deposition of BiFeO 3 as well as ZnO films. The x-ray diffraction measurements on the deposited films confirm the formation of crystalline phase of BiFeO 3 and ZnO films, while our electron microscopy measurements help to understand the morphology of few micrometers thick films. It is found that the deposited ZnO film exhibit a hexagonal particulate surface morphology, whereas BiFeO 3 film fully covers the ZnO surface. Our magnetic measurements reveal that the magnetization of BiFeO 3 has increased by more than ten times in BiFeO 3 /ZnO/Si film compared to BiFeO 3 /Si film, indicating the major role played by ZnO buffer layer in enhancing the magnetic properties of BiFeO 3 , a technologically important multiferroic material.

Superconducting Film Flux Transformer for a Sensor of a Weak Magnetic Field

International Nuclear Information System (INIS)

Ichkitidze, L; Mironyuk, A

2012-01-01

The object of study is a superconducting film flux transformer in the form of a square shaped loop with the tapering operative strip used in a sensor of a weak magnetic field. The magnetosensitive film element based on the giant magnetoresistance effect is overlapped with the tapering operative strip of the flux transformer; it is separated from the latter by the insulator film. It is shown that the topological nanostructuring of the operative strip of the flux transformer increases its gain factor by one or more orders of magnitude, i.e. increases its efficiency, which leads to a significant improvement of important parameters of a magnetic-field sensor.

Antidot patterned single and bilayer thin films based on ferrimagnetic Tb-Co alloy with perpendicular magnetic anisotropy

Science.gov (United States)

Kulesh, N. A.; Vázquez, M.; Lepalovskij, V. N.; Vas'kovskiy, V. O.

2018-02-01

Hysteresis properties and magnetization reversal in TbCo(30 nm) and FeNi(10 nm)/TbCo(30 nm) films with nanoscale antidot lattices are investigated to test the effect of nanoholes on the perpendicular anisotropy in the TbCo layer and the induced exchange bias in the FeNi layer. The antidots are introduced by depositing the films on top of hexagonally ordered porous anodic alumina substrates with pore diameter and interpore distance fixed to 75 nm and 105 nm, respectively. The analysis of combined vibrating sample magnetometry, Kerr microscopy and magnetic force microscopy imaging measurements has allowed us to link macroscopic and local magnetization reversal processes. For magnetically hard TbCo films, we demonstrate the tunability of magnetic anisotropy and coercive field (i.e., it increases from 0.2 T for the continuous film to 0.5 T for the antidot film). For the antidot FeNi/TbCo film, magnetization of FeNi is confirmed to be in plane. Although an exchange bias has been locally detected in the FeNi layer, the integrated hysteresis loop has increased coercivity and zero shift along the field axis due to the significantly decreased magnetic anisotropy of TbCo layer.

Effect of tungsten (W) on structural and magnetic properties of electroplated NiFe thin films for MEMS applications

Science.gov (United States)

Kannan, R.; Devaki, P.; Premkumar, P. S.; Selvambikai, M.

2018-04-01

Electrodeposition of nanocrystalline NiFe and NiFeW thin films were carried out from ammonium citrate bath at a constant current density and controlled pH of 8 by varying the bath temperature from 40 °C to 70 °C. The surface morphology and chemical composition of the electrodeposited NiFe and NiFeW soft magnetic thin films were studied by using SEM and EDAX. The SEM micrographs of the films coated at higher electrodeposited bath temperature have no micro cracks and also the films have more uniform surface morphology. The existence of crystalline nature of the coated films were analysed by XRD. The presence of predominant peaks in x-ray diffraction pattern (compared with JCPDS data) reveal that the average crystalline size was in the order of few tens of nano meters. The magnetic properties such as coercivity, saturation magnetization and magnetic flux density have been calculated from vibrating sample magnetometer analysis. The VSM result shows that the NiFeW thin film synthesised at 70 °C exhibit the lower coercivity with higher saturation magnetization. The hardness and adhesion of the electroplated films have been investigated. Reasons for variation in magnetic properties and structural characteristics are also discussed. The electroplated NiFe and NiFeW thin films can be used for Micro Electro Mechanical System (MEMS) applications due to their excellent soft magnetic behaviour.

Magnetic Properties of Fe(001) Thin Films on GaAs(001) Deposited by RF Magnetron Sputtering

International Nuclear Information System (INIS)

Ikeya, Hirokazu; Takahashi, Yutaka; Inaba, Nobuyuki; Kirino, Fumiyoshi; Ohtake, Mitsuru; Futamoto, Masaaki

2011-01-01

Fe thin films, down to 6 nm thick, were prepared on GaAs(001) substrates by RF magnetron sputtering. The x-ray diffraction (XRD) analyses show that the epitaxial thin films of Fe(001) were grown with cube-on-cube orientation on GaAs(001). Magnetic properties were investigated by vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) spectroscopy. The magnetization curves obtained by applying in-plane magnetic fields indicate that easy (hard) direction is along [100] ([110]) and the saturation magnetization is close to the bulk values. The in-plane magnetic anisotropy measured by FMR shows four-fold symmetry, as expected for bcc Fe. We did not observe the in-plane uniaxial magnetic anisotropy reported on the MBE-grown Fe films on GaAs substrates.

High Temperature Magnetic Properties of Indirect Exchange Spring FePt/M(Cu,C/Fe Trilayer Thin Films

Directory of Open Access Journals (Sweden)

Anabil Gayen

2013-01-01

Full Text Available We report the investigation of temperature dependent magnetic properties of FePt and FePt(30/M(Cu,C/Fe(5 trilayer thin films prepared by using magnetron sputtering technique at ambient temperature and postannealed at different temperatures. L10 ordering, hard magnetic properties, and thermal stability of FePt films are improved with increasing postannealing temperature. In FePt/M/Fe trilayer, the formation of interlayer exchange coupling between magnetic layers depends on interlayer materials and interface morphology. In FePt/C/Fe trilayer, when the C interlayer thickness was about 0.5 nm, a strong interlayer exchange coupling between hard and soft layers was achieved, and saturation magnetization was enhanced considerably after using interlayer exchange coupling with Fe. In addition, incoherent magnetization reversal process observed in FePt/Fe films changes into coherent switching process in FePt/C/Fe films giving rise to a single hysteresis loop. High temperature magnetic studies up to 573 K reveal that the effective reduction in the coercivity decreases largely from 34 Oe/K for FePt/Fe film to 13 Oe/K for FePt/C(0.5/Fe film demonstrating that the interlayer exchange coupling seems to be a promising approach to improve the stability of hard magnetic properties at high temperatures, which is suitable for high-performance magnets and thermally assisted magnetic recording media.

Influence of stresses and magnetostriction on the soft magnetic behavior of metallic films

NARCIS (Netherlands)

Chezan, AR; Craus, CB; Chechenin, NG; Vystavel, T; Niesen, L; De Hosson, JTM; Boerma, DO

Nanocrystalline soft magnetic Fe-Zr-N films have been successfully deposited by DC magnetron reactive sputtering. For thick films (>200 nm), the compressive stress in the as-deposited films and the positive matgnetostriction produce perpendicular anisotropy. The magnitude of this effect is smaller

Magnetic and exchange bias properties of YCo thin films and IrMn/YCo bilayers

Science.gov (United States)

Venkat Narayana, M.; Manivel Raja, M.; Jammalamadaka, S. Narayana

2018-02-01

We report on the structural and magnetic properties of YCo thin films and IrMn/YCo bilayers. X-ray diffraction infer that all the films are amorphous in nature. Magnetization versus magnetic field measurements reveal room temperature soft ferromagnetism in all the YCo films. Thin films which were grown at 100 W sputter power with growth rates of 0.677, 0.694 and 0.711 Å/sec show better morphology and composition than 50 W (0.333, 0.444 and 0.277 Å/sec) grown films. Perpendicular exchange bias in as deposited bilayers is evident for IrMn/YCo bilayers. Exchange bias (EB) decreases in case of in plane measurements and enhances for out of plane measurements after perpendicular field annealing. EB is more in case of out of plane direction due to large perpendicular anisotropy in comparison with in plane direction. Above the critical thickness, EB variation is explained on the basis of random field model in the Heisenberg regime, which has been proposed by Malozemoff. Indeed there exists an inverse relationship between EB and IrMn layer thickness. Evidenced vertical shift apart from the horizontal shift for magnetization loops is attributed to frozen magnetic moments in one of the layers at the interface. Present results would prove to be helpful in spintronic device applications.

Magnetic and structural studies on nanostructured Gd/Cr multilayer films

International Nuclear Information System (INIS)

Gadioli, G.Z.; Rouxinol, F.P.; Gelamo, R.V.; Cardoso, L.P.; Gama, S.; Bica de Moraes, M.A.

2013-01-01

Investigations of magnetic phases, transition temperatures and coercivity were performed in multilayered Gd/Cr films as a function of the crystalline state and morphology of the Gd layers. The films were deposited by dc magnetron sputtering at three substrate temperatures, T s , (room temperature, 300 and 500 °C). The Gd and Cr thicknesses were of 10 and 30 nm, respectively. Two series of three films were prepared. In one of the series, the films had a single Gd/Cr bilayer; in the other, 15 bilayers. The discontinuous or granular nature of the Gd layers was revealed by scanning electron microscopy Grazing incidence angle x-ray diffraction was used to investigate the crystalline state of the Gd and Cr layers. These techniques revealed that grain average size and crystalline order increase with increasing T s . From dc magnetic measurements, the co-existence of ferromagnetic and superferromagnetic phases in the Gd layers was observed, and Curie transition temperatures, T C , were determined. High coercive fields at low temperature (2 K) were measured in hysteresis cycles. Field-cooled and zero field-cooled magnetizations as functions of temperature curves exhibited, for some of the samples, a low temperature peak suggesting a freezing transition to a cluster glass state. This was confirmed by complementary ac-susceptibility measurements carried out as a function of temperature, for various frequencies of the ac field. Some results of this work – the decline in T C for decreasing Gd grain size, the high coercive field and its dependence on particle size, and the behavior of the magnetization at low temperatures for the sample deposited at room temperature – are discussed in terms of finite size and surface effects in nanosized particles. - Highlights: • Sputter-deposited Gd/Cr multilayer films with nanostructured Gd layers • Ferromagnetic and superferromagnetic phases are observed. • Ferromagnetic phase dependent of the deposition temperature • Improved

Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

Science.gov (United States)

Fujiwara, Ryogen; Devillers, Thibaut; Givord, Dominique; Dempsey, Nora M.

2018-05-01

Hard magnetic films used in magnetic micro-systems may be exposed to elevated temperatures during film and system fabrication and also during use of the micro-system. In this work, we studied the influence of temperature on the magnetic properties of 10 μm thick out-of-plane textured NdFeB films fabricated by high rate triode sputtering. Out-of-plane hysteresis loops were measured in the range 300K - 650K to establish the temperature dependence of coercivity, magnetization at 7 T and remanent magnetization. Thermal demagnetization was measured and magnetization losses were recorded from 350K in films heated under zero or low (-0.1 T) external field and from 325 K for films heated under an external field of -0.5 T. The effect of thermal cycling under zero field on the remanent magnetization was also studied and it was found that cycling between room temperature and 323 K did not lead to any significant loss in remanence at room temperature, while a 4% drop is recorded when the sample is cycled between RT and 343K. Measurement of hysteresis loops at room temperature following exposure to elevated temperatures reveals that while remanent magnetisation is practically recovered in all cases, irreversible losses in coercivity occur (6.7 % following heating to 650K, and 1.3 % following heating to 343K). The relevance of these results is discussed in terms of system fabrication and use.

Modelling the effects of porous and semi-permeable layers on corrosion processes

International Nuclear Information System (INIS)

King, F.; Kolar, M.; Shoesmith, D.W.

1996-09-01

Porous and semi-permeable layers play a role in many corrosion processes. Porous layers may simply affect the rate of corrosion by affecting the rate of mass transport of reactants and products to and from the corroding surface. Semi-permeable layers can further affect the corrosion process by reacting with products and/or reactants. Reactions in semi-permeable layers include redox processes involving electron transfer, adsorption, ion-exchange and complexation reactions and precipitation/dissolution processes. Examples of porous and semi-permeable layers include non-reactive salt films, precipitate layers consisting of redox-active species in multiple oxidation states (e.g., Fe oxide films), clay and soil layers and biofilms. Examples of these various types of processes will be discussed and modelling techniques developed from studies for the disposal of high-level nuclear waste presented. (author). 48 refs., 1 tab., 12 figs

CoPt/TiN films nanopatterned by RF plasma etching towards dot-patterned magnetic media

Science.gov (United States)

Szívós, János; Pothorszky, Szilárd; Soltys, Jan; Serényi, Miklós; An, Hongyu; Gao, Tenghua; Deák, András; Shi, Ji; Sáfrán, György

2018-03-01

CoPt thin films as possible candidates for Bit Patterned magnetic Media (BPM) were prepared and investigated by electron microscopy techniques and magnetic measurements. The structure and morphology of the Direct Current (DC) sputtered films with N incorporation were revealed in both as-prepared and annealed state. Nanopatterning of the samples was carried out by means of Radio Frequency (RF) plasma etching through a Langmuir-Blodgett film of silica nanospheres that is a fast and high throughput technique. As a result, the samples with hexagonally arranged 100 nm size separated dots of fct-phase CoPt were obtained. The influence of the order of nanopatterning and anneling on the nanostructure formation was revealed. The magnetic properties of the nanopatterned fct CoPt films were investigated by Vibrating Sample Magnetometer (VSM) and Magnetic Force Microscopy (MFM). The results show that CoPt thin film nanopatterned by means of the RF plasma etching technique is promising candidate to a possible realization of BPM. Furthermore, this technique is versatile and suitable for scaling up to technological and industrial applications.

Polarization enhancement and ferroelectric switching enabled by interacting magnetic structures in DyMnO3 thin films

KAUST Repository

Lu, Chengliang

2013-12-02

The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the corresponding thin films remains an unresolved issue, which unfortunately halts this step. In this work, we report magnetically induced electric polarization and its remarkable response to magnetic field (an enhancement of ?800% upon a field of 2 Tesla at 2 K) in DyMnO3 thin films grown on Nb-SrTiO3 substrates. Accompanying with the large polarization enhancement, the ferroelectric coercivity corresponding to the magnetic chirality switching field is significantly increased. A picture based on coupled multicomponent magnetic structures is proposed to understand these features. Moreover, different magnetic anisotropy related to strain-suppressed GdFeO 3-type distortion and Jahn-Teller effect is identified in the films.

Local imaging of magnetic flux in superconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Shapoval, Tetyana

2010-01-26

Local studies of magnetic flux line (vortex) distribution in superconducting thin films and their pinning by natural and artificial defects have been performed using low-temperature magnetic force microscopy (LT-MFM). Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural defects under the influence of the force that the MFM tip exerts on the individual vortex was visualized and the local pinning force was estimated. The good agreement of these results with global transport measurements demonstrates that MFM is a powerful and reliable method to probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the presence of an ordered array of 1-{mu}m-sized ferromagnetic permalloy dots being in a magneticvortex state underneath the Nb film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the superconducting vortices and allows vortex clusters to be located at each dot. Additionally, for industrially applicable YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films the main question discussed was the possibility of a direct correlation between vortices and artificial defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness (droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge polishing technique that allows to overcome this problem was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample. It provides a continuous insight from the film surface down to the substrate with surface sensitive scanning techniques. (orig.)

Effects of deposition temperature and in-situ annealing time on structure and magnetic properties of (001) orientation FePt films

International Nuclear Information System (INIS)

Yu, Yongsheng; George, T.A.; Li, Haibo; Sun, Daqian; Ren, Zhenan; Sellmyer, D.J.

2013-01-01

FePt films were prepared on (100) oriented single crystal MgO substrates at high temperature ranging from 620 until 800 °C and in-situ annealed for different times ranging from 0 to 60 min to obtain ordered FePt films. The structural analysis indicates that FePt films grow epitaxially on MgO (100) substrates. Both increasing deposition temperature and in-situ annealing time enhance the (001) texture and ordering of FePt films. The magnetic analysis shows that these L1 0 FePt films have perpendicular anisotropy and the easy magnetization c-axis is perpendicular to the film plane. Magnetization reversal is controlled by a rotational mechanism. The hard magnetic properties of the films are improved with increasing deposition temperature or in-situ annealing time. - Highlights: ► The paper reports the texture and magnetic evolution of FePt films deposited on MgO substrates. ► Increasing deposition temperature or annealing time enhanced the texture and ordering. ► The magnetic analysis shows L1 0 FePt films have perpendicular anisotropy.

Structural and magnetic anisotropy in the epitaxial FeV2O4 (110) spinel thin films

Science.gov (United States)

Shi, Xiaolan; Wang, Yuhang; Zhao, Kehan; Liu, Na; Sun, Gaofeng; Zhang, Liuwan

2015-11-01

The epitaxial 200-nm-thick FeV2O4(110) films on (110)-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

Temperature-induced transitions between domain structures of ultrathin magnetic films

International Nuclear Information System (INIS)

Polyakova, T.; Zablotskii, V.

2005-01-01

Full text: Understanding of the influence of temperature on behavior of domain patterns of ultrathin magnetic films is of high significance for the fundamental physics of nanomagnetism as well as for technological applications. A thickness-dependent Curie temperature of ultrathin films may cause many interesting phenomena in the thermal evolution of domain structures (DS): i) nontrivial changes of the anisotropy constants as a function of the film thickness; ii) so-called inverse melting of DSs (processes where a more symmetric domain phase is found at lower temperatures than at higher temperatures - the inverse phase sequence) [1]; iii) temperature-induced transitions between domain structures. The possibility of such transitions is determined by lowering of the potential barriers separating different magnetization states as the film temperature approaches the Curie point. In this case with an increase of temperature, due to a significant decrease of the anisotropy constant, the domain wall energy is low enough and allows the system to reach equilibrium by a change of the domain wall number in the sample. This manifests itself in a transition from a metastable DS to a more stable DS which corresponds to new values of the anisotropy constant and magnetizations saturation. Thus, the temperature-induced transitions are driven by temperature changes of the magnetic parameters of the film. The key parameters controlling the DS geometry and period are the characteristic length, l c =σ/4πM S 2 (the ratio between the domain wall and demagnetization energies), and the quality factor Q =K/2πM S 2 (K is the first anisotropy constant). We show that for films with a pronounced nonmonotonic temperature dependence of l c one can expect a counter thermodynamic behavior: the inverse phase sequence and cooling-induced disordering. On changing temperature the existing domain structure should accommodate itself under new magnitudes of l c and Q. There are the two possible

Magnetic and structural study of Cu-doped TiO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Torres, C.E. Rodriguez [Dpto de Fisica-IFLP, Fac. Cs. Exactas, Universidad Nacional de La Plata-CONICET, CC 67, 1900 La Plata (Argentina)], E-mail: torres@fisica.unlp.edu.ar; Golmar, F. [Laboratorio de Ablacion Laser, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina); Cabrera, A.F.; Errico, L.; Navarro, A.M. Mudarra; Renteria, M.; Sanchez, F.H. [Dpto de Fisica-IFLP, Fac. Cs. Exactas, Universidad Nacional de La Plata-CONICET, CC 67, 1900 La Plata (Argentina); Duhalde, S. [Laboratorio de Ablacion Laser, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, 1063 Buenos Aires (Argentina)

2007-10-31

Transparent pure and Cu-doped (2.5, 5 and 10 at.%) anatase TiO{sub 2} thin films were grown by pulsed laser deposition technique on LaAlO{sub 3} substrates. The samples were structurally characterized by X-ray absorption spectroscopy and X-ray diffraction. The magnetic properties were measured using a SQUID. All films have a FM-like behaviour. In the case of the Cu-doped samples, the magnetic cycles are almost independent of the Cu concentration. Cu atoms are forming CuO and/or substituting Ti in TiO{sub 2}. The thermal treatment in air promotes the CuO segregation. Since CuO is antiferromagnetic, the magnetic signals present in the films could be assigned to Cu substitutionally replacing cations in TiO{sub 2}.

Magnetic and structural properties of ion beam sputtered Fe–Zr–Nb–B–Cu thin films

International Nuclear Information System (INIS)

Modak, S.S.; Kane, S.N.; Gupta, A.; Mazaleyrat, F.; LoBue, M.; Coisson, M.; Celegato, F.; Tiberto, P.; Vinai, F.

2012-01-01

Magnetic and structural properties of Fe–Zr–Nb–B–Cu thin films, prepared by ion beam sputtering on silicon substrates by using a target made up of amorphous ribbons of nominal composition Fe 84 Zr 3.5 Nb 3.5 B 8 Cu 1 , are reported. As-deposited thin film samples exhibit an in-plane uniaxial anisotropy, which can be ascribed to the preparation technique and the coupling of quenched-in internal stresses. Structural measurements indicate no significant variation of the grain size with thickness and with the annealing temperature. Increase in surface irregularities with annealing temperature and oxidation results in aggregates that would act as pinning centers, affecting the magnetic properties leading to magnetic hardening of the specimens. The role of the magnetic anisotropy is thoroughly discussed with the help of magnetic and ferromagnetic resonance measurements. - Highlights: ►Ion beam sputtered Fe–Zr–Nb–B–Cu thin films of different thickness are prepared. ►Films exhibit in-plane uniaxial anisotropy, which reduces with thermal treatments. ►Increased surface roughness leads to wall pinning, increasing the coercive field.

Basic mode of nonlinear spin-wave resonance in normally magnetized ferrite films