Effect of Mn addition on the structural and magnetic properties of Fe-Pd ferromagnetic shape memory alloys

International Nuclear Information System (INIS)

Sanchez-Alarcos, V.; Recarte, V.; Perez-Landazabal, J.I.; Gonzalez, M.A.; Rodriguez-Velamazan, J.A.

2009-01-01

The effect of Mn addition on the structural and magnetic properties of Fe-Pd ferromagnetic shape memory alloys is investigated. In particular, a complete characterization of the influence of the partial substitution of Fe by Mn has been performed on Fe 69.4-x Pd 30.6 Mn x (x = 0, 1, 2.5 and 5) alloys. The substitution of 1% Fe by Mn fully inhibits the undesirable irreversible face-centered tetragonal to body-centered tetragonal transformation without decreasing the face-centered cubic to face-centered tetragonal temperature. In addition, the substitution of 2.5% Fe by Mn gives rise to the highest thermoelastic transformation temperature observed to date in the Fe-Pd system, probably due to an increase in the valence electron concentration. The magnetocaloric effect has been evaluated in this alloy system for the first time. Nevertheless, the low values obtained suggest that the Fe-Pd alloys are not good candidates for magnetic refrigeration applications.

Synthesis, characterization and catalytic activity of CoFe{sub 2}O{sub 4}-APTES-Pd magnetic recyclable catalyst

Energy Technology Data Exchange (ETDEWEB)

Demirelli, M. [Department of Chemistry, Faculty of Arts and Sciences, Yıldız Teknik University Davutpaşa Campus, Esenler, İstanbul (Turkey); Department of Chemistry, Faculty of Arts and Sciences, Fatih University, B. Cekmece, İstanbul 34500 (Turkey); Karaoğlu, E., E-mail: ebubekirkaraoglu@gmail.com [Department of Chemistry, Faculty of Arts and Sciences, Fatih University, B. Cekmece, İstanbul 34500 (Turkey); Department of Medical Biochemistry, Faculty of Medicine, Sakarya University, Korucuk, Sakarya (Turkey); Baykal, A. [Department of Chemistry, Faculty of Arts and Sciences, Fatih University, B. Cekmece, İstanbul 34500 (Turkey); Sözeri, H.; Uysal, E. [TUBITAK-UME, National Metrology Institute, PO Box 54, 41470 Gebze, Kocaeli (Turkey)

2014-01-05

Highlights: • CoFe{sub 2}O{sub 4}-APTES-Pd (0) nanocomposite, as effective catalysts for reduction reactions. • It could be reused several times without significant loss in hydrogenation reaction. • So far, CoFe{sub 2}O{sub 4}-APTES-Pd (0) nanocomposite have not been synthesized. • CoFe{sub 2}O{sub 4}-APTES-Pd (0) nanocomposite was confirmed by XRD, FT-IR. • Pd containing nanoparticles embedded in organic surfactant observed by TEM. -- Abstract: A new magnetically recyclable catalyst, CoFe{sub 2}O{sub 4}-APTES-Pd(0) nanocomposite, as highly effective catalysts for reduction reactions in liquid phase was fabricated and characterized. The reduction of Pd{sup 2+} was accomplished with sodium borohydride (NaBH{sub 4}). The chemical characterization of the product was done with X-ray diffractometry, infrared spectroscopy, transmission electron microscopy, UV–Vis spectroscopy and inductively coupled plasma. It was found that the combination of CoFe{sub 2}O{sub 4} and 3-aminopropyltriethoxysilane (APTES) could give rise to structurally stable catalytic sites. Furthermore, the high magnetization CoFe{sub 2}O{sub 4}-APTES-Pd(0) catalyst can be recovered by magnet and reused for ten runs for hydrogenation reaction of 4-nitro aniline, 1,3 dinitro and cyclohexanone. The catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least 10 times without significant degradation in the activity which shows the indicative of a potential applications of these catalysts in industry.

structural and magnetic properties of Fe(20Å /Ag(xÅ/Fe(20Å hetro-multilayers

Directory of Open Access Journals (Sweden)

P Ghahramaninezhad

2015-07-01

Full Text Available We have deposited Fe/Ag/Fe multilayer by physical vapor deposition (PVDmethod in different Ag thickness as spacer working in a vacuum of 2×10-6mbar. The structural properties , magnetic response of the samples at low temperatures and room temperature was investigated by XRD, physical properties measurement system (PPMS and vibrating sample magnetometer (VSM respectively. Hysteresis loops show that the easy axis of magnetization is in plane of the film . Also the magnetization and Hc of samples decrease with increasing temperature.

Perpendicular magnetic tunnel junction with thin CoFeB/Ta/Co/Pd/Co reference layer

Energy Technology Data Exchange (ETDEWEB)

Gan, Huadong, E-mail: huadong@avalanche-technology.com; Malmhall, Roger; Wang, Zihui; Yen, Bing K; Zhang, Jing; Wang, Xiaobin; Zhou, Yuchen; Hao, Xiaojie; Jung, Dongha; Satoh, Kimihiro; Huai, Yiming [Avalanche Technology, 46600 Landing Parkway, Fremont, California 94538 (United States)

2014-11-10

Integration of high density spin transfer torque magnetoresistance random access memory requires a thin stack (less than 15 nm) of perpendicular magnetic tunnel junction (p-MTJ). We propose an innovative approach to solve this challenging problem by reducing the thickness and/or moment of the reference layer. A thin reference layer structure of CoFeB/Ta/Co/Pd/Co has 60% magnetic moment of the conventional thick structure including [Co/Pd] multilayers. We demonstrate that the perpendicular magnetization of the CoFeB/Ta/Co/Pd/Co structure can be realized by anti-ferromagnetically coupling to a pinned layer with strong perpendicular anisotropy via Ruderman-Kittel-Kasuya-Yosida exchange interaction. The pMTJ with thin CoFeB/Ta/Co/Pd/Co reference layer has a comparable TMR ratio (near 80%) as that with thick reference layer after annealing at 280 °C. The pMTJ with thin reference layer has a total thickness less than 15 nm, thereby significantly increasing the etching margin required for integration of high density pMTJ array on wafers with form factor of 300 mm and beyond.

Evaluation of phase transformation in ferromagnetic shape memory Fe-Pd alloy by magnetic Barkhausen noise

Science.gov (United States)

Furuya, Yasubumi; Tamoto, Shizuka; Kubota, Takeshi; Okazaki, Teiko; Hagood, Nesbitt W.; Spearing, S. Mark

2002-07-01

The possibility to detect the phase transformation with martensites by heating or cooling as well as stress-loading in ferromagnetic shape memory Fe-30at percent Pd alloy thin foil by using magnetic Markhausen noise sensor was studied. MBHN is caused by the irregular interactions between magnetic domain and thermally activated martensite twins during magnetization. In general, the envelope of the MBHN voltage versus time signals in Fe-29at percent Pd ribbon showed two peaks during magnetization, where secondary peak at intermediate state of magnetization process decreased with increasing temperature, while the MBHN envelopes in pure iron did not change with increasing temperature. The variety of MBHN due to the phase transformation was apt to arise at higher frequency part of spectrum during intermediate state of magnetization process and it decreased with disappearance of martensite twins. Besides, MBHN increased monotonically with increasing loading stress and then, it decreased with unloading, however MBHN showed large hysteresis between loading and unloading passes. Based on the experimental results from MBHN measurements for both thermoelastic and stress-induced martensite phase transformations in Fe-30at percent Pd ribbon samples, MBHN method seems a useful technique to non-destructive evaluation of martensite phase transformation of ferromagnetic shape memory alloy.

Structure and magnetism of ultrathin Co and Fe films epitaxially grown on Pd/Cu(0 0 1)

International Nuclear Information System (INIS)

Lu, Y.F.; Przybylski, M.; Yan, L.; Barthel, J.; Meyerheim, H.L.; Kirschner, J.

2005-01-01

A contribution originating from the Co/Pd and Fe/Pd interfaces to the magneto-optical Kerr effect (MOKE) rotation is analyzed for Co and/or Fe films grown on a Pd-buffer-monolayer on Cu(0 0 1). A clear increase of the MOKE signal in comparison to the Co(Fe) films grown directly on Cu(0 0 1) is detected. An interpretation is supported by similar observations for Co films grown on Pd(1 1 0) and Pd(0 0 1). In particular, the sign reversal of the Kerr loops with increasing thickness of the Co(Fe) films is discussed. Magneto-optical effects are separated from the real magnetization and its dependence on the film thickness

Magnetotransport in Pd-rich PdFe alloys

Czech Academy of Sciences Publication Activity Database

Kudrnovský, Josef; Drchal, Václav; Turek, Ilja

2013-01-01

Roč. 26, č. 5 (2013), s. 1749-1752 ISSN 1557-1939 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional support: RVO:68378271 ; RVO:68081723 Keywords : galvanomagnetic transport * Pd-rich PdFe * long-range order * effect of temperature * anisotropic magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2013

Synthesis and characterization of NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst for hydrogenation reaction

Energy Technology Data Exchange (ETDEWEB)

Karaoğlu, E., E-mail: ekaraoglu@fatih.edu.tr [Department of Chemistry, Faculty of Arts and Sciences, Fatih University, 34500 B. Cekmece, Istanbul (Turkey); Özel, U.; Caner, C.; Baykal, A.; Summak, M.M. [Department of Chemistry, Faculty of Arts and Sciences, Fatih University, 34500 B. Cekmece, Istanbul (Turkey); Sözeri, H. [TUBITAK-UME, National Metrology Institute, PO Box 54, 41470 Gebze-Kocaeli (Turkey)

2012-12-15

Graphical abstract: Display Omitted Highlights: ► Novel superparamagnetic NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst was fabricated through co-precipitation. ► It could be reused several times without significant loss in catalytic activity for hydrogenation reaction. ► No further modification of the NiFe{sub 2}O{sub 4}–Pd magnetically recyclable catalyst is necessary for utilization as catalyst. -- Abstract: Herein we report the fabrication and characterization magnetically recyclable catalysts of NiFe{sub 2}O{sub 4}–Pd nanocomposite as highly effective catalysts for reduction reactions in liquid phase. The reduction Pd{sup 2+} was accomplished with polyethylene glycol 400 (PEG-400) instead of sodium borohydride (NaBH{sub 4}) and NiFe{sub 2}O{sub 4} nanoparticles was prepared by sonochemically using FeCI{sub 3}·6H{sub 2}O and NiCl{sub 2}. The chemical characterization of the product was done with X-ray diffractometry, Infrared spectroscopy, transmission electron microscopy, UV–Vis spectroscopy, thermal gravimetry and inductively coupled plasma. Thus formed NiFe{sub 2}O{sub 4}–Pd MRCs showed a very high activity in reduction reactions of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase. It was found out that the catalytic activity of NiFe{sub 2}O{sub 4}–Pd MRCs on the reduction of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase are between 99–93% and 98–93%, respectively. Magnetic character of this system allowed recovery and multiple use without significant loss of its catalytic activity. It is found that NiFe{sub 2}O{sub 4}–Pd MRCs showed very efficient catalytic activity and multiple usability.

Magnetization process in FePd thin films

International Nuclear Information System (INIS)

Klein, O.; Samson, Y.; Marty, A.; Guillous, S.; Viret, M.; Fermon, C.; Alloul, H.

2001-01-01

A custom made magnetic force microscope is used to study the magnetization process in thin films of FePd throughout the entire hysteresis loop. The 40 nm thick sample has a strong perpendicular anisotropy, which leads to a maze of 80 nm wide stripes of opposite polarity in the remanent state. The growth of M, when H increases, happens through an unwinding of the reversed domain along their axis. Together with the length recession, the reversed domain width also contracts with increasing field. The later effect is estimated by comparison of our images with magneto-optical Kerr measurements. A large disorder in the propagation process of the domain walls is observed. It is also found that the bubble configuration near the saturation field is unstable. [copyright] 2001 American Institute of Physics

μ+ studies of dilute PdFe alloys

International Nuclear Information System (INIS)

Nagamine, K.; Nishida, N.; Yamazaki, T.; British Columbia Univ., Vancouver

1976-08-01

In order to investigate the ordering mechanism among giant moments around Fe impurities in Pd, μ + was used to probe the conduction electron polarization in PdFe alloys above and below the critical concentration of 0.1 at. % with reference to pure Pd. Below the ordering temperatures the broadening of the μ + field for 0.015 at. % Fe is substantially larger than that for 0.28 at. % Fe, when normalized to the bulk magnetization. The results can be explained in terms of an RKKY spin oscillation in the region outside the giant moment. (author)

Austenite-martensite transformation in electrodeposited Fe70Pd30 NWs: a step towards making bio-nano-actuators tested on in vivo systems

Science.gov (United States)

Zuzek Rozman, K.; Pecko, D.; Trafela, S.; Samardzija, Z.; Spreitzer, M.; Jaglicic, Z.; Nadrah, P.; Zorko, M.; Bele, M.; Tisler, T.; Pintar, A.; Sturm, S.; Kostevsek, N.

2018-03-01

Fe69±3Pd31±3 nanowires (NWs) with lengths of a few microns and diameters of 200 nm were synthesized via template-assisted pulsed electrodeposition into alumina-based templates. The as-deposited Fe69±3Pd31±3 NWs exhibited α-Fe (bcc-solid solution of Fe, Pd) nanocrystalline structure as seen from the x-ray diffraction (XRD), that got confirmed by transmission electron microscopy (TEM) with some larger grains up 50 nm observed. Annealing of the as-deposited Fe69±3Pd31±3 NWs at 1173 K/45 min was followed by quenching in ice water and resulted in a transformation to the fcc crystal structure (XRD) with grain sizes up to 200 nm (TEM). To induce the austenite-to-martensite, i.e., fcc-to-fct phase transformation the fcc Fe69±3Pd31±3 NWs were cooled to 73 K. The XRD showed the disappearance of the (200) fcc reflection (at room temperature) and the appearance of the (200) fct reflection (at 73 K), confirming the fcc-to-fct transformation took place. The magnetic measurements revealed that the fcc Fe69±3Pd31±3 NWs measured at low temperatures (50 K) had a larger coercivity than at room temperature, which suggests the fct phase was present in the undercooled state, exhibiting a larger magnetocrystalline anisotropy than the fcc phase present at room temperature. As part of our interest in magnetic-shape-memory actuators, the as-deposited Fe69±3Pd31±3 NWs were tested for toxicity on zebrafish. In vivo tests showed no acute lethal or sub-lethal effects, which implies that the Fe69±3Pd31±3 NWs have the potential to be used as nano-actuators in biomedical applications.

Influence of surface topography on RBS measurements: case studies of (Cu/Fe/Pd) multilayers and FePdCu alloys nanopatterned by self-assembly

Science.gov (United States)

Krupinski, M.; Perzanowski, M.; Zabila, Y.; Zarzycki, A.; Marszałek, M.

2017-03-01

In this paper the influence of surface topography on Rutherford backscattering spectrometry (RBS) is discussed. (Cu/Fe/Pd) multilayers with total thickness of about 10 nm were deposited by physical vapor deposition on self-organized array of SiO2 nanoparticles with the size of 50 nm and 100 nm. As a reference, the multilayered systems were also prepared on flat substrates under the same conditions. After the deposition, morphology of the systems was studied by scanning electron microscopy (SEM), while chemical analysis was performed using Rutherford backscattering spectrometry. It was found that the RBS spectra and determined compositions for flat and patterned multilayers differ. The difference is discussed by taking into account the effect of additional inelastic scattering and energy straggling occurring due to developed topography of patterned systems. Then, the multilayers were annealed in 600 °C in order to obtain FePdCu alloy. The phenomenon of solid-state dewetting resulted in the formation of isolated alloy islands on the top of SiO2 nanoparticles. The SEM and RBS analysis were repeated showing correlation between the size distribution of obtained alloy islands and broadening of peaks appearing in RBS spectra. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8-12 November 2016, Ha Long City, Vietnam.

Effects of atomic and magnetic order on electronic transport in Pd-richPd-Fe alloys

Czech Academy of Sciences Publication Activity Database

Kudrnovský, Josef; Drchal, Václav; Khmelevskyi, S.; Turek, Ilja

2011-01-01

Roč. 84, č. 21 (2011), "214436-1"-"214436-8" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : residual resistivity * anisotropic magnetoresistance * anomalous Hall effect * PdFe-alloys * spin-orbit coupling * theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

Structural and magnetic properties of Gd/Fe multilayers grown by pulsed laser deposition

DEFF Research Database (Denmark)

Kant, K. Mohan; Bahl, Christian Robert Haffenden; Pryds, Nini

2010-01-01

This work investigates the structural and the magnetic properties of Gd/Fe multilayered thin films grown by pulsed laser deposition onto Si (001) substrates at room temperature. he Fe layer thickness is varied from 70 to 150 nm and its effect on the structural and magnetic properties of Fe/Gd/Fe ...

Velocity dependence of enhanced dynamic hyperfine field for Pd ions swiftly recoiling in magnetized Fe

International Nuclear Information System (INIS)

Stuchbery, A.E.; Ryan, G.C.; Bolotin, H.H.; Sie, S.H.

1980-01-01

The velocity-dependence of the magnitude of the enchanced dynamic hyperfine magnetic field (EDF) manifest at nuclei of 108 Pd ions swiftly recoiling through thin magnetized Fe has been investigated at ion velocities higher than have heretofore been examined for the heavier nuclides (i.e., at initial recoil velocities (v/Zv 0 )=0.090 and 0.160, v 0 =c/137). These results for 108 Pd, when taken in conjunction with those of prior similar measurements for 106 Pd at lower velocities, and fitted to a velocity dependence for the EDF, give for the Pd isotopes over the extended velocity range 1.74 0 )<=7.02, p=0.41+-0.15; a result incompatible with previous attributions of a linear velocity dependence for the field

Magnetically separable Fe3O4@DOPA–Pd: a heterogeneous catalyst for aqueous Heck reaction

Data.gov (United States)

U.S. Environmental Protection Agency — Magnetically separable Fe3O4@DOPA–Pd catalyst has been synthesized via anchoring of palladium over dopamine-coated magnetite via co-ordinate interaction and the...

Perpendicular magnetic anisotropy in Co{sub X}Pd{sub 100−X} alloys for magnetic tunnel junctions

Energy Technology Data Exchange (ETDEWEB)

Clark, B.D.; Natarajarathinam, A.; Tadisina, Z.R. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487 (United States); Chen, P.J.; Shull, R.D. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Gupta, S., E-mail: Sgupta@eng.ua.edu [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487 (United States)

2017-08-15

Highlights: • CoPd alloy perpendicular anisotropy dependent on composition and thickness. • CIPT results show that TMR tracks with PMA of CoPd. • Potential replacement for Co/Pd multilayers. - Abstract: CoFeB/MgO-based perpendicular magnetic tunnel junctions (p-MTJ’s) with high anisotropy and low damping are critical for spin-torque transfer random access memory (STT-RAM). Most schemes of making the pinned CoFeB fully perpendicular require ferrimagnets with high damping constants, a high temperature-grown L1{sub 0} alloy, or an overly complex multilayered synthetic antiferromagnet (SyAF). We report a compositional study of perpendicular Co{sub x}Pd alloy-pinned Co{sub 20}Fe{sub 60}B{sub 20}/MgO based MTJ stacks, grown at moderate temperatures in a planetary deposition system. The perpendicular anisotropy of the Co{sub x}Pd alloy films can be tuned based on the layer thickness and composition. The films were characterized by alternating gradient magnetometry (AGM), energy-dispersive X-rays (EDX), and X-ray diffraction (XRD). Current-in-plane tunneling (CIPT) measurements have also been performed on the compositionally varied Co{sub x}Pd MTJ stacks. The Co{sub x}Pd alloy becomes fully perpendicular at approximately x = 30% (atomic fraction) Co. Full-film MTJ stacks of Si/SiO{sub 2}/MgO (13)/Co{sub X}Pd{sub 100−x} (50)/Ta (0.3)/CoFeB (1)/MgO (1.6)/CoFeB (1)/Ta (5)/Ru (10), with the numbers enclosed in parentheses being the layer thicknesses in nm, were sputtered onto thermally oxidized silicon substrates and in-situ lamp annealed at 400 °C for 5 min. CIPT measurements indicate that the highest TMR is observed for the CoPd composition with the highest perpendicular magnetic anisotropy.

Magnetically Separable Fe3O4@DOPA-Pd: A Heterogeneous Catalyst for Aqueous Heck Reaction

Science.gov (United States)

Magnetically separable Fe3O4@DOPA-Pd catalyst has been synthesized via anchoring of palladium over dopamine-coated magnetite via non-covalent interaction and the catalyst is utilized for expeditious Heck coupling in aqueous media.

Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

NARCIS (Netherlands)

Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

2016-01-01

Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

Magnetic domain observation of FeCo thin films fabricated by alternate monoatomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Ohtsuki, T., E-mail: ohtsuki@spring8.or.jp; Kotsugi, M.; Ohkochi, T. [Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kojima, T.; Mizuguchi, M.; Takanashi, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

2014-01-28

FeCo thin films are fabricated by alternate monoatomic layer deposition method on a Cu{sub 3}Au buffer layer, which in-plane lattice constant is very close to the predicted value to obtain a large magnetic anisotropy constant. The variation of the in-plane lattice constant during the deposition process is investigated by reflection high-energy electron diffraction. The magnetic domain images are also observed by a photoelectron emission microscope in order to microscopically understand the magnetic structure. As a result, element-specific magnetic domain images show that Fe and Co magnetic moments align parallel. A series of images obtained with various azimuth reveal that the FeCo thin films show fourfold in-plane magnetic anisotropy along 〈110〉 direction, and that the magnetic domain structure is composed only of 90∘ wall.

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.

L1{sub 0} phase formation in ternary FePdNi alloys

Energy Technology Data Exchange (ETDEWEB)

Montes-Arango, A.M. [Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115 (United States); Bordeaux, N.C. [Department of Chemical Engineering, Northeastern University, Boston, MA 02115 (United States); Liu, J.; Barmak, K. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027 (United States); Lewis, L.H., E-mail: lhlewis@neu.edu [Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115 (United States); Department of Chemical Engineering, Northeastern University, Boston, MA 02115 (United States)

2015-11-05

Metallurgical routes to highly metastable phases are required to access new materials with new functionalities. To this end, the stability of the tetragonal chemically ordered L1{sub 0} phase in the ternary Fe–Pd–Ni system is quantified to provide enabling information concerning synthesis of L1{sub 0}-type FeNi, a highly attractive yet highly elusive advanced permanent magnet candidate. Fe{sub 50}Pd{sub 50−x}Ni{sub x} (x = 0–7 at%) samples were arc-melted and annealed at 773 K (500 °C) for 100 h to induce formation of the chemically ordered L1{sub 0} phase. Coupled calorimetry, structural and magnetic investigations allow determination of an isothermal section of the ternary Fe–Pd–Ni phase diagram featuring a single phase L1{sub 0} region near the FePd boundary for x < 6 at%. It is demonstrated that increased Ni content in Fe{sub 50}Pd{sub 50−x}Ni{sub x} alloys systematically decreases the order-disorder transition temperature, resulting in a lower thermodynamic driving force for the ordering phase transformation. The Fe{sub 50}Pd{sub 50−x}Ni{sub x} L1{sub 0} → fcc disordering transformation is determined to occur via a two-step process, with compositionally-dependent enthalpies and transition temperatures. These results highlight the need to investigate ternary alloys with higher Ni content to determine the stability range of the L1{sub 0} phase near the FeNi boundary, thereby facilitating kinetic access to the important L1{sub 0} FeNi ferromagnetic phase. - Highlights: • Chemical ordering in FePdNi enhances intrinsic and extrinsic magnetic properties. • 773 K annealed FePdNi alloys studied show a stable L1{sub 0} phase for Ni ≤ 5.2 at%. • Chemical disordering in FePdNi occurs by a previously unreported two-step process. • Ni additions to FePd dramatically decrease the chemical order-disorder temperature. • The chemical-ordering transformation kinetics are greatly affected by Ni content.

Chemical synthesis, phase transformation and magnetic proprieties of FePt and FePd nanoparticles

International Nuclear Information System (INIS)

Delattre, Anastasia

2010-01-01

This work aims at understanding the chemical synthesis of FePt and FePd nanoparticles (NPs), and at exploring how to implement the phase transformation from the chemically disordered to the L10 phase, without coalescence. Using hexadecanenitrile instead of oleylamine, we obtain NPs with a more homogenous internal composition, instead of core-shell NPs. Through a systematic study (designed experiment relying on Taguchi tables), we developed the FePd synthesis, while evidencing the role of each ligand and of the reductor. To induce the crystalline phase transformation while avoiding coalescence, we explored two ways. In the first one, atomic vacancies are introduced in the NPs through light ion irradiation, atomic mobility being ensured by annealing at moderate temperature (300 C). As a result, the blocking temperature is multiplied by 4, due to anisotropy enhancement. However, strong chemical ordering in the L10 phase cannot be achieved. The second approach relies on the dispersion of the NPs in a salt (NaCl) matrix, prior to annealing at 700 C: high chemical ordering is achieved, and the blocking temperature is beyond 400 C. We then developed a single-step process to remove the salt by dissolution in water and to re-disperse NPs in stable aqueous or organics solutions. These high magnetic anisotropy NPs are then readily available for further chemical or manipulation steps, with applied perspectives in areas such as data storage, or biology. (author)

Ferromagnetism of Pd-Fe (abstract)

Science.gov (United States)

Griffith, G.; Carnegie, D. W., Jr.; Claus, H.

1984-03-01

We present new low field ac susceptibility measurements on Pd1-xFex alloys (0.002≤X<0.01). The Curie temperature TC, determined from these measurements, are significantly lower than those previously obtained in higher magnetic fields [G. J. Nieuwenhuys, Adv. Phys. 24, 515 (1975)]. We also found that for a given sample, TC depends very sensitively on its heat treatment. As an example, for an alloy with 0.4 at. % Fe, TC can be varied between 4 and 10 K. In other alloys, like PdNi or RhNi similar changes in TC are due to changes in the degree of atomic short-range order [S. Crane, D. W. Carnegie, Jr., and H. Claus, J. Appl. Phys. 53, 2179 (1982)]. However, for PdFe we show evidence that the changes in TC are due to absorption of small amounts of oxygen, the samples with the highest amount of oxygen having the highest TC. It thus seems that oxygen has the opposite effect from hydrogen on the exchange enhanced susceptibility of Pd [J. A. Mydosh, Phys. Rev. Lett. 33, 1562 (1974)].

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.

Polarized neutron study of the magnetic mesostructure in (Pd{sub 1-x}Fe{sub x}){sub 1-y}Mn{sub y}

Energy Technology Data Exchange (ETDEWEB)

Gordeev, G.P.; Axelrod, L.A.; Lazebnik, I.M.; Zabenkin, V.N. [Petersburg Nuclear Physics Institute, 188300, Gatchina (Russian Federation); Wagner, V. [Physikalisch-Technische Bundesanstalt, 38116, Braunschweig (Germany)

2002-07-01

In PdFeMn alloys with different Fe-atom concentrations, the behaviour of both mean magnetization and neutron depolarization in the magnetization/demagnetization process was observed by three-dimensional analysis of neutron-beam polarization. Both magnetization and depolarization have a hysteresis loop for the same values of an applied field. Depolarization loops are sharply distinguished for different alloys. This gives evidence of different magnetic mesostructures in these alloys. (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.

What are the mesoscopic magnetic inhomogeneities in the dilute PdFeMn alloy? Polarized neutron study

Energy Technology Data Exchange (ETDEWEB)

Gordeev, G.; Axelrod, L.; Zabenkin, V.; Lazebnik, I.; Grigoriev, S.; Wagner, V.; Eckerlebe, H

2003-07-01

The 3D analysis of neutron depolarization was carried out for different thermomagnetic treatment of the dilute PdFeMn alloy versus temperature and magnetic field applied in magnetizing/demagnetizing cycles. Both the macroscopic magnetization and the mean fluctuation of local magnetization behavior were subtracted from experimental data. A complicated behavior of the latter was observed. The hysteresis of local magnetization fluctuations is found out but that of macroscopic magnetization is practically absent. The effort to apply the simple model for the description of magnetic inhomogeneities was made in order to understand the mesostructure of this alloy.

Effect of Magnetic Field on Surface Morphology and Magnetic Properties of FeCu/Cu Nano layers Prepared by Electrodeposition Technique: Investigation of Magneto-hydrodynamic Effect

Directory of Open Access Journals (Sweden)

M. Merikhi

2015-10-01

Full Text Available In this paper, the effect of magnetic field on the morphology, structure and magnetic properties of electrodeposited FeCu/Cu thin films was investigated. The films were deposited on Au2PdAg/glass substrates using electrodeposition technique in potentiostatic control. The magnetic fields of 5000 and 7000 Oe were applied on deposition bath during deposition. Two series of thin films were prepared in the same deposition conditions, one in the presence and the other in absence of magnetic field and the products were compared. The results indicate that applying the magnetic field has a significant effect on the growth process, i.e. morphology, crystal structure and magnetic properties of the films. The morphology and structure of the FeCu/Cu Nano layers were studied using X-ray diffraction (XRD and scanning electron microscopy (SEM. The weight percentages of the elements in the deposited multilayers were determined by energy dispersive X-ray spectroscopy (EDS. Magnetic properties of thin films were studied using the vibrating sample magnetometer (VSM.

A facile one-pot solvothermal method for synthesis of magnetically recoverable Pd-Fe3O4 hybrid nanocatalysts for the Mizoroki-Heck reaction

Science.gov (United States)

Zhen, Fangchen; Ran, Maofei; Chu, Wei; Jiang, Chengfa; Sun, Wenjing

2018-03-01

Pd-Fe3O4 hybrid nanostructures were prepared using a simple one-pot hydrothermal method. The prepared materials were characterized by Fourier transform-infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, N2 adsorption-desorption, and vibrating sample magnetometry. This self-assembled nanosystem acted as an efficient magnetically recyclable noble metal-based multi-functional nanocatalyst. It showed excellent catalytic activity and stability for the Heck reaction of iodobenzene and styrene under mild conditions. The methods used to prepare the Pd-Fe3O4 catalysts were simple and low-cost, which will be useful for the large-scale development and application of a magnetically recoverable Pd catalyst.

Gilbert damping constant of FePd alloy thin films estimated by broadband ferromagnetic resonance

Directory of Open Access Journals (Sweden)

Kawai T.

2014-07-01

Full Text Available Magnetic relaxation of FePd alloy epitaxial thin films with very flat surfaces prepared on MgO(001 substrate are measured by in-plane broadband ferromagnetic resonance (FMR. Magnetic relaxation is investigated as Δω for FMR absorption peak by frequency sweep measurements. ΔH is calculated by using the measured Δω. Gilbert damping constant, α, is estimated by employing a straight line fitting of the resonant frequency dependence of ΔH. The α value for an FePd film deposited at 200 ˚C, which shows disordered A1 structure, is 0.010 and ΔH0, which is frequency independent part of ΔH, is 10 Oe. The α value for a film annealed at 400 ˚C, which shows partially L10 ordered structure (S=0.32, is 0.013, which is slightly larger than that for the disorder A1 structure film. However, ΔH0 for the annealed film is 85 Oe, which is much larger than that for the film with disordered structure. The results show that the magnetic relaxation of the 400 ˚C annealed film is mainly dominated by ΔH0, which is related with magnetic in-homogeneity caused by the appearance of perpendicular anisotropy of partially ordered phase.

Magnetic nanowires (Fe, Fe-Co, Fe-Ni – magnetic moment reorientation in respect of wires composition

Directory of Open Access Journals (Sweden)

Kalska-Szostko Beata

2015-03-01

Full Text Available Magnetic nanowires of Fe, Fe-Co, and Fe-Ni alloy and layered structure were prepared by electrochemical alternating current (AC deposition method. The morphology of the nanowires in and without the matrix was studied by energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM, and X-ray diffraction (XRD, respectively. The wires either show strong dependence on the combination of elements deposition (alloy or layered or chemical composition (Co or Ni. The magnetic properties of the nanostructures were determined on the basis of Mössbauer spectroscopy (MS.

Enhancement in (BHmax of PLD-made isotropic Nd-Fe-B thick film magnets deposited on Si substrates

Directory of Open Access Journals (Sweden)

M. Nakano

2017-05-01

Full Text Available Increase in Nd contents of a PLD-made isotropic Nd-Fe-B thick-film magnet enabled us to enhance the thickness of the film magnet deposited on a Si substrate because the linear expansion coefficient of Nd is an intermediate value between Nd2Fe14B and Si. The large amount of Nd, however, degraded the residual magnetic polarization and (BHmax. In the study, we reduced the Nd contents of each Nd-Fe-B film by inserting a Nd or a Nd-rich Nd-Fe-B buffer layer between a Nd-Fe-B film and a Si substrate in order to suppress the mechanical destruction together with the improvement in magnetic properties. It was found that the mechanical property of a Nd-Fe-B film comprising the Nd-Fe-B buffer layer in the thickness range from 10 to 60 μm was superior than that of a sample with the Nd buffer layer. Resultantly, an average (BHmax value of Nd-Fe-B films with each Nd-Fe-B buffer layer deposited on Si substrates could be enhanced by approximately 15 kJ/m3 compared to that of non-buffer-layered films.

Physical Vapor Deposition of Thin Films

Science.gov (United States)

Mahan, John E.

2000-01-01

A unified treatment of the theories, data, and technologies underlying physical vapor deposition methods With electronic, optical, and magnetic coating technologies increasingly dominating manufacturing in the high-tech industries, there is a growing need for expertise in physical vapor deposition of thin films. This important new work provides researchers and engineers in this field with the information they need to tackle thin film processes in the real world. Presenting a cohesive, thoroughly developed treatment of both fundamental and applied topics, Physical Vapor Deposition of Thin Films incorporates many critical results from across the literature as it imparts a working knowledge of a variety of present-day techniques. Numerous worked examples, extensive references, and more than 100 illustrations and photographs accompany coverage of: * Thermal evaporation, sputtering, and pulsed laser deposition techniques * Key theories and phenomena, including the kinetic theory of gases, adsorption and condensation, high-vacuum pumping dynamics, and sputtering discharges * Trends in sputter yield data and a new simplified collisional model of sputter yield for pure element targets * Quantitative models for film deposition rate, thickness profiles, and thermalization of the sputtered beam

Vertically aligned carbon nanotube growth by pulsed laser deposition and thermal chemical vapor deposition methods

International Nuclear Information System (INIS)

Sohn, Jung Inn; Nam, Chunghee; Lee, Seonghoon

2002-01-01

We have grown vertically aligned carbon nanotubes on the various substrates such as a planar p-type Si(1 0 0) wafer, porous Si wafer, SiO 2 , Si 3 N 4 , Al 2 O 3 , and Cr by thermal chemical vapor deposition (CVD) at 800 deg.C, using C 2 H 2 gas as a carbon source and Fe catalyst films deposited by a pulsed laser on the substrates. The Fe films were deposited for 5 min by pulsed laser deposition (PLD). The advantage of Fe deposition by PLD over other deposition methods lies in the superior adhesion of Fe to a Si substrate due to high kinetic energies of the generated Fe species. Scanning electron microscopy (SEM) images show that vertically well-aligned carbon nanotubes are grown on Fe nanoparticles formed from the thermal annealing of the Fe film deposited by PLD on the various substrates. Atomic force microscopy (AFM) images show that the Fe film annealed at 800 deg.C is broken to Fe nanoparticles of 10-50 nm in size. We show that the appropriate density of Fe nanoparticles formed from the thermal annealing of the film deposited by PLD is crucial in growing vertically aligned carbon nanotubes. Using a PLD and a lift-off method, we developed the selective growth of carbon nanotubes on a patterned Fe-coated Si substrate

Lithium-ions diffusion kinetic in LiFePO4/carbon nanoparticles synthesized by microwave plasma chemical vapor deposition for lithium-ion batteries

Science.gov (United States)

Gao, Chao; Zhou, Jian; Liu, Guizhen; Wang, Lin

2018-03-01

Olivine structure LiFePO4/carbon nanoparticles are synthesized successfully using a microwave plasma chemical vapor deposition (MPCVD) method. Microwave is an effective method to synthesize nanomaterials, the LiFePO4/carbon nanoparticles with high crystallinity can shorten diffusion routes for ionic transfer and electron tunneling. Meanwhile, a high quality, complete and homogenous carbon layer with appropriate thickness coating on the surface of LiFePO4 particles during in situ chemical vapor deposition process, which can ensure that electrons are able to transfer fast enough from all sides. Electrochemical impedance spectroscopy (EIS) is carried out to collect information about the kinetic behavior of lithium diffusion in LiFePO4/carbon nanoparticles during the charging and discharging processes. The chemical diffusion coefficients of lithium ions, DLi, are calculated in the range of 10-15-10-9 cm2s-1. Nanoscale LiFePO4/carbon particles show the longer regions of the faster solid-solution diffusion, and corresponding to the narrower region of the slower two-phase diffusion during the insertion/exaction of lithium ions. The CV and galvanostatic charge-discharge measurements show that the LiFePO4/carbon nanoparticles perform an excellent electrochemical performance, especially the high rate capacity and cycle life.

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.

Pd- and Ca-doped iron oxide for ethanol vapor sensing

International Nuclear Information System (INIS)

Neri, G.; Bonavita, A.; Ipsale, S.; Rizzo, G.; Baratto, C.; Faglia, G.; Sberveglieri, G.

2007-01-01

Iron oxide thin films doped with Ca and Pd, prepared by a liquid-phase deposition method (LPD) from aqueous solution, have been investigated as potential ethanol gas sensors. SEM and XRD analyses were used to characterize Fe 2 O 3 LPD films. Hematite (α-Fe 2 O 3 ), having an average crystallite size in the range between 20 and 30 nm, was the only crystalline phase detected on all undoped and doped films. The electrical response towards ethanol (100-500 ppm) has been studied in the temperature range of 300-500 deg. C. Both Ca and Pd promoters have shown a positive effect on the sensitivity of Fe 2 O 3 films at the lower temperature investigated, whereas at higher temperature the undoped Fe 2 O 3 film has shown better performances. The sensing properties of undoped and doped Fe 2 O 3 thin films towards different interfering gases like NO 2 , CO and NH 3 have been also investigated, showing that the selectivity to ethanol benefits of the Ca addition

Electrocatalytic Reduction-oxidation of Chlorinated Phenols using a Nanostructured Pd-Fe Modified Graphene Catalyst

International Nuclear Information System (INIS)

Shi, Qin; Wang, Hui; Liu, Shaolei; Pang, Lei; Bian, Zhaoyong

2015-01-01

A Pd-Fe modified graphene (Pd-Fe/G) catalyst was prepared by the Hummers oxidation method and bimetallic co-deposition method. The catalyst was then characterized by various characterization techniques and its electrochemical property toward the electrocatalytic reduction-oxidation of chlorinated phenols was investigated by using cyclic voltammetry and differential pulse voltammetry. The results of the characterization show that the Pd-Fe/G catalyst in which the weight proportion of Pd and Fe is 1:1 has an optimal surface performance. The diameter of the Pd-Fe particles is approximately 5.2 ± 0.3 nm, with a uniform distribution on the supporting graphene. This is smaller than the Pd particles of a Pd-modified graphene (Pd/G) catalyst. The Pd-Fe/G catalyst shows a higher electrocatalytic activity than the Pd/G catalyst for reductive dechlorination when feeding with hydrogen gas. The reductive peak potentials of −0.188 V, −0.836 V and −0.956 V in the DPV curves are attributed to the dechlorination of ortho-Cl, meta-Cl, and para-Cl in 2-chlorophenol, 3-chlorophenol and 4-chlorophenol, respectively. In accordance with an analysis of the frontier orbital theory, the order of ease of dechlorination with Pd-Fe/G catalyst is 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. The Pd-Fe/G catalyst has a greater activity than the Pd/G catalyst in accelerating the two-electron reduction of O_2 to H_2O_2, which is attributed to the higher current of the reduction peak at approximately −0.40 V when feeding with oxygen gas. Therefore, the Pd-Fe/G catalyst exhibits a higher electrocatalytic activity than the Pd/G catalyst for the reductive dechlorination and acceleration of the two-electron reduction of O_2 to H_2O_2.

Recovery of Platinum Group Metals from Spent Catalysts Using Iron Chloride Vapor Treatment

Science.gov (United States)

Taninouchi, Yu-ki; Okabe, Toru H.

2018-05-01

The recovery of platinum group metals (PGMs) from spent automobile catalysts is a difficult process because of their relatively low contents in the scrap. In this study, to improve the efficiency of the existing recycling techniques, a novel physical concentration method involving treatment with FeCl2 vapor has been examined. The reactions occurring between typical catalyst components and FeCl2 vapor are discussed from the thermodynamic point of view, and the validity of the proposed technique was experimentally verified. The obtained results indicate that the vapor treatment at around 1200 K (927 °C) can effectively alloy PGMs (Pt, Pd, and Rh) with Fe, resulting in the formation of a ferromagnetic alloy. It was also confirmed that cordierite and alumina (the major catalyst components) remained unreacted after the vapor treatment, while ceria species were converted into oxychlorides. The samples simulating the automobile catalyst were also subjected to magnetic separation after the treatment with FeCl2 vapor; as a result, PGMs were successfully extracted and concentrated in the form of a magnetic powder. Thus, the FeCl2 vapor treatment followed by magnetic separation can be utilized for recovering PGMs directly from spent catalysts as an effective pretreatment for the currently used recycling methods.

Polarized neutron study of the magnetic mesostructure in (Pd sub 1 sub - sub x Fe sub x) sub 1 sub - sub y Mn sub y

CERN Document Server

Gordeev, G P; Lazebnik, I M; Zabenkin, V N; Wagner, V

2002-01-01

In PdFeMn alloys with different Fe-atom concentrations, the behaviour of both mean magnetization and neutron depolarization in the magnetization/demagnetization process was observed by three-dimensional analysis of neutron-beam polarization. Both magnetization and depolarization have a hysteresis loop for the same values of an applied field. Depolarization loops are sharply distinguished for different alloys. This gives evidence of different magnetic mesostructures in these alloys. (orig.)

Synthesis and growth mechanism of Fe-catalyzed carbon nanotubes by plasma-enhanced chemical vapor deposition

International Nuclear Information System (INIS)

Jiang Jun; Feng Tao; Cheng Xinhong; Dai Lijuan; Cao Gongbai; Jiang Bingyao; Wang Xi; Liu Xianghuai; Zou Shichang

2006-01-01

Plasma-enhanced chemical vapor deposition (PECVD) was used to grow Fe-catalyzed carbon nanotubes (CNTs). The nanotubes had a uniform diameter in the range of about 10-20 nm. A base growth mode was responsible for the CNTs growth using a mixture of H 2 (60 sccm) and C 2 H 2 (15 sccm). For a mixture of H 2 (100 sccm) and C 2 H 2 (25 sccm), a complicated growth mechanism took place involving both the base growth and the tip growth. X-ray photoelectron spectroscopy measurements revealed that the grown CNTs contained C-H covalent bonds and Fe-C bonds located at the interface between them and the substrates. The factors determining the growth mechanism of CNTs are discussed and their growth mechanisms with the different gas ratios are suggested

AuPd Bimetallic Nanocrystals Embedded in Magnetic Halloysite Nanotubes: Facile Synthesis and Catalytic Reduction of Nitroaromatic Compounds

Directory of Open Access Journals (Sweden)

Lei Jia

2017-10-01

Full Text Available In this research, a facile and effective approach was developed for the preparation of well-designed AuPd alloyed catalysts supported on magnetic halloysite nanotubes (HNTs@Fe3O4@AuPd. The microstructure and the magnetic properties of HNTs@Fe3O4@AuPd were confirmed by transmission electron microscopy (TEM, high resolution TEM (HRTEM, energy-dispersive X-ray spectroscopy (EDS, and vibrating sample magnetometry (VSM analyses. The catalysts, fabricated by a cheap, environmentally friendly, and simple surfactant-free formation process, exhibited high activities during the reduction of 4-nitrophenol and various other nitroaromatic compounds. Moreover, the catalytic activities of the HNTs@Fe3O4@AuPd nanocatalysts were tunable via adjusting the atomic ratio of AuPd during the synthesis. As compared with the monometallic nanocatalysts (HNTs@Fe3O4@Au and HNTs@Fe3O4@Pd, the bimetallic alloyed HNTs@Fe3O4@AuPd nanocatalysts exhibited excellent catalytic activities toward the reduction of 4-nitrophenol (4-NP to 4-aminophenol. Furthermore, the as-obtained HNTs@Fe3O4@AuPd can be recycled several times, while retaining its functionality due to the stability and magnetic separation property.

Nanolaminated FeCoB/FeCo and FeCoB/NiFe soft magnetic thin films with tailored magnetic properties deposited by magnetron sputtering

Science.gov (United States)

Hida, Rachid; Falub, Claudiu V.; Perraudeau, Sandrine; Morin, Christine; Favier, Sylvie; Mazel, Yann; Saghi, Zineb; Michel, Jean-Philippe

2018-05-01

Thin films based on layers of Fe52Co28B20 (at%), Fe65Co35 (at%), and Ni80Fe20 (at%) were deposited by sputtering on 8″ bare Si and Si/200 nm-thermal-SiO2 wafers by simultaneous use of two or more cathodes. Due to the continuous rotation of the substrate cage, such that the substrates faced different targets alternately, the multilayers consisted of stacks of alternating, nanometer-thick regular layers. The composition of the films was determined by Rutherford Backscattering Spectrometry (RBS) and Nuclear Reactive Analysis (NRA), whereas Plasma Profiling Time of Flight Mass Spectrometry (PP-TOFMS) analysis gave depth profile information about the chemical elements. The structural and magnetic properties of the films were investigated by X-ray Diffraction and by TEM analysis, B-H loop tracer and high frequency single coil technique permeametry, respectively. The linear dependence of the coercivity of these thin films versus the grain size can be explained by the random anisotropy model. These novel, composite soft magnetic multilayers, with tunable in-plane anisotropy, allow operation at tunable frequencies, as shown by broadband (between 100 MHz and 10 GHz) RF measurements that exhibit a classical Landau-Lifschitz-Gilbert (LLG) behavior and, combine the magnetic properties of the individual materials in an advantageous way. This article presents a method to produce nanostructured soft magnetic multilayers, the properties of which can easily be tuned by choosing the ratio of the individual nanolayers. In this way it's possible to combine soft magnetic materials with complementary properties, e.g. high saturation magnetization, low coercivity, high specific resistivity and low magnetostriction

Magnetic properties of Co and Fe on Pt(111), Rh(111) and Pd(111): From single atoms to ultrathin films

Energy Technology Data Exchange (ETDEWEB)

Lehnert, Anne; Rusponi, Stefano; Etzkorn, Markus; Moulas, Geraud; Brune, Harald [IPN, EPF-Lausanne (Switzerland); Gambardella, Pietro [CREA, Catalan Institute of Nanotechnology (Spain); Bencok, Peter [ESRF, Grenoble (France)

2009-07-01

Single atoms of Co on Pt(111) are known to have a giant magnetic anisotropy energy (MAE) of 9.3 meV/atom. This is due to the reduced coordination and the strong spin-orbit coupling of the Pt 5d-states. In order to study the contribution of a highly polarizable substrate to the MAE, we investigated single Co atoms on Pd(111) and Rh(111) using X-ray magnetic circular dichroism (XMCD). We find a decreasing MAE moving from a 5d-substrate (Pt) to 4d-substrates (Pd and Rh). Co has a large orbital moment L of about 0.7 independent of the substrate. The easy axis is out-of-plane for Pt(111) and Pd(111) whereas it is in-plane for Co/Rh(111). Fe has on all substrates an out-of-plane easy axis, a very small anisotropy energy, and a L/S ratio of about 0.1. With increasing coverage the coordination number of the adatom increases and generally leads to a reduced MAE and orbital moment compared to the single atom. We measure one monolayer of Co and Fe on Pt(111) and Rh(111) and find MAE values <0.5 meV/atom. For 1 ML Co we find a substantial decrease in the L/S ratio to 0.19. However, the L/S ratio for 1 ML Fe on both substrates does not change much compared with the Fe single atom.

Research on chemical vapor deposition processes for advanced ceramic coatings

Science.gov (United States)

Rosner, Daniel E.

1993-01-01

Our interdisciplinary background and fundamentally-oriented studies of the laws governing multi-component chemical vapor deposition (VD), particle deposition (PD), and their interactions, put the Yale University HTCRE Laboratory in a unique position to significantly advance the 'state-of-the-art' of chemical vapor deposition (CVD) R&D. With NASA-Lewis RC financial support, we initiated a program in March of 1988 that has led to the advances described in this report (Section 2) in predicting chemical vapor transport in high temperature systems relevant to the fabrication of refractory ceramic coatings for turbine engine components. This Final Report covers our principal results and activities for the total NASA grant of $190,000. over the 4.67 year period: 1 March 1988-1 November 1992. Since our methods and the technical details are contained in the publications listed (9 Abstracts are given as Appendices) our emphasis here is on broad conclusions/implications and administrative data, including personnel, talks, interactions with industry, and some known applications of our work.

Structural characterization of epitaxial LiFe_5O_8 thin films grown by chemical vapor deposition

International Nuclear Information System (INIS)

Loukya, B.; Negi, D.S.; Sahu, R.; Pachauri, N.; Gupta, A.; Datta, R.

2016-01-01

We report on detailed microstructural and atomic ordering characterization by transmission electron microscopy in epitaxial LiFe_5O_8 (LFO) thin films grown by chemical vapor deposition (CVD) on MgO (001) substrates. The experimental results of LFO thin films are compared with those for bulk LFO single crystal. Electron diffraction studies indicate weak long-range ordering in LFO (α-phase) thin films in comparison to bulk crystal where strong ordering is observed in optimally annealed samples. The degree of long-range ordering depends on the growth conditions and the thickness of the film. Annealing experiment along with diffraction study confirms the formation of α-Fe_2O_3 phase in some regions of the films. This suggests that under certain growth conditions γ-Fe_2O_3-like phase forms in some pockets in the as-grown LFO thin films that then convert to α-Fe_2O_3 on annealing. - Highlights: • Atomic ordering in LiFe_5O_8 bulk single crystal and epitaxial thin films. • Electron diffraction studies reveal different level of ordering in the system. • Formation of γ-Fe_2O_3 like phase has been observed.

Mechanisms of stress generation and relaxation during pulsed laser deposition of epitaxial Fe-Pd magnetic shape memory alloy films on MgO

International Nuclear Information System (INIS)

Edler, Tobias; Mayr, S G; Buschbeck, Joerg; Mickel, Christine; Faehler, Sebastian

2008-01-01

Mechanical stress generation during epitaxial growth of Fe-Pd thin films on MgO from pulsed laser deposition is a key parameter for the suitability in shape memory applications. By employing in situ substrate curvature measurements, we determine the stress states as a function of film thickness and composition. Depending on composition, different stress states are observed during initial film growth, which can be attributed to different misfits. Compressive stress generation by atomic peening is observed in the later stages of growth. Comparison with ex situ x-ray based strain measurements allows integral and local stress to be distinguished and yields heterogeneities of the stress state between coherent and incoherent regions. In combination with cross-sectional TEM measurements the relevant stress relaxation mechanism is identified to be stress-induced martensite formation with (111) twinning

Critical Factors Controlling Pd and Pt Potential in Porphyry Cu–Au Deposits: Evidence from the Balkan Peninsula

Directory of Open Access Journals (Sweden)

Demetrios G. Eliopoulos

2014-03-01

Full Text Available Porphyry Cu–Au–Pd±Pt deposits are significant Au resources, but their Pd and Pt potential is still unknown. Elevated Pd, Pt (hundreds of ppb and Au contents are associated with typical stockwork magnetite-bornite-chalcopyrite assemblages, at the central parts of certain porphyry deposits. Unexpected high grade Cu–(Pd+Pt (up to 6 ppm mineralization with high Pd/Pt ratios at the Elatsite porphyry deposit, which is found in a spatial association with the Chelopech epithermal deposit (Bulgaria and the Skouries porphyry deposit, may have formed during late stages of an evolved hydrothermal system. Estimated Pd, Pt and Au potential for porphyry deposits is consistent with literature model calculations demonstrating the capacity of aqueous vapor and brine to scavenge sufficient quantities of Pt and Pd, and could contribute to the global platinum-group element (PGE production. Critical requirements controlling potential of porphyry deposits may be from the metals contained in magma (metasomatized asthenospheric mantle wedge as indicated by significant Cr, Co, Ni and Re contents. The Cr content may be an indicator for the mantle input.

Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

Science.gov (United States)

Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

2016-05-01

Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

Structure, morphology, and magnetic properties of Fe nanoparticles deposited onto single-crystalline surfaces

Directory of Open Access Journals (Sweden)

Armin Kleibert

2011-01-01

Full Text Available Background: Magnetic nanostructures and nanoparticles often show novel magnetic phenomena not known from the respective bulk materials. In the past, several methods to prepare such structures have been developed – ranging from wet chemistry-based to physical-based methods such as self-organization or cluster growth. The preparation method has a significant influence on the resulting properties of the generated nanostructures. Taking chemical approaches, this influence may arise from the chemical environment, reaction kinetics and the preparation route. Taking physical approaches, the thermodynamics and the kinetics of the growth mode or – when depositing preformed clusters/nanoparticles on a surface – the landing kinetics and subsequent relaxation processes have a strong impact and thus need to be considered when attempting to control magnetic and structural properties of supported clusters or nanoparticles.Results: In this contribution we focus on mass-filtered Fe nanoparticles in a size range from 4 nm to 10 nm that are generated in a cluster source and subsequently deposited onto two single crystalline substrates: fcc Ni(111/W(110 and bcc W(110. We use a combined approach of X-ray magnetic circular dichroism (XMCD, reflection high energy electron diffraction (RHEED and scanning tunneling microscopy (STM to shed light on the complex and size-dependent relation between magnetic properties, crystallographic structure, orientation and morphology. In particular XMCD reveals that Fe particles on Ni(111/W(110 have a significantly lower (higher magnetic spin (orbital moment compared to bulk iron. The reduced spin moments are attributed to the random particle orientation being confirmed by RHEED together with a competition of magnetic exchange energy at the interface and magnetic anisotropy energy in the particles. The RHEED data also show that the Fe particles on W(110 – despite of the large lattice mismatch between iron and tungsten – are

Domain wall motions in perpendicularly magnetized CoFe/Pd multilayer nanowire

DEFF Research Database (Denmark)

Meng, Zhaoliang; Kumar, Manoj; Qiu, Jinjun

2014-01-01

Current-induced domain wall (DW) motion is investigated in a 600nm wide nanowire using multilayer film with a structure of Ta(5nm)/Pd(5nm)/[CoFe(0.4nm)/Pd(1.2nm)]15/Ta(5nm) in terms of anomalous Hall effect measurements. It is found that motion of DWs can be driven by a current density as low as 1...

Structural and magnetic properties of granular CoPd multilayers

Energy Technology Data Exchange (ETDEWEB)

Vivas, L.G.; Figueroa, A.I.; Bartolomé, F. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Rubín, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Ciencia y Tecnología de Materiales y Fluidos, E-50018 Zaragoza (Spain); García, L.M. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Deranlot, C.; Petroff, F. [Unité Mixte de Physique CNRS/Thales, F-91767 Palaiseau Cedex, France and Université Paris-Sud, F-191405 Orsay Cedex (France); Ruiz, L.; González-Calbet, J.M [Dept. de Química Inorgánica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Brookes, N.B.; Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), CS40220, F-38043 Grenoble Cedex 9 (France); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain)

2016-02-15

Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. - Highlights: • CoPd granular nanolayers show perpendicular magnetic anisotropy. • Three magnetic phases are detected: hard-ferro, soft-ferro and superparamagnetism. • The nanoparticles have Co-core and CoPd alloy shell morphology.

Structural and magnetic properties of granular CoPd multilayers

International Nuclear Information System (INIS)

Vivas, L.G.; Figueroa, A.I.; Bartolomé, F.; Rubín, J.; García, L.M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J.M; Brookes, N.B.; Wilhelm, F.; Rogalev, A.; Bartolomé, J.

2016-01-01

Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. - Highlights: • CoPd granular nanolayers show perpendicular magnetic anisotropy. • Three magnetic phases are detected: hard-ferro, soft-ferro and superparamagnetism. • The nanoparticles have Co-core and CoPd alloy shell morphology.

Magnetic Pd-Fe{sub 3}O{sub 4} heterodimer nanocrystals as recoverable catalysts for ligand-free hiyama cross-coupling reactions

Energy Technology Data Exchange (ETDEWEB)

Lee, Woong Sup; Byun, Sang Moon; Kwon, Jung Min; Kim, B. Moon [Dept. of Chemistry, College of Natural Sciences, Seoul National University, Seoul (Korea, Republic of)

2016-12-15

Ligand-free Hiyama cross-coupling reaction was achieved through the use of Pd-Fe{sub 3}O{sub 4} heterodimeric nanocrystals (1 mol% in Pd) as recyclable catalysts. The nanocrystal catalysts exhibited good activities accommodating a variety of substrates including aryl bromides and iodides with substituents of varying electronic and steric properties. Furthermore, the nanocrystal catalyst could be conveniently recovered with the aid of an external magnet and recycled five times without the loss of catalytic activity to a considerable degree.

Characteristics of Iron-Palladium alloy thin films deposited by magnetron sputtering

Science.gov (United States)

Chiu, Y.-J.; Shen, C.-Y.; Chang, H.-W.; Jian, S.-R.

2018-06-01

The microstructural features, magnetic, nanomechanical properties and wettability behaviors of Iron-Palladium (FePd) alloy thin films are investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), nanoindentation and water contact angle (CA) techniques, respectively. The FePd alloy thin films were deposited on glass substrates using a magnetron sputtering system. The post-annealing processes of FePd alloy thin films were carried out at 400 °C and 750 °C and resulted in a significant increase of both the average grain size and surface roughness. The XRD analysis showed that FePd alloy thin films exhibited a predominant (1 1 1) orientation. The magnetic field dependence of magnetization of all FePd thin films are measured at room temperature showed the ferromagnetic characteristics. The nanoindentation with continuous stiffness measurement (CSM) is used to measure the hardness and Young's modulus of present films. The contact angle (θCA) increased with increasing surface roughness. The maximum θCA of 75° was achieved for the FePd alloy thin film after annealing at 750 °C and a surface roughness of 4.2 nm.

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.

Tuning stress-induced magnetic anisotropy and high frequency properties of FeCo films deposited on different curvature substrates

International Nuclear Information System (INIS)

Wang, Z.K.; Feng, E.X.; Liu, Q.F.; Wang, J.B.; Xue, D.S.

2012-01-01

It is important to control magnetic anisotropy of ferromagnetic materials. In this work, FeCo thin films are deposited on the curving substrates by electrochemical deposition to adjust the stress-induced magnetic anisotropy. The compressive stress is produced in the as-deposited films after the substrates are flattened. A simplified theoretical model of ferromagnetic resonance is utilized to measure the intrinsic magnetic anisotropy field and saturation magnetization. The results show that the stress-induced magnetic anisotropy and the resonance frequency increase with the increase of substrate curvature. The induced easy axis is perpendicular to the compressive stress direction.

Elimination of impurity phase formation in FePt magnetic thin films prepared by pulsed laser deposition

International Nuclear Information System (INIS)

Wang, Ying; Medwal, Rohit; Sehdev, Neeru; Yadian, Boluo; Tan, T.L.; Lee, P.; Talebitaher, A.; Ilyas, Usman; Ramanujan, R.V.; Huang, Yizhong; Rawat, R.S.

2014-01-01

The formation of impurity phases in FePt thin films severely degrades its magnetic properties. The X-ray diffraction patterns of FePt thin films, synthesized using pulsed laser deposition (PLD), showed peaks corresponding to impurity phases, resulting in softer magnetic properties. A systematic investigation was carried to determine the factors that might have led to impurity phase formation. The factors include (i) PLD target composition, (ii) substrate material, (iii) annealing parameters such as temperature, duration and ambience and (iv) PLD deposition parameters such as chamber ambience, laser energy fluence and target–substrate distance. Depositions on the different substrates revealed impurity phase formation only on Si substrates. It was found that the target composition, PLD chamber ambience, and annealing ambience were not the factors that caused the impurity phase formation. The annealing temperature and duration influenced the impurity phases, but are not the cause of their formation. A decrease in the laser energy fluence and increase of the target–substrate distance resulted in elimination of the impurity phases and enhancement in the magnetic and structural properties of FePt thin films. The energy of the ablated plasma species, controlled by the laser energy fluence and the target–substrate distance, is found to be the main factor responsible for the formation of the impurity phases.

The compositional, structural, and magnetic properties of a Fe{sub 3}O{sub 4}/Ga{sub 2}O{sub 3}/GaN spin injecting hetero-structure grown by metal-organic chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhonghua; Huang, Shimin [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Tang, Kun, E-mail: ktang@nju.edu.cn [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Gu, Shulin, E-mail: slgu@nju.edu.cn [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Zhu, Shunming [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Ye, Jiandong [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Nanjing University Institute of Optoelectronics at Yangzhou, Yangzhou 225009 (China); Xu, Mingxiang [Department of Physics, Southeast University, Nanjing 210096 (China); Wang, Wei; Zheng, Youdou [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China)

2016-12-01

Highlights: • The Fe{sub 3}O{sub 4}/Ga{sub 2}O{sub 3}/GaN hetero-structure has been fabricated by MOCVD successfully. • The formation mechanism of different layers in sample was revealed in details. • The properties of the hetero-structure have been presented and discussed extensively. • The effect of Ga diffusion on the magnetic properties of Fe{sub 3}O{sub 4} film has been shown. - Abstract: In this article, the authors have designed and fabricated a Fe{sub 3}O{sub 4}/Ga{sub 2}O{sub 3}/GaN spin injecting hetero-structure by metal-organic chemical vapor deposition. The compositional, structural, and magnetic properties of the hetero-structure have been characterized and discussed. From the characterizations, the hetero-structure has been successfully grown generally. However, due to the unintentional diffusion of Ga ions from Ga{sub 2}O{sub 3}/GaN layers, the most part of the nominal Fe{sub 3}O{sub 4} layer is actually in the form of Ga{sub x}Fe{sub 3−x}O{sub 4} with gradually decreased x values from the Fe{sub 3}O{sub 4}/Ga{sub 2}O{sub 3} interface to the Fe{sub 3}O{sub 4} surface. Post-annealing process can further aggravate the diffusion. Due to the similar ionic radius of Ga and Fe, the structural configuration of the Ga{sub x}Fe{sub 3−x}O{sub 4} does not differ from that of pure Fe{sub 3}O{sub 4}. However, the ferromagnetism has been reduced with the incorporation of Ga into Fe{sub 3}O{sub 4}, which has been explained by the increased Yafet-Kittel angles in presence of considerable amount of Ga incorporation. A different behavior of the magnetoresistance has been found on the as-grown and annealed samples, which could be modelled and explained by the competition between the spin-dependent and spin-independent conduction channels. This work has provided detailed information on the interfacial properties of the Fe{sub 3}O{sub 4}/Ga{sub 2}O{sub 3}/GaN spin injecting hetero-structure, which is the solid basis for further improvement and application of

Magnetic Properties and Microstructure of FeOx/Fe/FePt and FeOx/FePt Films

Directory of Open Access Journals (Sweden)

Jai-Lin Tsai

2013-01-01

Full Text Available The Fe(6 nm/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5~7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeOx(3 nm/Fe(3 nm/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeOx and Fe/FePt layers was decoupled. The moments in FeOx layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500°C and 800°C for 3 minutes. When the FeOx(3 nm/Fe(3 nm/FePt trilayer was annealed at 500°C, the layers structure was changed to FeOx(6 nm/FePt bilayer due to oxygen diffusion. The hard-magnetic FeOx(6 nm/FePt film was coupled with single switching field. The FeOx/(disordered FePt layer structure was observed with further annealing at 800°C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeOx layer, and hard-magnetic L10 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L10 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800°C.

Vapor deposition in basaltic stalactites, Kilauea, Hawaii

Science.gov (United States)

Baird, A. K.; Mohrig, D. C.; Welday, E. E.

Basaltic stalacties suspended from the ceiling of a large lava tube at Kilauea, Hawaii, have totally enclosed vesicles whose walls are covered with euhedral FeTi oxide and silicate crystals. The walls of the vesicles and the exterior surfaces of stalactites are Fe and Ti enriched and Si depleted compared to common basalt. Minerals in vesicles have surface ornamentations on crystal faces which include alkali-enriched, aluminosilicate glass(?) hemispheres. No sulfide-, chloride-, fluoride-, phosphate- or carbonate-bearing minerals are present. Minerals in the stalactites must have formed by deposition from an iron oxide-rich vapor phase produced by the partial melting and vaporization of wall rocks in the tube.

A simple method to deposit palladium doped SnO2 thin films using plasma enhanced chemical vapor deposition technique

International Nuclear Information System (INIS)

Kim, Young Soon; Wahab, Rizwan; Shin, Hyung-Shik; Ansari, S. G.; Ansari, Z. A.

2010-01-01

This work presents a simple method to deposit palladium doped tin oxide (SnO 2 ) thin films using modified plasma enhanced chemical vapor deposition as a function of deposition temperature at a radio frequency plasma power of 150 W. Stannic chloride (SnCl 4 ) was used as precursor and oxygen (O 2 , 100 SCCM) (SCCM denotes cubic centimeter per minute at STP) as reactant gas. Palladium hexafluroacetyleacetonate (Pd(C 5 HF 6 O 2 ) 2 ) was used as a precursor for palladium. Fine granular morphology was observed with tetragonal rutile structure. A peak related to Pd 2 Sn is observed, whose intensity increases slightly with deposition temperature. Electrical resistivity value decreased from 8.6 to 0.9 mΩ cm as a function of deposition temperature from 400 to 600 deg. C. Photoelectron peaks related to Sn 3d, Sn 3p3, Sn 4d, O 1s, and C 1s were detected with varying intensities as a function of deposition temperature.

Dense Fe cluster-assembled films by energetic cluster deposition

International Nuclear Information System (INIS)

Peng, D.L.; Yamada, H.; Hihara, T.; Uchida, T.; Sumiyama, K.

2004-01-01

High-density Fe cluster-assembled films were produced at room temperature by an energetic cluster deposition. Though cluster-assemblies are usually sooty and porous, the present Fe cluster-assembled films are lustrous and dense, revealing a soft magnetic behavior. Size-monodispersed Fe clusters with the mean cluster size d=9 nm were synthesized using a plasma-gas-condensation technique. Ionized clusters are accelerated electrically and deposited onto the substrate together with neutral clusters from the same cluster source. Packing fraction and saturation magnetic flux density increase rapidly and magnetic coercivity decreases remarkably with increasing acceleration voltage. The Fe cluster-assembled film obtained at the acceleration voltage of -20 kV has a packing fraction of 0.86±0.03, saturation magnetic flux density of 1.78±0.05 Wb/m 2 , and coercivity value smaller than 80 A/m. The resistivity at room temperature is ten times larger than that of bulk Fe metal

Plasma sprayed Nd-Fe-B permanent magnets

International Nuclear Information System (INIS)

Willson, M.; Bauser, S.; Liu, S.; Huang, M.

2003-01-01

This study demonstrated that the plasma spray deposition method is an alternative process for producing Nd-Fe-B magnets in addition to the two existing principal processes: the powder metallurgy process for producing sintered Nd-Fe-B magnets and the melt spinning process for bonded Nd-Fe-B magnets. Plasma spray is a potentially better process for producing magnetic parts with complicated shape, large area, thin thickness, small dimension, or unusual geometry. High intrinsic coercivity greater than 15 kOe was readily obtained for Nd 16 Dy 1 Fe 76 B 7 even in the as-deposited condition when the substrate was preheated. The plasma spray process contains only three steps: melting, crushing, and plasma spray, which is much simpler than the powder metallurgy and melt spinning processes. Without preheating the substrate, the coercivity was usually very low (∼0.1 kOe) in the as-deposited condition and it increased to 10 to >15 kOe after anneal. Evidence of magnetocrystalline anisotropy was observed in plasma sprayed Nd 15 Dy 1 Fe 77 B 7 magnets when the substrate was not preheated. It is believed that a crystal texture was developed during the plasma spray as a result of the existence of a temperature gradient in the solidifying melt

Magnetic properties and structure of FePt/FeMn multilayers

International Nuclear Information System (INIS)

Phuoc, Nguyen N.; Suzuki, Takao

2007-01-01

A systematic study of the magnetic properties by ion beam sputter-deposition system, was conducted in conjunction with the structure of FePt/FeMn multilayers fabricated onto MgO(0 0 1) substrates. Both parallel and perpendicular exchange biases were observed in the multilayers and were found to decrease drastically, as the deposition temperature is higher than 350 deg. C, which is evidently due to the interdiffusion at the interface. The thickness dependence study shows that the perpendicular magnetic anisotropy observed in the multilayers originates from surface anisotropy, being consistent with the decrease of perpendicular magnetic anisotropy as the deposition temperature is increased. The difference between parallel and perpendicular blocking temperatures that was clearly observed, is possibly due to the spin canting out of plane at the interface

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

Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

International Nuclear Information System (INIS)

Rao, Pratibha; Godbole, R.V.; Bhagwat, Sunita

2016-01-01

In this work, Pd:NiFe 2 O 4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe 2 O 4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost. - Highlights: • Ethanol gas sensors based on Pd:NiFe 2 O 4 nanoparticle thin film were fabricated. • Pd incorporation in NiFe 2 O 4 matrix inhibits grain growth. • The sensors were more selective to ethanol gas. • Sensors exhibited fast response and recovery when doped with palladium. • Pd:NiFe 2 O 4 thin film sensor displays excellent long–term stability.

Structural study of U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 at high pressure

CERN Document Server

Sikolenko, V V; Pomjakushina, E V; Pomjakushin, V Y; Balagurov, A M; Keller, L; Glazkov, V P; Gribanov, A V; Goncharenko, I N; Savenko, B N

2003-01-01

The crystal structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with Fe content x = 0- 0.03 and the crystal and magnetic structure of U(Pd sub 0 sub . sub 9 sub 8 Fe sub 0 sub . sub 0 sub 2) sub 2 Ge sub 2 at high external pressures up to 4.5 GPa were studied by means of powder neutron diffraction in the temperature range 1.5-300 K. With increasing Fe content the values of the lattice parameters and interatomic distances change only slightly, but it is known from previous experiments that the magnetic structure changes drastically for x >= 0.015. In contrast to this, high external pressure modifies the crystal structure more significantly while the magnetic structure remains unchanged. The results obtained allow one to infer that drastic changes in the magnetic structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with increasing Fe content are a consequence of modification of the RKKY-type (RKKY standing for Ruderman, Kittel, Kasuya and Yosida) indirect exchange in...

Structural features of epitaxial NiFe2O4 thin films grown on different substrates by direct liquid injection chemical vapor deposition

Science.gov (United States)

Datta, R.; Loukya, B.; Li, N.; Gupta, A.

2012-04-01

NiFe2O4 (NFO) thin films are grown on four different substrates, i.e., Lead Zinc Niobate-Lead Titanate (PZN-PT), Lead Magnesium Niobate-Lead Titanate (PMN-PT), MgAl2O4 (MAO) and SrTiO3 (STO), by a direct liquid injection chemical vapor deposition technique (DLI-CVD) under optimum growth conditions where relatively high growth rate (˜20 nm/min), smooth surface morphology and high saturation magnetization values in the range of 260-290 emu/ cm3 are obtained. The NFO films with correct stoichiometry (Ni:Fe=1:2) grow epitaxially on all four substrates, as confirmed by energy dispersive X-ray spectroscopy, transmission electron microscopy and x-ray diffraction. While the films on PMN-PT and PZN-PT substrates are partially strained, essentially complete strain relaxation occurs for films grown on MAO and STO. The formations of threading dislocations along with dark diffused contrast areas related to antiphase domains having a different cation ordering are observed on all four substrates. These crystal defects are correlated with lattice mismatch between the film and substrate and result in changes in magnetic properties of the films. Atomic resolution HAADF imaging and EDX line profiles show formation of a sharp interface between the film and the substrate with no inter-diffusion of Pb or other elements across the interface. Antiphase domains are observed to originate at the film-substrate interface.

Photoelectrochemical energy conversion obtained with ultrathin organo-metallic-chemical-vapor-deposition layer of FeS2 (pyrite) on TiO2

International Nuclear Information System (INIS)

Ennaoui, A.; Fiechter, S.; Tributsch, H.; Giersig, M.; Vogel, R.; Weller, H.

1992-01-01

Ultrathin (10 to 20 nm thick), polycrystalline films of FeS 2 (pyrite) were grown on TiO 2 (anatase) by chemical vapor deposition. The FeS 2 films were characterized using optical absorption and high-resolution electron microscopy. Photoelectrochemical solar cells, using TiO 2 (anatase) coated with FeS 2 ultrathin films, generated high open-circuit photo-voltages, of up to 600 mV, compared with a single crystal of pyrite electrode (200 mV). The photoelectrochemical behavior shows a strong dependence of photovoltage and photocurrent on the pH of the solution. This paper reports that it is explained by electron injection from the conduction band of FeS 2 to the conduction band of TiO 2 . Regeneration of holes is taking place by electron transfer from the redox system in the electrolyte

Structural and magnetic properties of granular CoPd multilayers

Science.gov (United States)

Vivas, L. G.; Figueroa, A. I.; Bartolomé, F.; Rubín, J.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Brookes, N. B.; Wilhelm, F.; Rogalev, A.; Bartolomé, J.

2016-02-01

Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk.

Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

International Nuclear Information System (INIS)

Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

2017-01-01

We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi_3Fe_5O_1_2, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi_3Fe_5O_1_2 was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi_3Fe_5O_1_2. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe"3"+ ions.

Effect of non-magnetic intermediate layer on film structure, magnetic properties, and noise characteristics of FeCSi soft magnetic multilayers

International Nuclear Information System (INIS)

Kawano, Hiroyasu; Morikawa, Takeshi; Matsumoto, Koji; Shono, Keiji

2004-01-01

The film structures, magnetic properties, and noise characteristics of soft magnetic multilayers with alternately stacked FeCSi soft magnetic layers and non-magnetic intermediate layers were investigated. The FeCSi layers in an as-deposited multilayer with C or Ta intermediate layers had the same nano-sized fine crystalline grains and low media noise as an as-deposited FeCSi monolayer. Amorphous C intermediate layers suppressed the amplitude of spike noise especially well. In contrast, FeCSi layers in an as-deposited multilayer with Cr or Ti intermediate layers were composed of coarse crystalline grains, which increased the media noise. The crystallographic match at the interface between the layers in a multilayer could explain these phenomena. The similarity of the atomic arrangement at the interface between layers and the crystallographic match of less than a few percent for the distance between atoms crystallized FeCSi layers with nano-sized fine crystalline grains into ones with coarse crystalline grains during deposition

Uniaxial Magnetization Performance of Textured Fe Nanowire Arrays Electrodeposited by a Pulsed Potential Deposition Technique

Science.gov (United States)

Neetzel, C.; Ohgai, T.; Yanai, T.; Nakano, M.; Fukunaga, H.

2017-11-01

Textured ferromagnetic Fe nanowire arrays were electrodeposited using a rectangular-pulsed potential deposition technique into anodized aluminum oxide nanochannels. During the electrodeposition of Fe nanowire arrays at a cathodic potential of - 1.2 V, the growth rate of the nanowires was ca. 200 nm s-1. The aspect ratio of Fe nanowires with a diameter of 30 ± 5 nm reached ca. 2000. The long axis of Fe nanowires corresponded with the direction when a large overpotential during the on-time pulse was applied, whereas it orientated to the direction under the potentiostatic condition with a small overpotential. By shifting the on-time cathode potential up to - 1.8 V, the texture coefficient for the (200) plane, TC200, reached up to 1.94. Perpendicular magnetization performance was observed in Fe nanowire arrays. With increasing TC200, the squareness of Fe nanowire arrays increased up to 0.95 with the coercivity maintained at 1.4 kOe at room temperature. This research result has opened a novel possibility of Fe nanowire arrays that can be applied for a new permanent magnetic material without rare-earth metals.

A simple way to prepare reduced graphene oxide nanosheets/Fe2O3-Pd/N-doped carbon nanosheets and their application in catalysis.

Science.gov (United States)

Yao, Tongjie; Zhang, Junshuai; Zuo, Quan; Wang, Hao; Wu, Jie; Zhang, Xiao; Cui, Tieyu

2016-04-15

The catalysts with Pd and γ-Fe2O3 nanoparticles embedded between reduced graphene oxide nanosheets (rGS) and N-doped carbon nanosheets (NCS) were prepared through a two-step method. Firstly, graphene oxide nanosheets (GS)/prussian blue (PB)-Pd/polypyrrole (PPy) composites were synthesized by using pyrrole monomer as reductant, K3Fe(CN)6 and PdCl2 as oxidants in the presence of GS via a redox reaction. Subsequently, the as-obtained GS/PB-Pd/PPy composites were calcinated in N2 atmosphere. During the heat-treatment, carbonization of PPy to NCS, conversion of nonmagnetic PB to magnetic γ-Fe2O3 nanoparticles, and reduction of GS to rGS were finished, simultaneously. rGS/Fe2O3-Pd/NCS composites exhibited good catalytic activity toward reduction of 4-nitrophenol. The rate constant k and turnover frequency were calculated and compared with recent reports. Owing to γ-Fe2O3 nanoparticles, the rGS/Fe2O3-Pd/NCS composites could be quickly separated by magnet and reused without obvious decrease in activity. Copyright © 2016 Elsevier Inc. All rights reserved.

Vapor deposition of tantalum and tantalum compounds

International Nuclear Information System (INIS)

Trkula, M.

1996-01-01

Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition

Annealing and thickness effects on magnetic properties of Co2FeAl alloy films

Science.gov (United States)

Wang, Ke; Xu, Zhan; Ling, Fujin; Wang, Yahong; Dong, Shuo

2018-03-01

Co2FeAl (CFA) films in a wide thickness range between 2 and 100 nm are sputtered at room temperature. Perpendicular magnetic anisotropy (PMA) is achieved in the annealed structure of Pd/CFA/MgO with CFA thickness ranging between 2.3 and 4.9 nm. PMA as high as 2 × 106 erg/cm3 is demonstrated in the structures annealed in the temperature range between 300 and 350 °C. Positive contributions to the PMA made by the interfaces of Pd/CFA and CFA/MgO are identified. For the as-deposited structure of MgO/CFA/Ta with thick CFA alloy up to 5 nm or above a high effective saturation magnetization of 983.9 ± 30.1 emu/cc is derived from the fitting and an in-plane uniaxial magnetic anisotropy of 104 erg/cm3 in magnitude is revealed by angular dependent magnetic measurements. In addition to the increase in saturation magnetization, a fourfold cubic magnetic anisotropy is found to develop with annealing, in line with the improvement of the crystalline structure confirmed by X-ray diffraction measurements. Out results provide some useful information for the design of the CFA-based magnetoelectronic devices.

Spin pumping damping and magnetic proximity effect in Pd and Pt spin-sink layers

Science.gov (United States)

Caminale, M.; Ghosh, A.; Auffret, S.; Ebels, U.; Ollefs, K.; Wilhelm, F.; Rogalev, A.; Bailey, W. E.

2016-07-01

We investigated the spin pumping damping contributed by paramagnetic layers (Pd, Pt) in both direct and indirect contact with ferromagnetic Ni81Fe19 films. We find a nearly linear dependence of the interface-related Gilbert damping enhancement Δ α on the heavy-metal spin-sink layer thicknesses tN in direct-contact Ni81Fe19 /(Pd, Pt) junctions, whereas an exponential dependence is observed when Ni81Fe19 and (Pd, Pt) are separated by 3 nm Cu. We attribute the quasilinear thickness dependence to the presence of induced moments in Pt, Pd near the interface with Ni81Fe19 , quantified using x-ray magnetic circular dichroism measurements. Our results show that the scattering of pure spin current is configuration-dependent in these systems and cannot be described by a single characteristic length.

Tuning high frequency magnetic properties and damping of FeGa, FeGaN and FeGaB thin films

Directory of Open Access Journals (Sweden)

Derang Cao

2017-11-01

Full Text Available A series of FeGa, FeGaN and FeGaB films with varied oblique angles were deposited by sputtering method on silicon substrates, respectively. The microstructure, soft magnetism, microwave properties, and damping factor for the films were investigated. The FeGa films showed a poor high frequency magnetic property due to the large stress itself. The grain size of FeGa films was reduced by the additional N element, while the structure of FeGa films was changed from the polycrystalline to amorphous phase by the involved B element. As a result, N content can effectively improve the magnetic softness of FeGa film, but their high frequency magnetic properties were still poor both when the N2/Ar flow rate ratio is 2% and 5% during the deposition. The additional B content significantly led to the excellent magnetic softness and the self-biased ferromagnetic resonance frequency of 1.83 GHz for FeGaB film. The dampings of FeGa films were adjusted by the additional N and B contents from 0.218 to 0.139 and 0.023, respectively. The combination of these properties for FeGa films are helpful for the development of magnetostrictive microwave devices.

PPARα, PPARγ and SREBP-1 pathways mediated waterborne iron (Fe)-induced reduction in hepatic lipid deposition of javelin goby Synechogobius hasta.

Science.gov (United States)

Chen, Guang-Hui; Luo, Zhi; Chen, Feng; Shi, Xi; Song, Yu-Feng; You, Wen-Jing; Liu, Xu

2017-07-01

The 42-day experiment was conducted to investigate the effects and mechanism of waterborne Fe exposure influencing hepatic lipid deposition in Synechogobius hasta. For that purpose, S. hasta were exposed to four Fe concentrations (0 (control), 0.36, 0.72 and 1.07μM Fe) for 42days. On days 21 and 42, morphological parameters, hepatic lipid deposition and Fe contents, and activities and mRNA levels of enzymes and genes related to lipid metabolism, including lipogenic enzymes (6PGD, G6PD, ME, ICDH, FAS and ACC) and lipolytic enzymes (CPTI, HSL), were analyzed. With the increase of Fe concentration, hepatic Fe content tended to increase but HSI and lipid content tended to decrease. On day 21, Fe exposure down-regulated the lipogenic activities of 6PGD, G6PD, ICDH and FAS as well as the mRNA levels of G6PD, ACCa, FAS, SREBP-1 and PPARγ, but up-regulated CPT I, HSLa and PPARα mRNA levels. On day 42, Fe exposure down-regulated the lipogenic activities of 6PGD, G6PD, ICDH and FAS as well as the mRNA levels of 6PGD, ACCa, FAS and SREBP-1, but up-regulated CPT I, HSLa, PPARα and PPARγ mRNA levels. Using primary S. hasta hepatocytes, specific pathway inhibitors (GW6471 for PPARα and fatostatin for SREBP-1) and activator (troglitazone for PPARγ) were used to explore the signaling pathways of Fe reducing lipid deposition. The GW6471 attenuated the Fe-induced down-regulation of mRNA levels of 6PGD, G6PD, ME, FAS and ACCa, and attenuated the Fe-induced up-regulation of mRNA levels of CPT I, HSLa and PPARα. Compared with single Fe-incubated group, the mRNA levels of G6PD, ME, FAS, ACCa, ACCb and PPARγ were up-regulated while the CPT I mRNA levels were down-regulated after troglitazone pre-treatment; fatostatin pre-treatment down-regulated the mRNA levels of 6PGD, ME, FAS, ACCa, ACCb and SREBP-1, and increased the CPT I and HSLa mRNA levels. Based on these results above, our study indicated that Fe exposure reduced hepatic lipid deposition by down-regulating lipogenesis

Magnetic properties of {alpha}-Fe and Fe{sub 3}C nanowires

Energy Technology Data Exchange (ETDEWEB)

Lutz, M U; Weissker, U; Wolny, F; Mueller, C; Loeffler, M; Muehl, T; Leonhardt, A; Buechner, B; Klingeler, R, E-mail: m.lutz@ifw-dresden.d [Leibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany)

2010-01-01

The magnetic properties of single domain {alpha}-Fe and Fe{sub 3}C nanowires encapsulated within Multi Walled Carbon Nanotubes (MWNT) are investigated with a Magnetic Force Microscope (MFM). The wires are formed during the Chemical Vapour Deposition growth process, partially filling the hollow center of the MWNTs. The wires have a diameter variation of 10-60nm and can be several {mu}m long. The phase and crystal orientation of the filling relative to the long tube axis are probed by Transmission Electron Microscopy. The remanent magnetization states of the wires are investigated by MFM imaging. The {alpha}-Fe wires show shape dominated magnetization along the tube axis, whereas the FesC wires show a perpendicular magnetization imposed by magneto-crystalline anisotropy. Switching fields of {alpha}-Fe nanowires are determined by the application of an in-situ magnetic field, revealing a tip triggered magnetization reversal by localized nucleation.

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

Directory of Open Access Journals (Sweden)

Claudia Espro

2017-03-01

Full Text Available This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C–C and C–O cleavage of platform molecules such as C2–C6 polyols, furfural, phenol derivatives and aromatic ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components of lignocellulosic biomasses. The interaction between palladium and iron affords bimetallic Pd-Fe sites (ensemble or alloy that were found to be very active in several sustainable reactions including hydrogenolysis, catalytic transfer hydrogenolysis (CTH and aqueous phase reforming (APR that will be highlighted. This contribution concentrates also on the different synthetic strategies (incipient wetness impregnation, deposition-precipitaion, co-precipitaion adopted for the preparation of heterogeneous Pd-Fe systems as well as on the main characterization techniques used (XRD, TEM, H2-TPR, XPS and EXAFS in order to elucidate the key factors that influence the unique catalytic performances observed.

Influence of deposition field on the magnetic anisotropy in epitaxial Co70Fe30 films on GaAs(001)

International Nuclear Information System (INIS)

Hindmarch, A.T.; Arena, D.; Dempsey, K.J.; Henini, M.; Marrows, C.H.

2010-01-01

The effect of the application of a magnetic field during deposition of epitaxial Co 70 Fe 30 onto GaAs(001) is shown; we find an initially counterintuitive result. For field applied along the interfacial uniaxial hard axis the relative effective uniaxial magnetic anisotropy is increased by a factor of two in comparison to both field along the uniaxial easy axis, or no field; usually, application of a deposition field results in a uniaxial easy axis parallel to this field direction. We show that the deposition field changes the maximal projection of the atomic orbital magnetic moments onto the easy axis, which corresponds to a deposition field induced shift in the Helmholtz free-energy landscape of the system.

Convenient synthesis of magnetically recyclable Fe{sub 3}O{sub 4}@C@CdS photocatalysts by depositing CdS nanocrystals on carbonized ferrocene

Energy Technology Data Exchange (ETDEWEB)

Li, Dan [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Xie, Jianjian [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Zhang, Yong; Qiao, Ru [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Sheng [Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Li, Zhengquan, E-mail: zqli@zjnu.edu.cn [Institute of Physical Chemistry, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China); Department of Materials Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004 (China)

2015-10-15

Development of magnetic visible-light-driven photocatalysts is desirable to the practical application of photocatalyts for collection and recycling use. Here we present a facile approach to synthesize Fe{sub 3}O{sub 4}@C@CdS magnetic photocatalysts which can avoid multi-step preparation process. Through one-step solvothermal carbonization of ferrocene, the produced carbon-coated Fe{sub 3}O{sub 4} clusters can serve as both magnetic cores and deposition substrates for in situ generating crystalline CdS nanocrystals on them by rapid microwave irradiation. The prepared Fe{sub 3}O{sub 4}@C@CdS nanoparticles exhibit a uniform core–shell structure and display good photocatalytic activity and recyclability in the degradation of organic dyes. These magnetic photocatalysts may find potential application in wastewater treatment for the future environment remedy. - Highlights: • A rapid strategy is presented to obtain multifunctional core–shell nanostructures. • Magnetic visible-light-driven Fe{sub 3}O{sub 4}@C@CdS nanophotocatalysts are synthesized. • Carbonized ferrocene can provide both magnetic cores and good deposition substrate. • Photocatalytic and recyclable properties of Fe{sub 3}O{sub 4}@C@CdS nanoparticles are explored.

Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives

Directory of Open Access Journals (Sweden)

Cai Liang

2014-07-01

Full Text Available This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B.

Magnetic properties of FeNi-based thin film materials with different additives

KAUST Repository

Liang, C.

2014-07-04

This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. 2014 by the authors.

Poly(o-phenylenediamine)/NiCoFe{sub 2}O{sub 4} nanocomposites: Synthesis, characterization, magnetic and dielectric properties

Energy Technology Data Exchange (ETDEWEB)

Kannapiran, Nagarajan [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India); Muthusamy, Athianna, E-mail: muthusrkv@gmail.com [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India); Chitra, Palanisamy; Anand, Siddeswaran [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India); Jayaprakash, Rajan [Nanotechnology Laboratory, Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India)

2017-02-01

In this study, poly(o-phenylenediamine) (PoPD)/NiCoFe{sub 2}O{sub 4} nanocomposites were synthesized by in-situ oxidative chemical polymerization method with different amount of NiCoFe{sub 2}O{sub 4} nanoparticles. The NiCoFe{sub 2}O{sub 4} nanoparticles were prepared by auto-combustion method. The structural, morphological, thermal properties of the synthesized PoPD/NiCoFe{sub 2}O{sub 4} nanocomposites were characterized by fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Magnetic properties of NiCoFe{sub 2}O{sub 4} nanoparticles and PoPD/NiCoFe{sub 2}O{sub 4} nanocomposites were studied by vibrating sample magnetometer (VSM). The FTIR and XRD techniques were used to confirm the formation of PoPD/NiCoFe{sub 2}O{sub 4} nanocomposites. The average crystalline size of NiCoFe{sub 2}O{sub 4} nanoparticles and PoPD/NiCoFe{sub 2}O{sub 4} nanocomposites were calculated from XRD. From the SEM analysis, spherical morphology of the PoPD was confirmed. The TGA results showed that the NiCoFe{sub 2}O{sub 4} nanoparticles have improved the thermal stability of PoPD. Dielectric properties of PoPD/NiCoFe{sub 2}O{sub 4} nanocomposites at different temperatures have been carried in the frequency range 50 Hz to 5 MHz. - Highlights: • Auto-combustion method was support to achieve less particle size. • Green synthesis of PoPD and nanocomposites by in-situ oxidative chemical polymerization method. • For the first time, PoPD incorporated with NiCoFe{sub 2}O{sub 4} nanoparticles. • Ferrite content affects the magnetic and dielectric properties of the nanocomposites.

Ion vapor deposition and its application

International Nuclear Information System (INIS)

Bollinger, H.; Schulze, D.; Wilberg, R.

1981-01-01

Proceeding from the fundamentals of ion vapor deposition the characteristic properties of ion-plated coatings are briefly discussed. Examples are presented of successful applications of ion-plated coatings such as coatings with special electrical and dielectric properties, coatings for corrosion prevention, and coatings for improving the surface properties. It is concluded that ion vapor deposition is an advantageous procedure in addition to vapor deposition. (author)

PLD growth of CoPd thin films and characterization of their magnetic properties by magneto optical Kerr effect

Science.gov (United States)

Sedrpooshan, Mehran; Ahmadvand, Hossein; Ranjbar, Mehdi; Salamati, Hadi

2018-06-01

CoPd alloy thin films with different thicknesses and Co/Pd ratios have been deposited on Si (100) substrate by pulsed laser deposition (PLD). The magnetic properties were investigated by using the magneto-optical Kerr effect (MOKE) in both longitudinal and polar geometries. The results show that the films with thickness in the range of 6-24 nm, deposited at a low substrate temperature of 200 °C, are mostly magnetized in the plane of film. Higher deposition temperature forces the magnetic easy axis to orient in the perpendicular direction of the films.

Preparation of ultrafine iron particles by chemical vapor deposition of Fe(CO) sub 5. Fe(CO) sub 5 wo gebryo to suru kiso kagaku hanno ni yoru tetsuchobiryushi no seisei

Energy Technology Data Exchange (ETDEWEB)

Sawada, Y; Kageyama, Y. (Mitsubishi Petrochemical Co. Ltd., Tokyo (Japan)): Iwata, M. (Nagoya University, Nagoya (Japan). Faculty of Engineering)

1991-11-10

An ultrafine iron particle preparing process was developed, which wses gaseous phase pyrolysis in magnetic field of iron pentacarbonyl, Fe(CO){sub 5}, based on the fact that Fe(CO){sub 5} has peculiar characters that its boiling point is as low as 103{degree}C, and starts decomposing in a low temperature zone of 100{degree}C or lower. Vaporizing and introducing into a reactor an fe(CO){sub 5}, andPyrolyzing it at 200-600{degree}C while being diluted with nitrogen and applied with a magnetic field produced uitrafine iron particles of a necklace-like chain comprisinh primary particles having diameter of 15 to 25 nm with 10 to 40 of them linked in a straight chain. It was found that the specific surface area is 30-50 m{sup 2}/g, with the diameter converted from the specific surface area being relatively close to the average diameter obtained from TEM photograph, and that the particle has few pores. Magnetically the iron powder has a coercivity of 123-131 KA/m and a specific saturation magnetization of 120-140 Am{sup 2}/kg, and is expected to be applied as a high density magnetic recording medium. 5 refs.,8 figs., 3 tabs.

Facile Fabrication of Highly Active Magnetic Aminoclay Supported Palladium Nanoparticles for the Room Temperature Catalytic Reduction of Nitrophenol and Nitroanilines

Directory of Open Access Journals (Sweden)

Lei Jia

2018-06-01

Full Text Available Magnetically recyclable nanocatalysts with excellent performance are urgent need in heterogeneous catalysis, due to their magnetic nature, which allows for convenient and efficient separation with the help of an external magnetic field. In this research, we developed a simple and rapid method to fabricate a magnetic aminoclay (AC based an AC@Fe3O4@Pd nanocatalyst by depositing palladium nanoparticles (Pd NPs on the surface of the magnetic aminoclay nanocomposite. The microstructure and the magnetic properties of as-prepared AC@Fe3O4@Pd were tested using transmission electron microscopy (TEM, energy-dispersive X-ray spectroscopy (EDS, X-ray diffraction (XRD, and vibrating sample magnetometry (VSM analyses. The resultant AC@Fe3O4@Pd nanocatalyst with the magnetic Fe-based inner shell, catalytically activate the outer noble metal shell, which when combined with ultrafine Pd NPs, synergistically enhanced the catalytic activity and recyclability in organocatalysis. As the aminoclay displayed good water dispersibility, the nanocatalyst indicated satisfactory catalytic performance in the reaction of reducing nitrophenol and nitroanilines to the corresponding aminobenzene derivatives. Meanwhile, the AC@Fe3O4@Pd nanocatalyst exhibited excellent reusability, while still maintaining good activity after several catalytic cycles.

Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

Energy Technology Data Exchange (ETDEWEB)

Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa, E-mail: tanaka@dipole7.kuic.kyoto-u.ac.jp

2017-01-15

We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi{sub 3}Fe{sub 5}O{sub 12}, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi{sub 3}Fe{sub 5}O{sub 12} was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi{sub 3}Fe{sub 5}O{sub 12}. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe{sup 3+} ions.

Interfacial magnetic coupling between Fe nanoparticles in Fe–Ag granular alloys

International Nuclear Information System (INIS)

Alonso, J; Fdez-Gubieda, M L; Sarmiento, G; Chaboy, J; Boada, R; García Prieto, A; Haskel, D; Laguna-Marco, M A; Lang, J C; Meneghini, C; Fernández Barquín, L; Neisius, T; Orue, I

2012-01-01

The role of the interface in mediating interparticle magnetic interactions has been analysed in Fe 50 Ag 50 and Fe 55 Ag 45 granular thin films deposited by the pulsed laser deposition technique (PLD). These samples are composed of crystalline bcc Fe (2–4 nm) nanoparticles and fcc Ag (10–12 nm) nanoparticles, separated by an amorphous Fe 50 Ag 50 interface, occupying around 20% of the sample volume, as determined by x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), and high resolution transmission electron microscopy (HRTEM). Interfacial magnetic coupling between Fe nanoparticles is studied by dc magnetization and x-ray magnetic circular dichroism (XMCD) measurements at the Fe K and Ag L 2,3 edges. This paper reveals that these thin films present two magnetic transitions, at low and high temperatures, which are strongly related to the magnetic state of the amorphous interface, which acts as a barrier for interparticle magnetic coupling.

Thin films of NdFeB deposited by PLD technique

International Nuclear Information System (INIS)

Constantinescu, C.; Scarisoreanu, N.; Moldovan, A.; Dinescu, M.; Petrescu, L.; Epureanu, G.

2007-01-01

Neodymium-iron-boron (NdFeB) is a material with important magnetic properties, mostly used in permanent magnet fabrication. Thin layers of NdFeB are needed for miniaturization in electrical engineering, electronics and for high-tech devices. In this paper we applied pulsed lased deposition (PLD) in vacuum for obtaining thin films of NdFeB from stoichiometric targets. The influence of different buffer layers and of the laser parameters (wavelength and fluence) on the NdFeB structures, composition and magnetic properties have been investigated. The obtained structures were characterized by atomic force microscopy (AFM) and optical microscopy. Vibrating sample magnetometry (VSM) has been performed for specific magnetic characterization

Thin films of NdFeB deposited by PLD technique

Energy Technology Data Exchange (ETDEWEB)

Constantinescu, C. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Scarisoreanu, N. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Moldovan, A. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Dinescu, M. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania)]. E-mail: dinescum@ifin.nipne.ro; Petrescu, L. [Department of Electrical Engineering, ' Politehnica' University of Bucharest, 313 Spl. Independentei, 060042 Bucharest (Romania); Epureanu, G. [Department of Electrical Engineering, ' Politehnica' University of Bucharest, 313 Spl. Independentei, 060042 Bucharest (Romania)

2007-07-31

Neodymium-iron-boron (NdFeB) is a material with important magnetic properties, mostly used in permanent magnet fabrication. Thin layers of NdFeB are needed for miniaturization in electrical engineering, electronics and for high-tech devices. In this paper we applied pulsed lased deposition (PLD) in vacuum for obtaining thin films of NdFeB from stoichiometric targets. The influence of different buffer layers and of the laser parameters (wavelength and fluence) on the NdFeB structures, composition and magnetic properties have been investigated. The obtained structures were characterized by atomic force microscopy (AFM) and optical microscopy. Vibrating sample magnetometry (VSM) has been performed for specific magnetic characterization.

Ultra-low Pt decorated PdFe Alloy Nanoparticles for Formic Acid Electro-oxidation

International Nuclear Information System (INIS)

Zhou, Yawei; Du, Chunyu; Han, Guokang; Gao, Yunzhi; Yin, Geping

2016-01-01

Highlights: • A cost-efficient way is used to prepare transition-noble metal alloy nanoparticles. • The Pd 50 Fe 50 /C catalyst shows excellent activity for formic acid oxidation (FAO). • Much activity enhancement of FAO is acquired by ultra-low Pt decorated Pd 50 Fe 50 . • A synergistic mechanism between Pt clusters and PdFe is proposed during the FAO. - Abstract: Palladium (Pd), has demonstrated promising electro-catalytic activity for formic acid oxidation, but suffers from extremely low abundance. Recently alloying with a transition metal has been considered as an effective approach to reducing the loading of Pd and enhancing the activity of Pd-based catalysts simultaneously. Herein, carbon supported PdFe nanoparticles (NPs) are synthesized at room temperature by using sodium borohydride as reducing agent and potassium ferrocyanide as Fe precursor. The Pd 50 Fe 50 alloy sample annealed at 900 °C for 1 h shows the best catalytic activity among Pd x Fe 1-x (x = 0.2, 0.4, 0.5, 0.6, and 0.8) towards formic acid oxidation. To further improve both catalytic activity and stability, the ultra-low Pt (0.09 wt %) decorated Pd 50 Fe 50 NPs (PtPd/PdFe) are prepared via the galvanic replacement reaction. Compared with Pd 50 Fe 50 /C, the PtPd/PdFe/C Exhibits 1.52 times higher catalytic activity and lower onset potential (−0.12 V). The significant enhancements of formic acid oxidation can be attributed to the accelerated dehydrogenation reaction of formic acid by Pt atomic clusters. Moreover, the PtPd/PdFe/C also demonstrates better tolerance to poisons during formic acid oxidation.

Vaporization thermodynamics of Pd-rich intermediate phases in the Pd–Yb system

Energy Technology Data Exchange (ETDEWEB)

Ciccioli, A., E-mail: andrea.ciccioli@uniroma1.it [Dipartimento di Chimica, Sapienza Università di Roma, p.le Aldo Moro 5, 00185 Roma (Italy); Balducci, G.; Gigli, G. [Dipartimento di Chimica, Sapienza Università di Roma, p.le Aldo Moro 5, 00185 Roma (Italy); Provino, A. [Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, via Dodecaneso 31, 16146 Genova (Italy); Istituto SPIN-CNR, Corso Perrone 24, 16152 Genova (Italy); Palenzona, A. [Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, via Dodecaneso 31, 16146 Genova (Italy); Manfrinetti, P. [Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, via Dodecaneso 31, 16146 Genova (Italy); Istituto SPIN-CNR, Corso Perrone 24, 16152 Genova (Italy)

2016-02-20

Highlights: • Vaporization equilibria of Pd–Yb intermediate phases investigated by effusion techniques. • Heats of formation of Pd–Yb compounds determined from decomposition/atomization enthalpies. • Phase diagram of the Pd–Yb system re-drawn. • Influence of the Yb valence state on the thermodynamic properties observed. - Abstract: The vaporization thermodynamics of several intermediate phases in the Pd–Yb system was investigated by means of vaporization experiments performed under Knudsen conditions (KEML, Knudsen Effusion Mass Loss). The following thermal decomposition processes were studied in the overall temperature range 819–1240 K and their enthalpy changes determined: 4 PdYb(s) = Pd{sub 4}Yb{sub 3}(s) + Yb(g); 5/3 Pd{sub 4}Yb{sub 3}(s) = 4/3 Pd{sub 5}Yb{sub 3}(s) + Yb(g); 21/13 Pd{sub 5}Yb{sub 3}(s) = 5/13 Pd{sub 21}Yb{sub 10}(s) + Yb(g); 1/3 Pd{sub 21}Yb{sub 10}(s) = 21/9 Pd{sub 3}Yb(s) + Yb(g). Additional measurements were performed by KEMS (Knudsen Effusion Mass Spectrometry) on a Pd-rich two-phase sample, which allowed to detect both Yb(g) and Pd(g) in the vapor phase and to determine the atomization enthalpy of the Pd{sub 3}Yb phase (Pd-rich composition boundary, Pd{sub 3.08}Yb{sub 0.92}): Pd{sub 3.08}Yb{sub 0.92}(s) = 0.92 Yb(g) + 3.08 Pd(g). The enthalpy of formation of this compound was thereafter determined as −68 ± 2 kJ/mol at. and, by combining this value with the decomposition enthalpies derived by KEML, the enthalpies of formation of the studied Pd–Yb intermediate phases were evaluated (kJ/mol at.): −75 ± 4 (Pd{sub 21}Yb{sub 10}), −75 ± 3 (Pd{sub 5}Yb{sub 3}), −73 ± 3 (Pd{sub 4}Yb{sub 3}), and −66 ± 3 (PdYb). A modified version of the Pd–Yb phase diagram is also reported, re-drawn on the basis of literature data and of new experimental information recently become available.

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.

Soft magnetic properties of hybrid ferromagnetic films with CoFe, NiFe, and NiFeCuMo layers

Energy Technology Data Exchange (ETDEWEB)

Choi, Jong-Gu [Eastern-western Biomedical Engineering, Sangji University, Wonju 220-702 (Korea, Republic of); Hwang, Do-Guwn [Dept. of Oriental Biomedical Engineering, Sangji University, Wonju 220-702 (Korea, Republic of); Rhee, Jang-Roh [Dept. of Physics, Sookmyung Women' s University, Seoul 140-742 (Korea, Republic of); Lee, Sang-Suk, E-mail: sslee@sangji.ac.kr [Dept. of Oriental Biomedical Engineering, Sangji University, Wonju 220-702 (Korea, Republic of)

2011-09-30

Two-layered ferromagnetic alloy films (NiFe and CoFe) with intermediate NiFeCuMo soft magnetic layers of different thicknesses were investigated to understand the relationship between coercivity and magnetization process by taking into account the strength of hard-axis saturation field. The thickness dependence of H{sub EC} (easy-axis coercivity), H{sub HS} (hard-axis saturation field), and {chi} (susceptibility) of the NiFeCuMo thin films in glass/Ta(5 nm)/[CoFe or NiFe(5 nm-t/2)]/NiFeCuMo(t = 0, 4, 6, 8, 10 nm)/[CoFe or NiFe(5 nm-t/2)]/Ta(5 nm) films prepared using the ion beam deposition method was determined. The magnetic properties (H{sub EC}, H{sub HS}, and {chi}) of the ferromagnetic CoFe, NiFe three-layers with an intermediate NiFeCuMo super-soft magnetic layer were strongly dependent on the thickness of the NiFeCuMo layer.

Pd-isatin Schiff base complex immobilized onγ-Fe2O3 as a magnetically recyclable catalyst for the Heck and Suzuki cross-coupling reactions

Institute of Scientific and Technical Information of China (English)

Sara Sobhani; Farzaneh Zarifi

2015-01-01

A Pd‐isatin Schiff base complex immobilized onγ‐Fe2O3 (Pd‐isatin Schiff base‐γ‐Fe2O3) was synthe‐sized and characterized by Fourier transform infrared, scanning electron microscopy, high resolu‐tion transmission electron microscopy, X‐ray diffraction, thermogravimetric gravimetric analysis, inductively‐coupled plasma, X‐ray photoelectron spectroscopy, and elemental analysis. It was used as a magnetically reusable Pd catalyst for the Heck and Suzuki cross‐coupling reactions.

Poly(o-phenylenediamine)/NiCoFe2O4 nanocomposites: Synthesis, characterization, magnetic and dielectric properties

Science.gov (United States)

Kannapiran, Nagarajan; Muthusamy, Athianna; Chitra, Palanisamy; Anand, Siddeswaran; Jayaprakash, Rajan

2017-02-01

In this study, poly(o-phenylenediamine) (PoPD)/NiCoFe2O4 nanocomposites were synthesized by in-situ oxidative chemical polymerization method with different amount of NiCoFe2O4 nanoparticles. The NiCoFe2O4 nanoparticles were prepared by auto-combustion method. The structural, morphological, thermal properties of the synthesized PoPD/NiCoFe2O4 nanocomposites were characterized by fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Magnetic properties of NiCoFe2O4 nanoparticles and PoPD/NiCoFe2O4 nanocomposites were studied by vibrating sample magnetometer (VSM). The FTIR and XRD techniques were used to confirm the formation of PoPD/NiCoFe2O4 nanocomposites. The average crystalline size of NiCoFe2O4 nanoparticles and PoPD/NiCoFe2O4 nanocomposites were calculated from XRD. From the SEM analysis, spherical morphology of the PoPD was confirmed. The TGA results showed that the NiCoFe2O4 nanoparticles have improved the thermal stability of PoPD. Dielectric properties of PoPD/NiCoFe2O4 nanocomposites at different temperatures have been carried in the frequency range 50 Hz to 5 MHz.

Nitrate removal by Fe0/Pd/Cu nano-composite in groundwater.

Science.gov (United States)

Liu, Hongyuan; Guo, Min; Zhang, Yan

2014-01-01

Nitrate pollution in groundwater shows a great threat to the safety of drinking water. Chemical reduction by zero-valent iron is being considered as a promising technique for nitrate removal from contaminated groundwater. In this paper, Fe0/Pd/Cu nano-composites were prepared by the liquid-phase reduction method, and batch experiments of nitrate reduction by the prepared Fe0/Pd/Cu nano-composites under various operating conditions were carried out. It has been found that nano-Fe0/Pd/Cu composites processed dual functions: catalytic reduction and chemical reduction. The introduction of Pd and Cu not only improved nitrate removal rate, but also reduced the generation of ammonia. Nitrate removal rate was affected by the amount of Fe0/Pd/Cu, initial nitrate concentration, solution pH, dissolved oxygen (DO), reaction temperature, the presence of anions, and organic pollutant. Moreover, nitrate reduction by Fe0/Pd/Cu composites followed the pseudo-first-order reaction kinetics. The removal rate of nitrate and total nitrogen were about 85% and 40.8%, respectively, under the reaction condition of Fe-6.0%Pd-3.0%Cu amount of 0.25 g/L, pH value of 7.1, DO of 0.42 mg/L, and initial nitrate concentration of 100 mg/L. Compared with the previous studies with Fe0 alone or Fe-Cu, nano-Fe-6%Pd-3%Cu composites showed a better selectivity to N2.

Nanocrystalline Pd:NiFe{sub 2}O{sub 4} thin films: A selective ethanol gas sensor

Energy Technology Data Exchange (ETDEWEB)

Rao, Pratibha; Godbole, R.V.; Bhagwat, Sunita, E-mail: smb.agc@gmail.com

2016-10-15

In this work, Pd:NiFe{sub 2}O{sub 4} thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe{sub 2}O{sub 4} thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost. - Highlights: • Ethanol gas sensors based on Pd:NiFe{sub 2}O{sub 4} nanoparticle thin film were fabricated. • Pd incorporation in NiFe{sub 2}O{sub 4} matrix inhibits grain growth. • The sensors were more selective to ethanol gas. • Sensors exhibited fast response and recovery when doped with palladium. • Pd:NiFe{sub 2}O{sub 4} thin film sensor displays excellent long–term stability.

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

Perspective: Highly stable vapor-deposited glasses

Science.gov (United States)

Ediger, M. D.

2017-12-01

This article describes recent progress in understanding highly stable glasses prepared by physical vapor deposition and provides perspective on further research directions for the field. For a given molecule, vapor-deposited glasses can have higher density and lower enthalpy than any glass that can be prepared by the more traditional route of cooling a liquid, and such glasses also exhibit greatly enhanced kinetic stability. Because vapor-deposited glasses can approach the bottom of the amorphous part of the potential energy landscape, they provide insights into the properties expected for the "ideal glass." Connections between vapor-deposited glasses, liquid-cooled glasses, and deeply supercooled liquids are explored. The generality of stable glass formation for organic molecules is discussed along with the prospects for stable glasses of other types of materials.

Investigation of magnetic mesostructure of (Pd{sub 0.984}Fe{sub 0.016}){sub 0.95}Mn{sub 0.05} alloy by polarized neutrons

Energy Technology Data Exchange (ETDEWEB)

Gordeev, G. [Petersburg Nuclear Physics Institute RAS, 188300 Gatchina, St. Petersburg (Russian Federation)]. E-mail: ggordev@pnpi.spb.ru; Zabenkin, V. [Petersburg Nuclear Physics Institute RAS, 188300 Gatchina, St. Petersburg (Russian Federation); Axelrod, L. [Petersburg Nuclear Physics Institute RAS, 188300 Gatchina, St. Petersburg (Russian Federation); Lazebnik, I. [Petersburg Nuclear Physics Institute RAS, 188300 Gatchina, St. Petersburg (Russian Federation); Wagner, V. [Physikalish-Technishe Bundesanstalt D-38116, Braunschweig (Germany); Eckerlebe, H. [Forschung Zentrum GKSS, Geesthacht (Germany)

2007-07-15

Neutron depolarization measurements and a simple model for depolarization were used to determine the geometrical sizes of magnetic inhomogeneities in the (Pd{sub 0.984}Fe{sub 0.016}){sub 0.95}Mn{sub 0.05} alloy. Polarized small angle scattering shows an asymmetric part, which should be attributed to a chiral ordering of the spins.

Synthesis and characterization of pillared bentonite with Al, AL/Fe and impregnated with Pd; Sintese e caracterizacao de bentonitas pilarizadas com Al, AL/Fe e impregnadas com Pd

Energy Technology Data Exchange (ETDEWEB)

Silva, Marcus Vinicius Costa; Pizarro, Alejandro Herrero; Molina, Carmen Belen, E-mail: marcus.ufpa@yahoo.com.br [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Instituto de Tecnologia. Faculdade de Engenharia Quimica; Seccion de Ingenieria Quimica, Facultad de Ciencias, Universidad Autonoma de Madri (Spain)

2017-10-01

In this work, a north american bentonite was pillared with Al and Al/Fe, creating the Al-PILC and Al-Fe-PILC, respectively. Then the Pd was impregnated in the materials, generating Pd-Al-PILC and Pd-Al-Fe-PILC, respectively. The samples were characterized by X-ray diffraction, differential thermal analysis and thermogravimetric and N{sub 2} adsorption at 77 K to determine the specific surface area by BET method (Brunauer - Emmett - Teller). There was an increase in the basal spacing of bentonite from 12.4Å in the original sample to 17.81Å in the Al-Fe-PILC, 17.20Å in Pd-Al-PILC and 17.05Å in the Pd-Al-Fe-PILC. The specific surface area increased from 19.05m{sup 2}/g in the original sample to 173.49m{sup 2}/g in Al-Fe-PILC, 101.31m{sup 2}/g to Pd-Al-PILC and 92m{sup 2}/g in Pd-Al-Fe-PILC. The pillaring process was successful and the synthesized materials have great potential for use as catalysts. (author)

Reductive dechlorination of tetrachlorobisphenol A by Pd/Fe bimetallic catalysts

International Nuclear Information System (INIS)

Huang, Qiang; Liu, Wen; Peng, Ping’an; Huang, Weilin

2013-01-01

Highlights: • TCBPA can be rapidly and completely dechlorinated by Pd/Fe bimetallic catalysts. • The observed rate constants are functions of dosages, initial concentration, Pd coverage and solution pH. • Pd dosage is the major factor in the observed rates of the reaction. • This is the first report investigating the dechlorination of TCBPA by Pd/Fe catalysts. -- Abstract: The Pd/Fe bimetallic catalysts of micron sizes were synthesized and the rates of tetrachlorobisphenol A (TCBPA) degradation were measured under various conditions using a batch reactor system. The results showed that TCBPA was rapidly dechlorinated to tri-, di- and mono-chlorobisphenol A and to bisphenol A (BPA). The observed rate constants (k obs ) were found to increase as functions of the Pd coverage on the Fe particles and the dosages of the catalysts within the reactors. The k obs value decreased as the initial TCBPA concentration increased, suggesting that the TCBPA dechlorination may follow a surface-site limiting Langmuir–Hinshelwood rate model. The weakly acidic solution, especially at or near pH 6.0, also favored the dechlorination of TCBPA. At pH 6.0, Pd coverage of 0.044 wt% and catalyst dosage of 5 g L −1 , TCBPA with an initial concentration of 20 μM was completely transformed within 60 min, and BPA was detected as the major product through the reaction time. Meanwhile, the k obs values measured at constant solution pH correlated linearly with the mass of particle-bound Pd introduced to the reactors, regardless of Pd/Fe catalyst dosage or Pd surface coverage. This study suggested that Pd/Fe catalysts could be potentially employed to rapidly degrade TCBPA in the contaminated environment

Electronic Structure of Fe-Pd Alloys Studied by Using Photoemission Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nahm, T-U. [Hanyang University, Seoul (Korea, Republic of)

2017-07-15

We investigated the electronic structure of Fe{sub x}Pd{sub 1−x} (x = 0.25, 0.5, and 0.75) alloys by measuring valence-band and core-level photoelectron spectra. The Fe 3d and Pd 4d partial spectral weights were determined by using the Cooper minimum phenomenon of the Pd 4d photoionization cross section. We found that the experimentally determined Fe partial spectral weight of Fe{sub 50}Pd{sub 50} alloy differ much from the band calculation results, and we could not observe a spectral structure due to the Pd 4d states mixed with the Fe 3d majority states at the binding energy of 0.9 eV. We suggest that a plausible explanation for these discrepancies should be the spin-dependent lifetime of the Fe 3d states.

Thermal plasma chemical vapor deposition

International Nuclear Information System (INIS)

Heberlein, J.; Pfender, E.

1993-01-01

Thermal plasmas, with temperatures up to and even exceeding 10 4 K, are capable of producing high density vapor phase precursors for the deposition of relatively thick films. Although this technology is still in its infancy, it will fill the void between the relatively slow deposition processes such as physical vapor deposition and the high rate thermal spray deposition processes. In this chapter, the present state-of-the-art of this field is reviewed with emphasis on the various types of reactors proposed for this emerging technology. Only applications which attracted particular attention, namely diamond and high T c superconducting film deposition, are discussed in greater detail. (orig.)

Effect of MnCuFe{sub 2}O{sub 4} content on magnetic and dielectric properties of poly (O-Phenylenediamine)/MnCuFe{sub 2}O{sub 4} nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Kannapiran, Nagarajan [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India); Muthusamy, Athianna, E-mail: muthusrkv@gmail.com [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India); Chitra, Palanisamy [PG and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu (India)

2016-03-01

Poly o-phenylenediamine (PoPD)/MnCuFe{sub 2}O{sub 4} nanocomposites with three different ratios of MnCuFe{sub 2}O{sub 4} (10%, 20%, 30% w/w) were synthesized by in-situ oxidative chemical polymerization method ammonium persulphate used as oxidant, while MnCuFe{sub 2}O{sub 4} nanoparticles was prepared by auto-combustion method. The structure, morphology and magnetic properties of synthesized PoPD/MnCuFe{sub 2}O{sub 4} nanocomposites were characterized by FT-IR, UV–visible absorption spectra, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Vibrating sample magnetometer (VSM). FTIR spectra and XRD were confirmed the formation of the PoPD/MnCuFe{sub 2}O{sub 4} nanocomposites. The morphology of PoPD/MnCuFe{sub 2}O{sub 4} nanocomposites is visualized through SEM and TEM. The spherical morphology of the PoPD was confirmed using SEM analysis. Dielectric properties of PoPD/MnCuFe{sub 2}O{sub 4} nanocomposites at different temperatures have been performed in the frequency range of 50 Hz–5 MHz. The optical absorption experiments of PoPD/MnCuFe{sub 2}O{sub 4} nanocomposites reveal that the direct transition with an energy band gap is around 2 eV. - Highlights: • Green synthesis of PoPD (the polymerization carried out only in aqueous medium) by in-situ chemical polymerization method. • For the first time, PoPD incorporated with MnCuFe{sub 2}O{sub 4} with lesser particle size. • The auto combustion reaction, support to achieve less particle size. • Ferrite content affects the magnetic properties of the nanocomposites.

Photoelectrochemical energy conversion obtained with ultrathin organo-metallic-chemical-vapor-deposition layer of FeS[sub 2] (pyrite) on TiO[sub 2

Energy Technology Data Exchange (ETDEWEB)

Ennaoui, A.; Fiechter, S.; Tributsch, H. (Abt. Solare Energetik, Hahn-Meitner-Inst., D-1000 Berlin 39 (Germany)); Giersig, M.; Vogel, R.; Weller, H. (Abt. Photochemie, Hahn-Meitner-Inst., D-1000 Berlin 39 (Germany))

1992-09-01

Ultrathin (10 to 20 nm thick), polycrystalline films of FeS[sub 2] (pyrite) were grown on TiO[sub 2] (anatase) by chemical vapor deposition. The FeS[sub 2] films were characterized using optical absorption and high-resolution electron microscopy. Photoelectrochemical solar cells, using TiO[sub 2] (anatase) coated with FeS[sub 2] ultrathin films, generated high open-circuit photo-voltages, of up to 600 mV, compared with a single crystal of pyrite electrode (200 mV). The photoelectrochemical behavior shows a strong dependence of photovoltage and photocurrent on the pH of the solution. This paper reports that it is explained by electron injection from the conduction band of FeS[sub 2] to the conduction band of TiO[sub 2]. Regeneration of holes is taking place by electron transfer from the redox system in the electrolyte.

Nano-structure formation of Fe-Pt perpendicular magnetic recording media co-deposited with MgO, Al2O3 and SiO2 additives

International Nuclear Information System (INIS)

Safran, G.; Suzuki, T.; Ouchi, K.; Barna, P.B.; Radnoczi, G.

2006-01-01

Perpendicular magnetic recording media samples were prepared by sputter deposition on sapphire with a layer sequence of MgO seed-layer/Cr under-layer/FeSi soft magnetic under-layer/MgO intermediate layer/FePt-oxide recording layer. The effects of MgO, Al 2 O 3 and SiO 2 additives on the morphology and orientation of the FePt layer were investigated by transmission electron microscopy. The samples exhibited (001) orientation of the L1 FePt phase with the mutual orientations of sapphire substrate//MgO(100)[001]//Cr(100)[11-bar0]//FeSi(100)[11-bar0]//MgO(100) [001]//FePt(001)[100]. The morphology of the FePt films varied due to the co-deposited oxides: The FePt layers were continuous and segmented by stacking faults aligned at 54 o to the surface. Films with SiO 2 addition, beside the oriented columnar FePt grains, exhibited a fraction of misoriented crystallites due to random repeated nucleation. Al 2 O 3 addition resulted in a layered structure, i.e. an initial continuous epitaxial FePt layer covered by a secondary layer of FePt-Al 2 O 3 composite. Both components (FePt and MgO) of the MgO-added samples were grown epitaxially on the MgO intermediate layer, so that a nano-composite of intercalated (001) FePt and (001) MgO was formed. The revealed microstructures and formation mechanisms may facilitate the improvement of the structural and magnetic properties of the FePt-oxide composite perpendicular magnetic recording media

Ground state magnetic properties of Fe nanoislands on Cu(111)

International Nuclear Information System (INIS)

Kishi, Tomoya; David, Melanie; Nakanishi, Hiroshi; Kasai, Hideaki; Dino, Wilson Agerico; Komori, Fumio

2005-01-01

We investigate magnetic properties of Fe nanoislands on Cu(111) in the relaxed structure within the density functional theory. We observe that the nanoislands exhibit the ferromagnetic properties with large magnetic moment. We find that the change in the magnetic moment of each Fe atom is induced by deposition on Cu(111) and structure relaxation of Fe nanoislands. Moreover, we examine the stability of ferromagnetic states of Fe nanoislands by performing the total energy calculations. (author)

Spin-resolved magnetic studies of focused ion beam etched nano-sized magnetic structures

International Nuclear Information System (INIS)

Li Jian; Rau, Carl

2005-01-01

Scanning ion microscopy with polarization analysis (SIMPA) is used to study the spin-resolved surface magnetic structure of nano-sized magnetic systems. SIMPA is utilized for in situ topographic and spin-resolved magnetic domain imaging as well as for focused ion beam (FIB) etching of desired structures in magnetic or non-magnetic systems. Ultra-thin Co films are deposited on surfaces of Si(1 0 0) substrates, and ultra-thin, tri-layered, bct Fe(1 0 0)/Mn/bct Fe(1 0 0) wedged magnetic structures are deposited on fcc Pd(1 0 0) substrates. SIMPA experiments clearly show that ion-induced electrons emitted from magnetic surfaces exhibit non-zero electron spin polarization (ESP), whereas electrons emitted from non-magnetic surfaces such as Si and Pd exhibit zero ESP, which can be used to calibrate sputtering rates in situ. We report on new, spin-resolved magnetic microstructures, such as magnetic 'C' states and magnetic vortices, found at surfaces of FIB patterned magnetic elements. It is found that FIB milling has a negligible effect on surface magnetic domain and domain wall structures. It is demonstrated that SIMPA can evolve into an important and efficient tool to study magnetic domain, domain wall and other structures as well as to perform magnetic depth profiling of magnetic nano-systems to be used in ultra-high density magnetic recording and in magnetic sensors

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.

Bimetallic magnetic PtPd-nanoparticles as efficient catalyst for PAH removal from liquid media

Science.gov (United States)

Zanato, A. F. S.; Silva, V. C.; Lima, D. A.; Jacinto, M. J.

2017-11-01

Monometallic Pd- and bimetallic PtPd-nanoparticles supported on a mesoporous magnetic magnetite@silica matrix resembling a core-shell structure (Fe3O4@mSiO2) have been fabricated. The material was characterized by transmission electron microscope (TEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectra (XPS), energy dispersive spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). The catalysts were applied in the removal of anthracene from liquid phase via catalytic hydrogenation. It was found that anthracene as a model compound could be completely converted into the partially hydrogenated species by the monometallic and bimetallic solids. However, during the recycling study the bimetallic material (Fe3O4@mSiO2PtPd-) showed an enhanced activity towards anthracene removal compared with the monometallic materials. A single portion of the PtPd-based catalyst can be used up to 11 times in the hydrogenation of anthracene under mild conditions (6 atm of H2, 75 °C, 20 min). Thanks to the presence of a dense magnetic core, the catalysts were capable of responding to an applied external magnetic field and once the reaction was completed, catalyst/product separation was straightforward.

Hybrid Pd/Fe{sub 3}O{sub 4} nanowires: Fabrication, characterization, optical properties and application as magnetically reusable catalyst for the synthesis of N-monosubstituted ureas under ligand-free conditions

Energy Technology Data Exchange (ETDEWEB)

Nasrollahzadeh, Mahmoud, E-mail: mahmoudnasr81@gmail.com [Department of Chemistry, Faculty of Science, University of Qom, Qom 37185-359 (Iran, Islamic Republic of); Azarian, Abbas [Department of Physics, University of Qom, Qom (Iran, Islamic Republic of); Ehsani, Ali [Department of Chemistry, Faculty of Science, University of Qom, Qom 37185-359 (Iran, Islamic Republic of); Sajadi, S.Mohammad [Department of Petroleum Geoscience, Faculty of Science, Soran University, PO Box 624, Soran, Kurdistan Regional Government (Iraq); Babaei, Ferydon [Department of Physics, University of Qom, Qom (Iran, Islamic Republic of)

2014-07-01

Highlights: • Preparation of Pd/Fe{sub 3}O{sub 4} nanowires as magnetically reusable catalysts. • The optical properties of the catalyst were studied using Gans theory. • N-arylation of benzylurea and in situ hydrogenolysis of 1-benzyl-3-arylureas. - Abstract: This paper reports the synthesis and use of Pd/Fe{sub 3}O{sub 4} nanowires, as magnetically separable catalysts for ligand-free amidation coupling reactions of aryl halides with benzylurea under microwave irradiation. Then, the in situ hydrogenolysis of the products was performed to afford the N-monosubstituted ureas from good to excellent yields. This method has the advantages of high yields, simple methodology and easy work up. The catalyst can be recovered by using a magnet and reused several times without significant loss of its catalytic activity. The catalyst was characterized using the powder XRD, SEM, EDS and UV–vis spectroscopy. Experimental absorbance spectra was compared with results from the Gans theory.

Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes

Directory of Open Access Journals (Sweden)

Luis M. Rivera Gavidia

2017-05-01

Full Text Available Direct methanol fuel cells (DMFCs are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM and X-ray techniques such as photoelectron spectroscopy (XPS, diffraction (XRD and energy dispersive spectroscopy (EDX. The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M and temperatures (60 °C and 90 °C. The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm−2 at 90 °C with 10 M methanol, higher than supported Pd and Pt commercial catalysts, demonstrating that Fe addition yields structural changes to Pd crystal lattice that reduce the crossover effects in DMFC operation.

Impurities in chromium deposits produced by electroplating and physical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Dini, J.W.

1994-05-01

Impurity contents in electrodeposited (hexavalent and trivalent) chromium deposits and physically vapor deposited (thermal evaporation, electron beam evaporation and rf-sputtering) were compared. Oxygen is the key impurity obtained in electrodeposited films but it can be minimized in hexavalent plating solutions by operating at high temperature, e. g., 85 C. Electrodeposits produced in trivalent chromium plating solutions and physically vapor deposited films have much higher oxygen contents than electrodeposits produced in hexavalent chromium solutions operated at temperatures around 85 C. Depending on the target material used for physically vapor deposited films, these films can also have high amounts of other impurities.

One-step green synthesis of bimetallic Fe/Pd nanoparticles used to degrade Orange II

Energy Technology Data Exchange (ETDEWEB)

Luo, Fang; Yang, Die; Chen, Zuliang, E-mail: zuliang.chen@newcastle.edu.au; Megharaj, Mallavarapu; Naidu, Ravendra

2016-02-13

Highlights: • Green synthesis of bimetallic Fe/Pd NPs was firstly reported using the one-step method. • 98.0% of Orange II was removed by Fe/Pd NPs, but only 16.0% by Fe NPs. • Fe/Pd NPs with a diameter ranging from 10 to 100 nm were observed. • Removing Orange II using Fe/Pd NPs involved both adsorption and catalytic degradation. - Abstract: To reduce cost and enhance reactivity, bimetallic Fe/Pd nanoparticles (NPs) were firstly synthesized using grape leaf aqueous extract to remove Orange II. Green synthesized bimetallic Fe/Pd NPs (98.0%) demonstrated a far higher ability to remove Orange II in 12 h compared to Fe NPs (16.0%). Meanwhile, all precursors, e.g., grape leaf extract, Fe{sup 2+} and Pd{sup 2+}, had no obvious effect on removing Orange II since less than 2.0% was removed. Kinetics study revealed that the removal rate fitted well to the pseudo-first-order reduction and pseudo-second-order adsorption model, meaning that removing Orange II via Fe/Pd NPs involved both adsorption and catalytic reduction. The remarkable stability of Fe/Pd NPs showed the potential application for removing azo dyes. Furthermore, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the changes in Fe/Pd NPs before and after reaction with Orange II. High Performance Liquid Chromatography–Mass Spectrum (HPLC–MS) identified the degraded products in the removal of Orange II, and finally a removal mechanism was proposed. This one-step strategy using grape leaf aqueous extract to synthesize Fe/Pd NPs is simple, cost-effective and environmentally benign, making possible the large-scale production of Fe/Pd NPs for field remediation.

On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

Directory of Open Access Journals (Sweden)

Handuja Sangeeta

2010-01-01

Full Text Available Abstract Carbon nanotubes (CNTs were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.

Morphology, magnetic and resonance properties of Fe/MgO multilayers

International Nuclear Information System (INIS)

Garcia-Garcia, A; Algarabel, P A; Ibarra, M R; Vovk, A; Strichovanec, P; Pardo, J A; Magen, C; Golub, V; Salyuk, O

2011-01-01

Magnetic, resonance and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers prepared by pulsed laser deposition were investigated. Comparison of the data allows conclusions on Fe layers morphology. For t 1.25 nm a continuous coverage of MgO by Fe takes place. However, the morphology of Fe layers is rough. This causes the appearance of magnetostatic resonance modes analogous to those observed for continuous films deposited on embossed surfaces.

NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

Energy Technology Data Exchange (ETDEWEB)

Mlynczak, E. [Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow (Poland); Luches, P. [S3, Istituto Nanoscienze-CNR, Via G. Campi 213/a, I-41125 Modena (Italy); Valeri, S. [S3, Istituto Nanoscienze-CNR, Via G. Campi 213/a, I-41125 Modena (Italy); Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Universita di Modena e Reggio Emilia, Via G. Campi 213/a, 41100 Modena (Italy); Korecki, J. [Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow (Poland); Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al.Mickiewicza 30, 30-059 Krakow (Poland)

2013-06-21

The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

KAUST Repository

Song, Hyon Min

2015-01-13

The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P42/mmc) with cell parameters of a = 3.050 Å and c = 5.344 Å, which are slightly larger than in the bulk phase (a = 3.03 Å, c = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs.

Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

Energy Technology Data Exchange (ETDEWEB)

Lakshmanan, Saravanan; Rao, Subha Krishna [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Muthuvel, Manivel Raja [Defence Metallurgical Research Laboratory (DMRL), Hyderabad 500058 (India); Chandrasekaran, Gopalakrishnan [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Therese, Helen Annal, E-mail: helen.a@ktr.srmuniv.ac.in [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India)

2017-08-01

Highlights: • Ta/CoFeB(50 nm)/Ta thin films were deposited at various substrate temperatures (T{sub s}). • CoFeB films deposited at T{sub s} such as RT, 450 °C, 475 °C and 500 °C exhibited perpendicular coercivity. • CoFeB deposited at 475 °C displayed a higher coercivity of 315 Oe and a low M{sub s} of 169 emu/cc. • The enhanced crystallization of CoFeB at the Ta/CoFeB interface results in higher H{sub c} (⟂). - Abstract: Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (T{sub s}) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (M{sub s}) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

International Nuclear Information System (INIS)

Zhou, Hongyi; Han, Jian; Baig, Shams Ali; Xu, Xinhua

2011-01-01

Highlights: ► CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. ► Particle stability, ζ-potential and IEP of non- and stabilized Pd/Fe were compared. ► Dechlorination of 2,4-D by different Pd/Fe systems was investigated. ► The reaction mechanism has been discussed and presented in the article. ► Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L −1 ) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11.5 to 2.5. The optimal CMC/Fe mass ratio for the dechlorination of 2,4-D was determined to be 5/1, and the removal of 2,4-D was

Chemical vapor deposition and electric characterization of perovskite oxides LaMO3 (M=Co, Fe, Cr and Mn) thin films

International Nuclear Information System (INIS)

Ngamou, Patrick Herve Tchoua; Bahlawane, Naoufal

2009-01-01

Oxides with a perovskite structure are important functional materials often used for the development of modern devices. In view of extending their applicability, it is necessary to efficiently control their growth as thin films using technologically relevant synthesis methods. Pulsed spray evaporation CVD was used to grow several perovskite-type oxides on planar silicon substrates at temperatures ranging from 500 to 700 deg. C. The optimization of the process control parameters allows the attainment of the perovskite structure as a single phase. The electrical characterization using the temperature-dependent conductivity and thermopower indicates the p-type conduction of the grown films and shows a decreasing concentration of the charge carrier, mobility and band gap energy in the sequence LaCoO 3 >LaMnO 3 >LaCrO 3 >LaFeO 3 . The investigation of the electric properties of the obtained perovskite thin films shows the versatility of CVD as a method for the development of innovative devices. - Graphical abstract: We report a single step deposition of perovskite thin films LaMO 3 (M: Co, Mn, Cr, Fe) using pulsed spray evaporation chemical vapor deposition. Electrical and thermopower properties, similar to these of bulk materials, could promote the development of modern thermoelectric devices based on thin films technology.

Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

Science.gov (United States)

Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

2016-10-01

In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

An experimental study of the magnetic ordering in Pd-based Fe and Mn alloys

International Nuclear Information System (INIS)

Verbeek, B.H.

1979-01-01

This thesis presents the results of an investigation on the magnetic ordering phenomena in some Pd based alloys with small concentrations of magnetic impurities. It has been the object to explore the ordering mechanisms in these alloys which lead to various types of magnetism at low temperature. The experimental techniques used are described. (Auth.)

Iron selenide films by aerosol assisted chemical vapor deposition from single source organometallic precursor in the presence of surfactants

Energy Technology Data Exchange (ETDEWEB)

Hussain, Raja Azadar [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Badshah, Amin, E-mail: aminbadshah@yahoo.com [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Younis, Adnan [School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW (Australia); Khan, Malik Dilshad [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Akhtar, Javeed [Department of Physics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan)

2014-09-30

This article presents the synthesis and characterization (multinuclear nuclear magnetic resonance, Fourier transform infrared spectroscopy, carbon–hydrogen–nitrogen–sulfur analyzer, atomic absorption spectrometry and thermogravimetric analysis) of a single source organometallic precursor namely 1-acetyl-3-(4-ferrocenylphenyl)selenourea for the fabrication of iron selenide (FeSe) films on glass substrates using aerosol assisted chemical vapor deposition (AACVD). The changes in the morphologies of the films have been monitored by the use of two different surfactants i.e. triton X-100 and tetraoctylphosphonium bromide during AACVD. The role of surfactant has been evaluated by examining the interaction of the surfactants with the precursor by using UV–vis spectroscopy and cyclic voltammetry. The fabricated FeSe films have been characterized with powder X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. - Highlights: • Ferrocene incorporated selenourea (FIS) has been synthesized and characterized. • FeSe thin films have been fabricated from FIS. • Mechanism of film growth was studied with cyclic voltammetry and UV–vis spectroscopy.

Synthesis and characterization of magnetic Fe/CNTs composites with controllable Fe nanoparticle concentration

International Nuclear Information System (INIS)

Zhao Fan; Duan Hongyan; Wang Weigao; Wang Jun

2012-01-01

Fe/CNTs composites, with different concentrations of Fe nanoparticles (NPs) on carbon nanotube (CNT) surfaces, were successfully fabricated via a facile solvothermal method. The lengths of CNTs are up to 10 μm and the mean diameter of the Fe nanoparticles is about 25 nm. The structures, composition and magnetic properties of the Fe/CNTs were characterized by XRD, FTIR, FE-SEM, TEM and PPMS. We found that the concentrations of Fe nanoparticles depositing on the CNTs could be controlled by adjusting the initial mass ratio of ferrocene to CNTs. The Fe/CNTs composites display good ferromagnetic properties at room temperature, with a saturation magnetization of 125 emu/g-Fe and a coercivity of 276 Oe. The Curie temperature of the sample is about 1038 K, slightly lower than that (1043 K) of the bulk iron.

A Temperature Window for the Synthesis of Single-Walled Carbon Nanotubes by Catalytic Chemical Vapor Deposition of CH4over Mo2-Fe10/MgO Catalyst

Directory of Open Access Journals (Sweden)

Yu Ouyang

2009-01-01

Full Text Available Abstract A temperature window for the synthesis of single-walled carbon nanotubes by catalytic chemical vapor deposition of CH4over Mo2-Fe10/MgO catalyst has been studied by Raman spectroscopy. The results showed that when the temperature is lower than 750 °C, there were few SWCNTs formed, and when the temperature is higher than 950 °C, mass amorphous carbons were formed in the SWCNTs bundles due to the self-decomposition of CH4. The temperature window of SWCNTs efficient growth is between 800 and 950 °C, and the optimum growth temperature is about 900 °C. These results were supported by transmission electron microscope images of samples formed under different temperatures. The temperature window is important for large-scale production of SWCNTs by catalytic chemical vapor deposition method.

Microstructure of vapor deposited coatings on curved substrates

Energy Technology Data Exchange (ETDEWEB)

Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G., E-mail: haydn@virginia.edu [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., P.O. Box 400745, Charlottesville, Virginia 22904 (United States)

2015-09-15

Thermal barrier coating systems consisting of a metallic bond coat and ceramic over layer are widely used to extend the life of gas turbine engine components. They are applied using either high-vacuum physical vapor deposition techniques in which vapor atoms rarely experience scattering collisions during propagation to a substrate, or by gas jet assisted (low-vacuum) vapor deposition techniques that utilize scattering from streamlines to enable non-line-of-sight deposition. Both approaches require substrate motion to coat a substrate of complex shape. Here, direct simulation Monte Carlo and kinetic Monte Carlo simulation methods are combined to simulate the deposition of a nickel coating over the concave and convex surfaces of a model airfoil, and the simulation results are compared with those from experimental depositions. The simulation method successfully predicted variations in coating thickness, columnar growth angle, and porosity during both stationary and substrate rotated deposition. It was then used to investigate a wide range of vapor deposition conditions spanning high-vacuum physical vapor deposition to low-vacuum gas jet assisted vapor deposition. The average coating thickness was found to increase initially with gas pressure reaching a maximum at a chamber pressure of 8–10 Pa, but the best coating thickness uniformity was achieved under high vacuum deposition conditions. However, high vacuum conditions increased the variation in the coatings pore volume fraction over the surface of the airfoil. The simulation approach was combined with an optimization algorithm and used to investigate novel deposition concepts to tailor the local coating thickness.

Microstructure of vapor deposited coatings on curved substrates

International Nuclear Information System (INIS)

Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G.

2015-01-01

Thermal barrier coating systems consisting of a metallic bond coat and ceramic over layer are widely used to extend the life of gas turbine engine components. They are applied using either high-vacuum physical vapor deposition techniques in which vapor atoms rarely experience scattering collisions during propagation to a substrate, or by gas jet assisted (low-vacuum) vapor deposition techniques that utilize scattering from streamlines to enable non-line-of-sight deposition. Both approaches require substrate motion to coat a substrate of complex shape. Here, direct simulation Monte Carlo and kinetic Monte Carlo simulation methods are combined to simulate the deposition of a nickel coating over the concave and convex surfaces of a model airfoil, and the simulation results are compared with those from experimental depositions. The simulation method successfully predicted variations in coating thickness, columnar growth angle, and porosity during both stationary and substrate rotated deposition. It was then used to investigate a wide range of vapor deposition conditions spanning high-vacuum physical vapor deposition to low-vacuum gas jet assisted vapor deposition. The average coating thickness was found to increase initially with gas pressure reaching a maximum at a chamber pressure of 8–10 Pa, but the best coating thickness uniformity was achieved under high vacuum deposition conditions. However, high vacuum conditions increased the variation in the coatings pore volume fraction over the surface of the airfoil. The simulation approach was combined with an optimization algorithm and used to investigate novel deposition concepts to tailor the local coating thickness

Study on purification of carbon nano tubes grown on Fe/Ni bimetallic catalyst supported on Mg O by thermal chemical vapor deposition

International Nuclear Information System (INIS)

Mirershadi, S.; Mortazavi, Z.; Reyhani, A.; Norouzian, Sh.; Moniri, N.; Novinrooz, A. J.

2007-01-01

Carbon nano tubes grown on Fe/Ni bimetallic catalysts supported on Mg O by thermal chemical vapor deposition. Then purification of carbon nano tubes by oxidation under air at atmospheric pressure and acid treatment with HCl, have been studied. The Scanning electron microscopy observation showed impurities with carbon nano tubes. Scanning electron microscopy, XRD, Raman spectroscopy and Thermogravimetric analysis/Differential Scanning Calorimetry techniques have been used to investigate the effect of purification of carbon nano tubes on morphology and structural quality of them. The weight ratio of carbon nano tubes in purified sample re saved to 85/8 %.

Fabrication and magnetic properties of Fe/GaAs/Fe hybrid structures

OpenAIRE

Wong, P.K.J.; Zhang, W.; Zhang, W.; Wu, J.; Will, I.G.; Xu, Y.B.; Farrer, I.; Ritchie, D.A.

2010-01-01

In this contribution, experimental results on the fabrication and magnetic characterization of a novel type vertical Fe/GaAs(100)/Fe spin-valve (SV) spintronic device are presented. An array of techniques has been developed by combining use of ex-situ chemical and selective etching of GaAs/AlGaAs/n-GaAs epilayers and ultrahigh vacuum deposition of Fe by molecular beam epitaxy (MBE). The thinnest achievable GaAs membrane by these sequences can be as thin as 50 nm.

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.

Carbon diffusion in uncoated and titanium nitride coated iron substrates during microwave plasma assisted chemical vapor deposition of diamond

International Nuclear Information System (INIS)

Weiser, P.S.; Prawer, S.; Manory, R.R.; Paterson, P.J.K.; Stuart, Sue-Anne

1992-01-01

Auger Electron Spectroscopy has been employed to investigate the effectiveness of thin films of TiN as barriers to carbon diffusion during Chemical Vapor Deposition (CVD) of diamond onto Fe substrates. Auger Depth Profiling was used to monitor the C concentration in the TiN layer, through the interface and into the substrate both before and after CVD diamond deposition. The results show that a layer of TiN only 250 Angstroems thick is sufficient to inhibit soot formation on the Fe surface and C diffusion into the Fe bulk. 14 refs., 4 figs

The hydrogen interaction in an FCC FePd alloy with a vacancy

Energy Technology Data Exchange (ETDEWEB)

Ardenghi, S [Instituto de AstronomIa y Fisica del Espacio (IAFE), CC 67-Suc 28 (C1428ZAA) Ciudad Autonoma de Buenos Aires (Argentina); Gonzalez, E; Jasen, P; Juan, A [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253 BahIa Blanca (8000) (Argentina)], E-mail: cajuan@uns.edu.ar

2009-04-15

The absorption of hydrogen in the ordered face-centered cubic FePd alloy is investigated using a density functional calculation method. Changes in the electronic structure and bonding after introducing an Fe or Pd vacancy are analysed. H locates close to a tetrahedral site and the H-metal bond is achieved at the expense of the interfacial Fe-Pd bond.

Investigation of Fe-Si-N films as magnetic overcoat for high density recording disk drives

International Nuclear Information System (INIS)

Gauvin, M.; Talke, F. E.; Fullerton, E. E.

2010-01-01

A 50-nm-thick Fe-Si-N films were deposited via reactive magnetron cosputtering of independent Fe and Si targets, in Ar/N 2 gas mixture, under different dc Fe target power conditions. Magnetic properties, mechanical hardness and tribological properties were characterized as a function of the Fe target power by magnetometry, nanoindentation, and nanoscratch testing, respectively. Deposited samples were found to be ferromagnetic with a coercivity of approximately 20 Oe and a saturation magnetization increasing from 200 to 1100 emu/cm 3 as a function of Fe sputter power, i.e., values typical of soft magnetic materials. The mechanical hardness was found to be between 50% and 70% of the hardness of a pure SiN x film. Nanotribological properties of films deposited with a Fe target power ≥80 W degraded rapidly.

Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhou, Hongyi, E-mail: zhouhy@zjut.edu.cn [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Han, Jian [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Baig, Shams Ali; Xu, Xinhua [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China)

2011-12-30

Highlights: Black-Right-Pointing-Pointer CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. Black-Right-Pointing-Pointer Particle stability, {zeta}-potential and IEP of non- and stabilized Pd/Fe were compared. Black-Right-Pointing-Pointer Dechlorination of 2,4-D by different Pd/Fe systems was investigated. Black-Right-Pointing-Pointer The reaction mechanism has been discussed and presented in the article. Black-Right-Pointing-Pointer Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L{sup -1}) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11

MgB2 thin films by hybrid physical-chemical vapor deposition

International Nuclear Information System (INIS)

Xi, X.X.; Pogrebnyakov, A.V.; Xu, S.Y.; Chen, K.; Cui, Y.; Maertz, E.C.; Zhuang, C.G.; Li, Qi; Lamborn, D.R.; Redwing, J.M.; Liu, Z.K.; Soukiassian, A.; Schlom, D.G.; Weng, X.J.; Dickey, E.C.; Chen, Y.B.; Tian, W.; Pan, X.Q.; Cybart, S.A.; Dynes, R.C.

2007-01-01

Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB 2 thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB 2 films. The epitaxial pure MgB 2 films grown by HPCVD show higher-than-bulk T c due to tensile strain in the films. The HPCVD films are the cleanest MgB 2 materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB 2 . The carbon-alloyed HPCVD films demonstrate record-high H c2 values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB 2 Josephson junctions

Kinetics of 2-chlorobiphenyl Reductive Dechlorination by Pd-fe0 Nanoparticles

Directory of Open Access Journals (Sweden)

Jiang Junrong

2016-01-01

Full Text Available Kinetics of 2-chlorobiphenyl (2-Cl BP catalytic reductive dechlorination by Pd-Fe0 nanoparticles were investigated. Experimental results showed that ultrafine bimetallic Pd-Fe0e nanoparticles were synthesized in the presence of 40 kHz ultrasound in order to enhance disparity and avoid agglomeration. The application of ultrasonic irradiation during the synthesis of Pd-Fe0 nanoparticles further accelerated the dechlorinated removal ratio of 2-Cl BP. Up to 95.0% of 2-Cl BP was removed after 300 min reaction with the following experimental conditions: initial 2-Cl BP concentration 10 mg L-1, Pd content 0.8 wt. %, bimetallic Pd-Fe0 nanoparticles prepared in the presence of ultrasound available dosage 7g L-1, initial pH value in aqueous solution 3.0, and reaction temperature 25°C. The catalytic reductive dechlorination of 2-Cl BP followed pseudo-first-order kinetics and the apparent pseudo-first-order kinetics constant was 0.0143 min-1.

Morphology, magnetic and resonance properties of Fe/MgO multilayers

Energy Technology Data Exchange (ETDEWEB)

Garcia-Garcia, A; Algarabel, P A; Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC 50009 Zaragoza (Spain); Vovk, A [Centro de Fisica da Materia Condensada Unversidade de Lisboa, Campo Grande Ed. C8, 1749-016, Lisboa (Portugal); Strichovanec, P; Pardo, J A; Magen, C [Instituto de Nanociencia de Aragon, Universidad de Zaragoza 50018 Zaragoza (Spain); Golub, V; Salyuk, O, E-mail: ayvovk@fc.ul.pt [Institute of Magnetism NAS of Ukraine, 36-b Vernnadsky blvd., 03142, Kyiv (Ukraine)

2011-07-06

Magnetic, resonance and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers prepared by pulsed laser deposition were investigated. Comparison of the data allows conclusions on Fe layers morphology. For t<0.61 nm typical features of granular cermet films in dielectric regime are observed, i.e. high electrical resistance, isotropic magnetoresistance and strong temperature dependence of magnetization. For higher t coalescence of Fe granules occurs and metallic percolation cluster is formed at t{approx}0.81 nm. This is manifested by rapid decrease of films resistance and formation of multipeak ferromagnetic resonance spectra. For t>1.25 nm a continuous coverage of MgO by Fe takes place. However, the morphology of Fe layers is rough. This causes the appearance of magnetostatic resonance modes analogous to those observed for continuous films deposited on embossed surfaces.

Structural and magnetic properties of epitaxial delafossite CuFeO{sub 2} thin films grown by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Joshi, Toyanath; Senty, Tess R.; Trappen, Robbyn; Zhou, Jinling; Borisov, Pavel; Holcomb, Mikel B.; Bristow, Alan D.; Lederman, David [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Chen, Song; Song, Xueyan [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6070 (United States); Ferrari, Piero; Cabrera, Alejandro L. [Pontificia Universidad Catolica, Instituto de Física, Santiago (Chile)

2015-01-07

Growth of pure phase delafossite CuFeO{sub 2} thin films on Al{sub 2}O{sub 3} (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO{sub 2} films demonstrated a phase transition at T{sub C} ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO{sub 2}. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.

Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

Science.gov (United States)

Lakshmanan, Saravanan; Rao, Subha Krishna; Muthuvel, Manivel Raja; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal

2017-08-01

Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (Ts) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (Ms) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

Facile fabrication of nanoporous PdFe alloy for nonenzymatic electrochemical sensing of hydrogen peroxide and glucose

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinping [Key Laboratory of Chemical Sensing and Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China); Wang, Zhihong [School of Basic Medical Sciences, Shandong University of Traditional Chinese Medicine, Jinan 250355 (China); Zhao, Dianyun [Key Laboratory of Chemical Sensing and Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China); Xu, Caixia, E-mail: chm_xucx@ujn.edu.cn [Key Laboratory of Chemical Sensing and Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China)

2014-06-01

Graphical abstract: Nanoporous PdFe alloy, characterized by open three-dimensional bicontinuous nanospongy architecture, was easily fabricated by selectively dealloying PdFeAl source alloys, which exhibits greatly enhanced sensing performance and structure stability towards H{sub 2}O{sub 2} and glucose compared with NP-Pd and Pd/C catalysts. - Highlights: • NP-PdFe alloy is fabricated by a simple dealloying method. • NP-PdFe possesses open three-dimensional bicontinuous spongy morphology. • NP-PdFe shows high electrochemical sensing activities towards H{sub 2}O{sub 2} and glucose. • NP-PdFe shows good long-term stability for H{sub 2}O{sub 2} and glucose detection. • NP-PdFe shows good reproducibility for H{sub 2}O{sub 2} and glucose detection. - Abstract: Nanoporous (NP) PdFe alloy is easily fabricated through one step mild dealloying of PdFeAl ternary source alloy in NaOH solution. Electron microscopy characterization demonstrates that selectively dissolving Al from PdFeAl alloy generates three-dimensional bicontinuous nanospongy architecture with the typical ligament size around 5 nm. Electrochemical measurements show that the NP-PdFe alloy exhibits the superior electrocatalytic activity and durability towards hydrogen peroxide (H{sub 2}O{sub 2}) detection compared with NP-Pd and commercial Pd/C catalysts. In addition, NP-PdFe performs high sensing performance towards H{sub 2}O{sub 2} in a wide linear range from 0.5 to 6 mM with a low detection limit of 2.1 μM. This nanoporous structure also can sensitively detect glucose over a wide concentration range (1–32 mM) with a low detection limit of 1.6 μM and high resistance against chloride ions. Along with these attractive features, the as-made NP-PdFe alloy also has a good anti-interference towards ascorbic acid, uric acid, and dopamine.

Improved battery performance using Pd nanoparticles synthesized on the surface of LiFePO4/C by ultrasound irradiation

Science.gov (United States)

Saliman, Muhammad Ali; Okawa, Hirokazu; Takai, Misaki; Ono, Yuki; Kato, Takahiro; Sugawara, Katsuyasu; Sato, Mineo

2016-07-01

LiFePO4 has been attracting interest as a cathode material for Li-ion batteries due to its high energy density, low cost, and eco-friendliness. The electrochemical performance of LiFePO4 is limited because it exhibits low Li-ion diffusivity and low electronic conductivity. Numerous solutions have been considered, such as carbon coating, which is widely known to improve the electronic conductivity of LiFePO4. The deposition of metal nanoparticles (NPs) on the surface of carbon-coated LiFePO4 further enhances the electronic conductivity. In this study, we deposited Pd NPs onto the surface of LiFePO4/C and investigated the resulting electrochemical performance. Sonochemical synthesis was used to prepare the metal NPs; the procedure did not require any surfactants and the reaction was rapid.

Perpendicular magnetic anisotropy in CoXPd100-X alloys for magnetic tunnel junctions

Science.gov (United States)

Clark, B. D.; Natarajarathinam, A.; Tadisina, Z. R.; Chen, P. J.; Shull, R. D.; Gupta, S.

2017-08-01

CoFeB/MgO-based perpendicular magnetic tunnel junctions (p-MTJ's) with high anisotropy and low damping are critical for spin-torque transfer random access memory (STT-RAM). Most schemes of making the pinned CoFeB fully perpendicular require ferrimagnets with high damping constants, a high temperature-grown L10 alloy, or an overly complex multilayered synthetic antiferromagnet (SyAF). We report a compositional study of perpendicular CoxPd alloy-pinned Co20Fe60B20/MgO based MTJ stacks, grown at moderate temperatures in a planetary deposition system. The perpendicular anisotropy of the CoxPd alloy films can be tuned based on the layer thickness and composition. The films were characterized by alternating gradient magnetometry (AGM), energy-dispersive X-rays (EDX), and X-ray diffraction (XRD). Current-in-plane tunneling (CIPT) measurements have also been performed on the compositionally varied CoxPd MTJ stacks. The CoxPd alloy becomes fully perpendicular at approximately x = 30% (atomic fraction) Co. Full-film MTJ stacks of Si/SiO2/MgO (13)/CoXPd100-x (50)/Ta (0.3)/CoFeB (1)/MgO (1.6)/CoFeB (1)/Ta (5)/Ru (10), with the numbers enclosed in parentheses being the layer thicknesses in nm, were sputtered onto thermally oxidized silicon substrates and in-situ lamp annealed at 400 °C for 5 min. CIPT measurements indicate that the highest TMR is observed for the CoPd composition with the highest perpendicular magnetic anisotropy.

Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability.

Science.gov (United States)

Sun, Wuzhu; Yang, Weiyi; Xu, Zhengchao; Li, Qi; Shang, Jian Ku

2016-01-27

Superparamagnetic nanocatalysts could minimize both the external and internal mass transport limitations and neutralize OH(-) produced in the reaction more effectively to enhance the catalytic nitrite reduction efficiency with the depressed product selectivity to undesirable ammonium, while possess an easy magnetic separation capability. However, commonly used qusi-monodispersed superparamagnetic Fe3O4 nanosphere is not suitable as catalyst support for nitrite reduction because it could reduce the catalytic reaction efficiency and the product selectivity to N2, and the iron leakage could bring secondary contamination to the treated water. In this study, protective shells of SiO2, polymethylacrylic acid, and carbon were introduced to synthesize Fe3O4@SiO2/Pd, Fe3O4@PMAA/Pd, and Fe3O4@C/Pd catalysts for catalytic nitrite reduction. It was found that SiO2 shell could provide the complete protection to Fe3O4 nanosphere core among these shells. Because of its good dispersion, dense structure, and complete protection to Fe3O4, the Fe3O4@SiO2/Pd catalyst demonstrated the highest catalytic nitrite reduction activity without the detection of NH4(+) produced. Due to this unique structure, the activity of Fe3O4@SiO2/Pd catalysts for nitrite reduction was found to be independent of the Pd nanoparticle size or shape, and their product selectivity was independent of the Pd nanoparticle size, shape, and content. Furthermore, their superparamagnetic nature and high saturation magnetization allowed their easy magnetic separation from treated water, and they also demonstrated a good stability during the subsequent recycling experiment.

Growth, microstructure, and hard magnetic properties of Nd-Fe-B layers; Wachstum, Mikrostruktur und hartmagnetische Eigenschaften von Nd-Fe-B-Schichten

Energy Technology Data Exchange (ETDEWEB)

Hannemann, U.

2004-07-01

In this thesis with pulsed laser deposition Nd-Fe-B layers were deposited. The Nd-Fe-B layers were deposited both on chromium and on tantalum buffers. The layers, which were deposed on tantalum buffers, showed a strong dependence of the nicrostructure and the magnetic properties on the deposition temperature. On layers which were deposited at deposition temperatures around 630 C on the tantalum buffer, the epitactical growth of Nd{sub 2}Fe{sub 14}B could be observed. Summarizingly these layers can be described as micrometer-large and parallely oriented single crystals.

Variation of magnetoimpedance of electrodeposited NiFe/Cu with deposition current density

Science.gov (United States)

Mishra, A. C.; Jha, A. K.

2017-12-01

An investigation about influence of deposition current density on electrodeposited magnetic film is reported in this paper. Ferromagnetic NiFe thin films were electrodeposited on copper wires of 100 μm diameter for various electrdepostion current densities ranging from 10 to 60 mA/cm2 maintaining equal thickness in all films. The composition of deposited film varied with deposition current density and in particular, a composition of Ni79Fe21 was achieved for a current density of 20 mA/cm2. The surface microstructure of the film deposited at the current density of 20 mA/cm2 was found to have excellent smoothness. The coercivity of the film was lowest and highest value of magnetoimpedance was measured for this film. The influence of current density on film composition and hence magnetic properties was attributed to the change of deposition mechanism.

Microstructural and magnetic characterizations of CoFeCu electrodeposited in self-assembled mesoporous silicon

Energy Technology Data Exchange (ETDEWEB)

Fortas, G., E-mail: g.fortas@gmail.com [Centre de Recherche en Technologie des Semi-conducteur pour l’Energétique, Bd. 2 Frantz Fanon, les sept merveilles B.P.140, Alger (Algeria); Université des Sciences et de la Technologie Houari Boumediene, Faculté des Physique, BP 32 El Alia 16111 Bab Ezzouar, Alger (Algeria); Haine, N. [Université des Sciences et de la Technologie Houari Boumediene, Faculté des Physique, BP 32 El Alia 16111 Bab Ezzouar, Alger (Algeria); Sam, S.; Gabouze, N. [Centre de Recherche en Technologie des Semi-conducteur pour l’Energétique, Bd. 2 Frantz Fanon, les sept merveilles B.P.140, Alger (Algeria); Saifi, A. [Université Mouloud Mammeri, laboratoire de physique et de chimie quantique, BP No. 17 RP Hasnaoua Tizi-Ouzou 15000 (Algeria); Ouir, S. [Université Said SDB, Route De Soumaa BP 270, Blida (Algeria); Menari, H. [Centre de Recherche en Technologie des Semi-conducteur pour l’Energétique, Bd. 2 Frantz Fanon, les sept merveilles B.P.140, Alger (Algeria)

2015-03-15

Self-assembled mesoporous silicon with quasi-regular pore arrangements has been fabricated by the electrochemical anodization process in hydrofluoric acid solution. CoFeCu was electrodeposited in this structure from a bath containing sodium acetate as a complexing agent with a pH value of 5. The effect of current density on the morphology, the structure and the magnetic properties of CoFeCu deposit was studied by SEM, EDS, DRX and VSM. It has been shown that the morphology and structure of samples were strongly influenced by the current density and etching duration. The micrographs show the vertical and branched nanowires and also a discontinuous growth of wires. Further, the growth of a thick layer from the grain boundaries of released CoFeCu wires is produced. The magnetic hysteresis loops demonstrate that the CoFeCu nanowires exhibit easy magnetic axis perpendicular to the PS channels axis when the current density varied from 3 to 10 mA/cm{sup 2}. Nevertheless, they reveal a no magnetic anisotropy of CoFeCu nanostructures deposited only in the outside of porous silicon, probably due to the vanishing the shape anisotropy. - Highlights: • CoFeCu deposit has been electrodeposited on self assembled mesoporous silicon. • SEM observation shows that CoFeCu embedded in Porous silicon channels. • Magnetic measurements show the anisotropy magnetic behavior of CoFeCu nanostructures. • The growth rate of nanowires is enhanced with an increase of current density.

Magnetic and structural characterizations on nanoparticles of FePt, FeRh and their composites

International Nuclear Information System (INIS)

Ko, Hnin Yu Yu; Suzuki, Takao; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Hirotsu, Yoshihiko

2008-01-01

The various compositions of FePt and FeRh nanoparticles, and their composite particles have been fabricated by the solution-phase chemical method and their magnetic properties characterized. High-resolution transmission electron microscopic observations indicate that mono-dispersed FeRh and FePt/FeRh nanoparticles are fabricated with the average size of 3-5 nm. However, larger size particles are distributed in the annealed state. From X-ray diffraction results, the as-deposited FeRh nanoparticles reveal a chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. Similarly, the annealed FePt nanoparticles show the L1 0 -phase fct structure although the fcc structure is apparent in the as-deposited state. It is also found that the first time in the exchange bias effect in the composite of ferromagnetic (FePt) and anti-ferromagnetic (FeRh) nanoparticles; result in a shift of the hysteresis loop after field cooling process

Laser vapor phase deposition of semiconductors

Energy Technology Data Exchange (ETDEWEB)

Karlov, N.V.; Luk' ianchuk, B.S.; Sisakian, E.V.; Shafeev, G.A.

1987-06-01

The pyrolytic effect of IR laser radiation is investigated with reference to the initiation and control of the vapor phase deposition of semiconductor films. By selecting the gas mixture composition and laser emission parameters, it is possible to control the deposition and crystal formation processes on the surface of semiconductors, with the main control action achieved due to the nonadiabatic kinetics of reactions in the gas phase and high temperatures in the laser heating zone. This control mechanism is demonstrated experimentally during the laser vapor deposition of germanium and silicon films from tetrachlorides on single-crystal Si and Ge substrates. 5 references.

Growth of graphene underlayers by chemical vapor deposition

International Nuclear Information System (INIS)

Fabiane, Mopeli; Khamlich, Saleh; Bello, Abdulhakeem; Dangbegnon, Julien; Momodu, Damilola; Manyala, Ncholu; Charlie Johnson, A. T.

2013-01-01

We present a simple and very convincing approach to visualizing that subsequent layers of graphene grow between the existing monolayer graphene and the copper catalyst in chemical vapor deposition (CVD). Graphene samples were grown by CVD and then transferred onto glass substrates by the bubbling method in two ways, either direct-transfer (DT) to yield poly (methyl methacrylate) (PMMA)/graphene/glass or (2) inverted transfer (IT) to yield graphene/PMMA/glass. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to reveal surface features for both the DT and IT samples. The results from FE-SEM and AFM topographic analyses of the surfaces revealed the underlayer growth of subsequent layers. The subsequent layers in the IT samples are visualized as 3D structures, where the smaller graphene layers lie above the larger layers stacked in a concentric manner. The results support the formation of the so-called “inverted wedding cake” stacking in multilayer graphene growth

Influence of the deposition-induced stress on the magnetic properties of magnetostrictive amorphous (Fe80Co20)80B20 multilayers with orthogonal anisotropy

International Nuclear Information System (INIS)

Gonzalez-Guerrero, Miguel; Prieto, Jose Luis; Sanchez, Pedro; Aroca, Claudio

2007-01-01

In this work, we experimentally justify that the control of the mechanical stress induced during the deposition of sputtered amorphous magnetostrictive (Fe 80 Co 20 ) 80 B 20 allows a custom design of its magnetic properties. FeCoB multilayers have been sputtered on thermal oxide Si substrates with different buffer materials. The crystalline quality and the thermomechanical properties of the buffer layer influence both the coercive and the anisotropy field. Those buffer layers with both high rigidity and poor thermal conductivity do not allow the dissipation of energy of the incoming sputtered material. Therefore, the mechanical stresses related to the deposition process cannot be released, leading to magnetic layers with high easy-axis coercive field and low anisotropy field. This shows that the mechanical stresses accumulated during deposition are a key parameter for the control of coercivity

Effect of Ti seed and spacer layers on structure and magnetic properties of FeNi thin films and FeNi-based multilayers

Energy Technology Data Exchange (ETDEWEB)

Svalov, A.V., E-mail: andrey.svalov@ehu.es [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Larrañaga, A. [SGIker, Servicios Generales de Investigación, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Kurlyandskaya, G.V. [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation)

2014-10-15

Highlights: • Fe{sub 19}Ni{sub 81} films and FeNi-based multilayers were prepared by magnetron sputtering. • The samples were deposited onto glass substrates at room temperature. • Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. • The thick Cu seed increases the coercive force of the magnetic layer. • The thin Ti spacer restores the magnetic softness of the Cu/Ti/FeNi multilayers. - Abstract: The microstructure and magnetic properties of sputtered permalloy films and FeNi-based multilayers prepared by magnetron sputtering have been studied. X-ray diffraction measurements indicate that Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. Ti/FeNi bilayers with high crystallographic quality have relatively low resistivity. The Ti seed layer does not influence the magnetic properties of FeNi film in Ti/FeNi bilayers, but the thick Cu seed layer leads to an increase of the coercive force of the magnetic layer. For the FeNi films deposited on thick Cu seed layer, the (0 1 0) and (0 0 2) diffraction peaks of hcp nickel were clearly observed. The thin Ti spacer between Cu and FeNi layers prevents the formation of the nickel phase and restores the magnetic softness of the FeNi layer in the Cu/Ti/FeNi sample. Obtained results can be important for the development of multilayer sensitive elements for giant magnetoimpedance or magnetoresistance detectors.

Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

Directory of Open Access Journals (Sweden)

Chun Dong

2011-01-01

Full Text Available Abstract A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe and high magnetization (900–1,000 emu/cm3 characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

Application and analysis of palladium vapor deposited on stainless steel for high temperature electrical contacts

International Nuclear Information System (INIS)

Jodeh, S.

2008-01-01

Using electron beam evaporation. Pd thin films of 300 nm thickness have been deposited on 301 stainless steel for high temperature electrical contact studies. The structure and compost ion of the helms were studied in detail x-ray diffraction (XRD), scanning electron microscopy (Sem), electron probe microanalysis (EPMA), and x-ray photoelectron spectroscopy (XP S) with sputter depth profiling. The contact properties such as contact resistance, fretting wear resistance, and thermal stability have been measured.The contact resistance rem ins low after heat-aging in air for 168 h at 150 and 200 deg., but increases significantly after heat-aging at 340 deg.. This increase in contact resistance is caused by the formation of about a 27 nm (1 μin.) thick Pdo. In contrast, the thickness of the Pdo is too thin to cause measurable contact resistance increases after heat-aging at 150 and 200 deg.. The fretting wear resistance of Pd coated 301 stainless steel is better than that of electroplated Sn of ser veal thousand nm thickness. Thus, vapor deposited Pd coating on 301 stainless steel may replace electroplated Sn for electrical contact application at elevated temperatures.

Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines.

Science.gov (United States)

Kucheriv, Olesia I; Shylin, Sergii I; Ksenofontov, Vadim; Dechert, Sebastian; Haukka, Matti; Fritsky, Igor O; Gural'skiy, Il'ya A

2016-05-16

Discovery of spin-crossover (SCO) behavior in the family of Fe(II)-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe(2+), square planar tetracyanometalates M(II)(CN)4(2-) (M(II) = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fe(II) ion has a pseudo-octahedral coordination environment supported by four μ4-tetracyanometallates forming its equatorial coordination environment. Depending on the nature of X and M, axial positions are occupied by two 2X-pyrazines (X = Cl and M(II) = Ni (1), Pd (2), Pt (3); X = Me and M(II) = Ni (4), Pd (5)) or one 2X-pyrazine and one water molecule (X = I and M(II) = Ni (7), Pd (8), Pt (9)), or, alternatively, two distinct Fe(II) positions with either two pyrazines or two water molecules (X = Me and M(II) = Pt (6)) are observed. Temperature behavior of magnetic susceptibility indicates that all compounds bearing FeN6 units (1-6) display cooperative spin transition, while Fe(II) ions in N5O or N4O2 surrounding are high spin (HS). Structural changes in the nearest Fe(II) environment upon low-spin (LS) to HS transition, which include ca. 10% Fe-N distance increase, lead to the cell expansion. Mössbauer spectroscopy is used to characterize the spin state of all HS, LS, and intermediate phases of 1-9 (see abstract figure). Effects of a pyrazine substituent and M(II) nature on the hyperfine parameters in both spin states are established.

Fe-Ag nanocomposites tailored by multilayer deposition

International Nuclear Information System (INIS)

Balogh, J.; Kaptas, D.; Kiss, L. F.; Csontos, M.; Mihaly, G.; Temst, K.; Van Haesendonck, C.

2005-01-01

Full text: Besides the usual co-deposition methods, thin films of Fe-Ag granular composites can be prepared by alternate deposition of the constituents [1] in the form of granular multilayers when the magnetic layer is discontinuous. The discontinuous Fe layers show superparamagnetic properties that can be tailored [2] by the thickness of both the magnetic and the spacer layers and their magnetization tends to align perpendicular to the sample plain at low temperatures. With following the blocking transition of the superparamagnetic particles by Moessbauer spectroscopy, it was recently shown [2] that continuous magnetic layers can be inserted into the granular multilayer structure without modifying the average magnetic grain size and the almost perpendicular magnetic alignment of the granular layers. The possibility of a simultaneous control over the superparamagnetic grain size, the amount and the stacking sequence of the continuous ferromagnetic layers makes these heterostructures suitable model materials for investigating the role of interactions among the magnetically different elements in nanocomposites. Moessbauer spectroscopy is an effective tool for studying the magnetic properties of the granular and the continuous layers selectively. Comparing the temperature and applied magnetic field dependence of the measured hyperfine fields to the bulk magnetization we found [2] that varying the stacking sequence of the different layers affected the low field magnetic susceptibility of the ferromagnetic layers more significantly than that of the superparamagnetic ones. The magnetoresistance was also shown to depend sensitively [3] on the layer sequence. Interleaved ferromagnetic layers change the shape of the magnetoresistance curves exhibiting a linear variation in small magnetic fields and effect the temperature dependence of the magnetoresistance measured in high magnetic fields. [1] J. Balogh, D. Kaptas, T. Kemeny, L. F. Kiss, T. Pusztai, and I. Vincze, Hyperfine

Effect of Pt coverage in Pt-deposited Pd nanostructure electrodes on electrochemical properties

Energy Technology Data Exchange (ETDEWEB)

Park, Ah-Reum; Lee, Young-Woo; Kwak, Da-Hee; Park, Kyung-Won [Soongsil University, Seoul (Korea, Republic of)

2015-06-15

We have fabricated Pt-deposited Pd electrodes via a two-gun sputtering deposition system by separately operating Pd and Pt target as a function of sputtering time of Pt target. For Pt-deposited Pd electrodes (Pd/Pt-X), Pd were first deposited on the substrates at 20 W for 5min, followed by depositing Pt on the Pd-only electrodes as a function of sputtering time (X=1, 3, 5, 7, and 10min) at 20W on the Pt target. As the sputtering time of Pt target increased, the portion of Pt on the Pd electrodes increased, representing an increased coverage of Pt on the Pd electrodes. The Pd/Pt-7 electrode having an optimized Pt coverage exhibits an excellent electrocatalytic activity for methanol oxidation reaction.

Magnetically actuated bi-directional microactuators with permalloy and Fe/Pt hard magnet

International Nuclear Information System (INIS)

Pan, C.T.; Shen, S.C.

2005-01-01

Bi-directional polyimide (PI) electromagnetic microactuator with different geometries are designed, fabricated and tested. Fabrication of the electromagnetic microactuator consists of 10 μm thick Ni/Fe (80/20) permalloy deposition on the PI diaphragm by electroplating, high aspect ratio electroplating of copper planar coil with 10 μm in thickness, bulk micromachining, and excimer laser selective ablation. They were fabricated by a novel concept avoiding the etching selectivity and residual stress problems during wafer etching. A mathematical model is created by ANSYS software to analyze the microactuator. The external magnetic field intensity (H ext ) generated by the planar coil is simulated by ANSYS software. ANSYS software is used to predict the deflection angle of the microactuator. Besides, to provide bi-directional and large deflection angle of microactuator, hard magnet Fe/Pt is deposited at a low temperature of 300 deg. C by sputtering onto the PI diaphragm to produce a perpendicular magnetic anisotropic field. This magnetic field can enhance the interaction with H ext to induce attractive and repulsive bi-directional force to provide large displacement. The results of magnetic microactuator with and without hard magnets are compared and discussed. The preliminary result reveals that the electromagnetic microactuator with hard magnet shows a greater deflection angle than that without one

Reductive dechlorination of {gamma}-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nagpal, Varima; Bokare, Alok D. [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India); Chikate, Rajeev C. [Department of Chemistry, MES Abasaheb Garware College, Karve Road, Pune 411004 (India); Rode, Chandrashekhar V. [Chemical Engineering and Process Development Division, National Chemical Laboratory, Pune 411008 (India); Paknikar, Kishore M., E-mail: paknikar@vsnl.com [Center for Nanobioscience, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra (India)

2010-03-15

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane ({gamma}-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5 mg/L of lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m{sup 2}/g), manyfold greater that of commercial grade micro- or milli-scale iron particles ({approx}1.6 m{sup 2}/g); and, (2) increased catalytic reactivity due to the presence of Pd on the surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity.

N2O decomposition over Fe/ZSM-5: reversible generation of highly active cationic Fe species

NARCIS (Netherlands)

Zhu, Q.; Hensen, E.J.M.; Mojet, B.L.; Wolput, van J.H.M.C.; Santen, van R.A.

2002-01-01

Fe-oxide species in Fe/ZSM-5 (prepared by chemical vapor deposition of FeCl3)-active in N2O decomposition-react with zeolite protons during high temperature calcination to give highly active cationic Fe species, this transformation being reversible upon exposure to water vapor at lower temperature

Magnetic and magneto-optical properties of FeRh thin films

International Nuclear Information System (INIS)

Inoue, Sho; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Yu Ko, Hnin Yu; Suzuki, Takao

2008-01-01

The magnetic and magneto-optical properties of FeRh thin films epitaxially deposited onto MgO(1 0 0) substrates by RF sputter-deposition system have been investigated in conjunction with the structure. An intriguing virgin effect has been found in the M-T curves of the as-deposited FeRh thin films, which is presumably interpreted in term of a change in structural phase when heating. Also, a (negative) maximum peak of Kerr rotation at around 3.8 eV has been observed when FeRh thin films are in ferromagnetic state. The polar Kerr rotation angle is found to increase at temperatures above 100 deg. C, which corresponds to the antiferromagnet (AF)-ferromagnet (FM) transition of FeRh thin films

Organo-Functionalization of Silicon Nanocrystals Synthesized by Inductively Coupled Plasma Chemical Vapor Deposition

Energy Technology Data Exchange (ETDEWEB)

Lee, Don-Sung; Choe, Dong-Hoe; Jeong, Hyun-Dam [Chonnam National University, Gwangju (Korea, Republic of); Yoo, Seung-Wan; Kim, Jung-Hyung [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

2016-05-15

Octadecyl-terminated silicon nanocrystals (ODE-Si NCs) are obtained via a surface-initiated thermal hydrosilylation reaction on hydride-terminated Si NCs (H-Si NCs). Pristine Si NCs were synthesized at the gram scale by using inductively coupled plasma chemical vapor deposition (ICP-CVD) . The H-Si NCs were produced through a chemical etching process with hydrofluoric acid (HF), ethanol (EtOH), and distilled water (d-H{sub 2}O). The results obtained from X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) indicate that the synthesized Si NCs obtained via ICP-CVD have diamond cubic-structured silicon with a grain size of 10 nm and a densely packed Si NC array consisting of individual NCs. Organo-functionalized Si NCs, i.e., ODE-Si NCs, are well soluble in organic solvent whereas pristine Si NCs synthesized through ICP-CVD are not. The surface chemistry of the ODE-Si NCs was confirmed via Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy ({sup 1}H-NMR), and field emission transmission electron microscopy (FE-TEM). Thereby, these newly synthesized and scalable organo-functionalized Si NCs are applicable as raw materials for practical use in devices by tuning the surface chemistry with various capping molecules.

Ultrasharp Si nanowires produced by plasma-enhanced chemical vapor deposition

Czech Academy of Sciences Publication Activity Database

Červenka, Jiří; Ledinský, Martin; Stuchlíková, The-Ha; Stuchlík, Jiří; Výborný, Zdeněk; Holovský, Jakub; Hruška, Karel; Fejfar, Antonín; Kočka, Jan

2010-01-01

Roč. 4, 1-2 (2010), s. 37-39 ISSN 1862-6254 R&D Projects: GA MŠk(CZ) LC06040; GA AV ČR KAN400100701; GA MŠk LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : nanowires * silicon * scanning electron microscopy * hemical vapor deposition * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.660, year: 2010 http://www3.interscience.wiley.com/ cgi -bin/fulltext/123213957/HTMLSTART

The annealing temperature dependences of microstructures and magnetic properties in electro-chemical deposited CoNiFe thin films

International Nuclear Information System (INIS)

Suharyadi, Edi; Riyanto, Agus; Abraha, Kamsul

2016-01-01

CoNiFe thin films with various compositions had been successfully fabricated using electro-chemical deposition method. The crystal structure of Co_6_5Ni_1_5Fe_2_0, Co_6_2Ni_1_5Fe_2_3, and Co_5_5Ni_1_5Fe_3_0 thin films was fcc, bcc-fcc mix, and bcc, respectively. The difference crystal structure results the difference in magnetic properties. The saturation magnetic flux density (Bs) of Co_6_5Ni_1_5Fe_2_0, Co_6_2Ni_1_5Fe_2_3, and Co_5_5Ni_1_5Fe_3_0 thin films was 1.89 T, 1.93 T, and 2.05 T, respectively. An optimal annealing temperature was determined for controlling the microstructure and magnetic properties of CoNiFe thin films. Depending on annealing temperature, the ratio of bcc and fcc structure varied without changing the film composition. By annealing at temperature of T ≥ 350°C, the intensity ratio of X-ray diffraction peaks for bcc(110) to fcc(111) increased. The increase of phase ratio of bcc(110) to fcc(111) caused the increase of Bs, from 1.89 T to 1.95 T. Coercivity (Hc) also increased after annealing, from 2.6 Oe to 18.6 Oe for fcc phase thin films, from 2.0 Oe to 12.0 Oe for fcc-bcc mix phase thin films, and 7.8 Oe to 8 Oe for bcc phase thin films. The changing crystal structures during annealing process indicated that the thermal treatment at high temperature cause the changing crystallinity and atomic displacement. The TEM bright-field images with corresponding selected-area electron diffraction (SAED) patterns showed that there are strongly effects of thermal annealing on the size of fcc and bcc phase crystalline grain as described by size of individual spot and discontinuous rings. The size of crystalline grains increased by thermal annealing. The evolution of bcc and fcc structures of CoNiFe during annealing is though to be responsible for the change of magnetic properties.

Session 6: Catalytic hydro-dehalogenation of halon 1211 (CBrClF{sub 2}) over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts

Energy Technology Data Exchange (ETDEWEB)

Hai, Yu; Kennedy, E.M.; Md Azhar, Uddin; Dlugogorski, B.Z. [Newcastle Univ., Process Safety and Environment Protection Group, School of Engineering, Callaghan, NSW (Australia)

2004-07-01

In the current study, we present the result of our investigation on the hydro-dehalogenation of halon 1211 with hydrogen over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts. In addition to dissociatively adsorbing hydrogen, Fe, Co and Ni themselves can facilitate cleavage of C-halogen bonds. The effect of the interaction of a second metal (Fe, Co and Ni) with Pd on the conversion of halon 1211 and selectivity to CH{sub 2}F{sub 2} for the catalytic hydro-dehalogenation of halon 1211 is discussed. Activated carbon is chosen as support in order to minimize the interaction of support with the metals. The obtained experimental results show that the introduction of Fe, Co and Ni to Pd catalysts has a significant influence on the catalytic hydro-dehalogenation of halon 1211, especially with respect to the selectivity to CH{sub 2}F{sub 2}. The presence of Fe increases the amount of halon 1211 adsorbed on the surface of catalysts and enhances the cleavage of C-halogen bonds in halon 1211, resulting in a higher halon 1211 conversion level and selectivity to hydrocarbons. Higher selectivity to CHBrF{sub 2} is ascribed to the secondary reaction: CF{sub 2} + HBr {yields} CHBrF{sub 2}. (authors)

Surface modification and its role in the preparation of FeSi gradient alloys with good magnetic property and ductility

Science.gov (United States)

Yu, Haiyuan; Bi, Xiaofang

2018-04-01

Realization of the effective Si penetration at a lower processing temperature is a challenge, but of significance in reducing the strict requirements for the equipment and realizing cost-cutting in production. In this work, we have modified the surface microstructure of Fe-3 wt%Si alloy by using surface mechanical attrition treatment. The modified surface microstructure is characteristic of nanocrystalline, which is found to significantly enhance the efficiency of subsequent Si penetration into the alloy, and successively leading to the decrease of penetration temperature up to 200 °C. As a consequence, the Si gradient distribution across thickness can be readily controlled by changing penetration time, and FeSi alloys with various gradients are prepared by chemical vapor deposition along with subsequent annealing process. The dependence of magnetic and mechanical properties on Si gradient for demonstrates that the increase of Si gradient reduces core losses, especially at higher frequencies, and meanwhile improves ductility of FeSi alloys as well. The mechanism underlying the effect of Si gradient is clarified by combining magnetostriction measurement and domain structure observations. This work provides a facile and effective way for achieving gradient FeSi alloys with good magnetic property and ductility.

Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Chemical controls on alteration and mineralization

Science.gov (United States)

Henley, R.W.; Berger, B.R.

2011-01-01

Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays

Magnetic structure of molecular magnet Fe[Fe(CN) 6

Indian Academy of Sciences (India)

We have studied the magnetic structure of Fe[Fe(CN)6]·4H2O, prepared by precipitation method, using neutron diffraction technique. Temperature dependent DC magnetization study down to 4.2 K shows that the compound undergoes from a high temperature disordered (paramagnetic) to an ordered magnetic phase ...

High performance emitter for thermionic diode obtained by chemical vapor deposition

International Nuclear Information System (INIS)

Faron, R.; Bargues, M.; Durand, J.P.; Gillardeau, J.

1973-01-01

Vapor deposition process conditions presently known for tungsten and molybdenum (specifically the range of high temperatures and low pressures) permit the achievement of high performance thermionic emitters when used with an appropriate technology. One example of this uses the following series of successive vapor deposits, the five last vapor deposits constituting the fabrication of the emitting layer: Mo deposit for the formation of the nuclear fuel mechanical support; Mo deposit, which constitutes the sheath of the nuclear fuel; epitaxed Mo--W alloy deposit; epitaxed tungsten deposit; fine-grained tungsten deposit; and tungsten deposit with surface orientation according to plane (110)W. In accordance with vapor deposition techniques previously developed, such a sequence of deposits can easily be achieved with the same equipment, even without having to take out the part during the course of the process. (U.S.)

Fe3O4 thin films sputter deposited from iron oxide targets

International Nuclear Information System (INIS)

Peng, Yingguo; Park, Chandro; Laughlin, David E.

2003-01-01

Fe 3 O 4 thin films have been directly sputter deposited from a target consisting of a mixture of Fe 3 O 4 and Fe 2 O 3 onto Si and glass substrates. The magnetic properties and microstructures of the films have been characterized and correlated. The columnar growth of the Fe 3 O 4 grains was found to be initialized from the substrate surface without any critical thickness. Substrate bias was found to be a very effective means of improving the crystal quality and magnetic properties of the thin films. The crystallographic defects revealed by high resolution transmission electron microscopy seem to be a characteristic of the films prepared by this method

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.

Adsorption of guaiacol on Fe (110) and Pd (111) from first principles

Science.gov (United States)

Hensley, Alyssa J. R.; Wang, Yong; McEwen, Jean-Sabin

2016-06-01

The catalytic properties of surfaces are highly dependent upon the effect said surfaces have on the geometric and electronic structure of adsorbed reactants, products, and intermediates. It is therefore crucial to have a surface-level understanding of the adsorption of the key species in a reaction in order to design active and selective catalysts. Here, we study the adsorption of guaiacol on Fe (110) and Pd (111) using dispersion-corrected density functional theory calculations as both of these metals are of interest as hydrodeoxygenation catalysts for the conversion of bio-oils to useable biofuels. Both vertical (via the oxygen functional groups) and horizontal (via the aromatic ring) adsorption configurations were examined and the resulting adsorption and molecular distortion energies showed that the vertical sites were only physisorbed while the horizontal sites were chemisorbed on both metal surfaces. A comparison of guaiacol's horizontal adsorption on Fe (110) and Pd (111) showed that guaiacol had a stronger adsorption on Pd (111) while the Fe (110) surface distorted the Csbnd O bonds to a greater degree. Electronic analyses on the horizontal systems showed that the greater adsorption strength for guaiacol on Pd (111) was likely due to the greater charge transfer between the aromatic ring and the surface Pd atoms. Additionally, the greater distortion of the Csbnd O bonds in adsorbed guaiacol on Fe (110) is likely due to the greater degree of interaction between the oxygen and surface Fe atoms. Overall, our results show that the Fe (110) surface has a greater degree of interaction with the functional groups and the Pd (111) surface has a greater degree of interaction with the aromatic ring.

Oxygen Barrier Coating Deposited by Novel Plasma-enhanced Chemical Vapor Deposition

DEFF Research Database (Denmark)

Jiang, Juan; Benter, M.; Taboryski, Rafael Jozef

2010-01-01

We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source. This confi......We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source...... effect of single-layer coatings deposited under different reaction conditions was studied. The coating thickness and the carbon content in the coatings were found to be the critical parameters for the barrier property. The novel barrier coating was applied on different polymeric materials...

Structure and magnetic properties of Co2FeSi film deposited on Si/SiO2 substrate with Cr buffer layer

Science.gov (United States)

Chatterjee, Payel; Basumatary, Himalay; Raja, M. Manivel

2018-05-01

Co2FeSi thin films of 25 nm thickness with 50 nm thick Cr buffer layer was deposited on thermally oxidized Si substrates. Structural and magnetic properties of the films were studied as a function of annealing temperature and substrate temperatures. While the coercivity increases with increase in annealing temperature, it is found to decrease with increase in substrate temperature. A minimum coercivity of 18 Oe has been obtained for the film deposited at 550°C substrate temperature. This was attributed to the formation of L12 phase as observed from the GIXRD studies. The films with a good combination of soft magnetic properties and L21 crystal structure are suitable for spintronic applications.

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.

Magnetic properties and microstructure of low ordering temperature L10 FePt thin films

International Nuclear Information System (INIS)

Sun, A.C.; Kuo, P.C.; Chen, S.C.; Chou, C.Y.; Huang, H.L.; Hsu, J.H.

2004-01-01

Polycrystalline Fe 52 Pt 48 alloy thin films were prepared by dc magnetron sputtering on preheated natural-oxidized silicon wafer substrates. The film thickness was varied from 10 to 100 nm. The as-deposited film was encapsulated in a quartz tube and postannealed in vacuum at various temperatures for 1 h, then furnace cooled. It is found that the ordering temperature from as-deposited soft magnetic fcc FePt phase to hard magnetic fct L1 0 FePt phase could be reduced to about 350 deg. C by preheating substrate and furnace cooling treatment. The magnetic properties measurements indicated that the in-plane coercivity of the films was increased rapidly as annealing temperature is increased from 300 to 400 deg. C, but it decreased when the annealing temperature is higher than 400 deg. C. X-ray diffraction analysis shown that the as-deposited FePt thin film was a disorder fcc FePt phase. The magnetic measurement indicated that the transformation of disorder fcc FePt to fct L1 0 FePt phase was started at about 350 deg. C, which is consistent with the analysis of x-ray diffraction patterns. From scanning electron microscopy observation and selected area energy disperse spectrum analysis, the distributions of Fe and Pt elements in the films became nonuniform when the annealing temperature was higher than 500 deg. C due to the formation of the Fe 3 Pt phase. After annealing at 400 deg. C, the in plane coercivity of Fe 52 Pt 48 thin film with film thickness of 100 nm is 10 kOe, M s is 580 emu/cm3, and grain size is about 12 nm

Electric and Magnetic Properties of Sputter Deposited BiFeO3 Films

Directory of Open Access Journals (Sweden)

N. Siadou

2013-01-01

Full Text Available Polycrystalline BiFeO3 films have been magnetron sputter deposited at room temperature and subsequently heat-treated ex situ at temperatures between 400 and 700°C. The deposition was done in pure Ar atmosphere, as the use of oxygen-argon mixture was found to lead to nonstoichiometric films due to resputtering effects. At a target-to-substrate distance d=2′′ the BiFeO3 structure can be obtained in larger range process gas pressures (2–7 mTorr but the films do not show a specific texture. At d=6′′ codeposition from BiFeO3 and Bi2O3 has been used. Films sputtered at low rate tend to grow with the (001 texture of the pseudo-cubic BiFeO3 structure. As the film structure does not depend on epitaxy similar results are obtained on different substrates. A result of the volatility of Bi, Bi rich oxide phases occur after heat treatment at high temperatures. A Bi2SiO5 impurity phase forms on the substrate side, and does not affect the properties of the main phase. Despite the deposition on amorphous silicon oxide substrate weak ferromagnetism phenomena and displaced loops have been observed at low temperatures showing that their origin is not strain. Ba, La, Ca, and Sr doping suppress the formation of impurity phases and leakage currents.

Growth, structure and magnetic properties of magnetron sputtered FePt thin films

Energy Technology Data Exchange (ETDEWEB)

Cantelli, Valentina

2010-07-01

The L1{sub 0} FePt phase belongs to the most promising hard ferromagnetic materials for high density recording media. The main challenges for thin FePt films are: (i) to lower the process temperature for the transition from the soft magnetic A1 to the hard magnetic L1{sub 0} phase, (ii) to realize c-axes preferential oriented layers independently from the substrate nature and (iii) to control layer morphology supporting the formation of FePt-L1{sub 0} selforganized isolated nanoislands towards an increase of the signal-to-noise ratio. In this study, dc magnetron sputtered FePt thin films on amorphous substrates were investigated. The work is focused on the correlation between structural and magnetic properties with respect to the influence of deposition parameters like growth mode (cosputtering vs. layer - by - layer) and the variation of the deposition gas (Ar, Xe) or pressure (0.3-3 Pa). In low-pressure Ar discharges, high energetic particle impacts support vacancies formation during layer growth lowering the phase transition temperature to (320{+-}20) C. By reducing the particle kinetic energy in Xe discharges, highly (001) preferential oriented L1{sub 0}-FePt films were obtained on a-SiO{sub 2} after vacuum annealing. L1{sub 0}-FePt nano-island formation was supported by the introduction of an Ag matrix, or by random ballistic aggregation and atomic self shadowing realized by FePt depositions at very high pressure (3 Pa). The high coercivity (1.5 T) of granular, magnetic isotropic FePt layers, deposited in Ar discharges, was measured with SQUID magnetometer hysteresis loops. For non-granular films with (001) preferential orientation the coercivity decreased (0.6 T) together with an enhancement of the out-of- plane anisotropy. Nanoislands show a coercive field close to the values obtained for granular layers but exhibit an in-plane easy axis due to shape anisotropy effects. An extensive study with different synchrotron X-ray scattering techniques, mainly

Magnetization, magnetic susceptibility, effective magnetic moment of Fe3+ ions in Bi25FeO39 ferrite

International Nuclear Information System (INIS)

Zatsiupa, A.A.; Bashkirov, L.A.; Troyanchuk, I.O.; Petrov, G.S.; Galyas, A.I.; Lobanovsky, L.S.; Truhanov, S.V.

2014-01-01

Magnetic susceptibility for ferrite Bi 25 FeO 39 is measured at 5–950 K in the magnetic field of 0.86 T. It is shown that Bi 25 FeO 39 is paramagnetic in the temperature range 5−950 K. The saturation magnetization is equal to 5.04μ B per formula unit at 5 K in a magnetic field of 10 T. It is found that at 5−300 K the effective magnetic moment of Fe 3+ ions in Bi 25 FeO 39 is equal to 5.82μ B . - Graphical abstract: The dependence of the magnetization (n, μ B ) on the magnetic field for one formula unit of Bi 25 FeO 39 at 5 K. - Highlights: • Magnetic susceptibility for Bi 25 FeO 39 is measured at 5–950 K in the magnetic field of 0.86 T. • It is shown that Bi 25 FeO 39 is paramagnetic in the temperature range 5−950 K. • The saturation magnetization is equal to 5.04μ B per formula unit at 5 K in a magnetic field of 10 T

Spin reorientation transitions of Fe/Ni/Cu(001) studied by using the depth-resolved X-ray magnetic circular dichroism technique

International Nuclear Information System (INIS)

Abe, Hitoshi; Amemiya, Kenta; Matsumura, Daiju; Kitagawa, Soichiro; Watanabe, Hirokazu; Yokoyama, Toshihiko; Ohta, Toshiaki

2006-01-01

The spin reorientation transition (SRT) of Ni/Cu(001) induced by Fe deposition was investigated using the X-ray magnetic circular dichroism (XMCD) method. In-plane magnetized Ni films (= =10ML) also exhibit a transition to in-plane by 1-2ML Fe deposition. A precise magnetic anisotropy phase diagram was obtained using a combination of wedge-shaped Ni samples and stepwise Fe deposition. Magnetic anisotropy energies in the bulk, surface and interface layers of Ni films were separately determined using the depth-resolved XMCD technique, while values in the 1ML and 2ML portions of the Fe films were obtained from the conventional XMCD measurements. The origin of the SRTs is successfully explained with a simple phenomenological layer model using the obtained magnetic anisotropy energies. es

Tandem solar cells deposited using hot-wire chemical vapor deposition

NARCIS (Netherlands)

Veen, M.K. van

2003-01-01

In this thesis, the application of the hot-wire chemical vapor deposition (HWCVD) technique for the deposition of silicon thin films is described. The HWCVD technique is based on the dissociation of silicon-containing gasses at the catalytic surface of a hot filament. Advantages of this technique

Achieving uniform layer deposition by atmospheric-pressure plasma-enhanced chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Lee, Jae-Ok [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Kang, Woo Seok, E-mail: kang@kimm.re.kr [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Department of Environment & Energy Mechanical Engineering, University of Science & Technology (UST), Daejeon 305-350 (Korea, Republic of); Hur, Min; Lee, Jin Young [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Song, Young-Hoon [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Department of Environment & Energy Mechanical Engineering, University of Science & Technology (UST), Daejeon 305-350 (Korea, Republic of)

2015-12-31

This work investigates the use of plasma-enhanced chemical vapor deposition under atmospheric pressure for achieving uniform layer formation. Electrical and optical measurements demonstrated that the counterbalance between oxygen and precursors maintained the homogeneous discharge mode, while creating intermediate species for layer deposition. Several steps of the deposition process of the layers, which were processed on a stationary stage, were affected by flow stream and precursor depletion. This study showed that by changing the flow streamlines using substrate stage motion uniform layer deposition under atmospheric pressure can be achieved. - Highlights: • Zirconium oxide was deposited by atmospheric-pressure plasma-enhanced chemical vapor deposition. • Homogeneous plasma was maintained by counterbalancing between discharge gas and precursors. • Several deposition steps were observed affected by the gas flow stream and precursor depletion. • Thin film layer was uniformly grown when the substrate underwent a sweeping motion.

Single-crystalline AlN growth on sapphire using physical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Cardenas-Valencia, Andres M., E-mail: andres.cardenas@sri.co [SRI International (United States); Onishi, Shinzo; Rossie, Benjamin [SRI International (United States)

2011-02-07

A novel technique for growing single crystalline aluminum nitride (AlN) films is presented. The novelty of the technique, specifically, comes from the use of an innovative physical vapor deposition magnetron sputtering tool, which embeds magnets into the target material. A relatively high deposition rates is achieved ({approx}0.2 {mu}m/min), at temperatures between 860 and 940 {sup o}C. The AlN, grown onto sapphire, is single-crystalline as evidenced by observation using transmission electron microscopy. Tool configuration and growth conditions are discussed, as well as a first set of other analytical results, namely, x-ray diffraction and ultraviolet-visible transmission spectrophotometry.

Vapor diffusion synthesis of rugby-shaped CoFe2O4/graphene composites as absorbing materials

International Nuclear Information System (INIS)

Zhang, Shenli; Jiao, Qingze; Hu, Ju; Li, Jingjing; Zhao, Yun; Li, Hansheng; Wu, Qin

2015-01-01

Graphical abstract: CoFe 2 O 4 rugbies/graphene composites were prepared using a vapor diffusion method followed by calcination. As-synthesized rugby-like CoFe 2 O 4 particles were distributed on the graphene sheet. PVP played a key role for the formation of rugby-shaped morphology of CoFe 2 O 4 particles. A minimum reflection loss of −39.0 dB was observed at 10.9 GHz for the CoFe 2 O 4 rugbies/graphene composites with a thickness of 2 mm, and the effective absorption bandwidth was 4.7 GHz. The CoFe 2 O 4 rugbies/graphene composites exhibited better microwave absorbing performance than that of the CoFe 2 O 4 nanoparticles/graphene composites prepared without PVP. - Highlights: • CoFe 2 O 4 rugbies/graphene hybrids were synthesized using a vapor diffusion method. • PVP played a key role for the formation of CoFe 2 O 4 rugbies. • CoFe 2 O 4 rugbies/graphene composites showed excellent microwave absorbing property. - Abstract: Rugby-shaped CoFe 2 O 4 /graphene composites were synthesized using a vapor diffusion method in combination with calcination. The morphologies and structures of the products were characterized by field emission scanning electron microscopy, X-ray diffractometer, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. Results show that rugby-shaped CoFe 2 O 4 particles are distributed on graphene sheets. A minimum reflection loss (RL) of −39.0 dB is observed at 10.9 GHz for the sample with a thickness of 2.0 mm, and the effective absorption frequency (RL < −10 dB) ranges from 9.6 to 14.3 GHz, indicating the excellent microwave absorption performance of the products. The absorbing performance of the CoFe 2 O 4 rugbies/graphene composites is better than that of the CoFe 2 O 4 nanoparticles/graphene composites

Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

International Nuclear Information System (INIS)

Kumar, Santosh; Deepika; Tripathi, Malvika; Vaibhav, Pratyush; Kumar, Aman; Kumar, Ritesh; Choudhary, R.J.; Phase, D.M.

2016-01-01

The structural, magnetic and magneto-transport of undoped ZnO, Zn_0_._9_7Al_0_._0_3O, Zn_0_._9_5Fe_0_._0_5O and Zn_0_._9_2Al_0_._0_3Fe_0_._0_5O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

Energy Technology Data Exchange (ETDEWEB)

Kumar, Santosh, E-mail: skphysics@yahoo.co.in [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Deepika [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Tripathi, Malvika [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Vaibhav, Pratyush [Jaypee University of Engineering and Technology, Guna 473226, Madhya Pradesh (India); Kumar, Aman [Indian Institute of Technology, Roorkee (India); Kumar, Ritesh [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Choudhary, R.J., E-mail: ram@csr.res.in [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Phase, D.M. [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India)

2016-12-01

The structural, magnetic and magneto-transport of undoped ZnO, Zn{sub 0.97}Al{sub 0.03}O, Zn{sub 0.95}Fe{sub 0.05}O and Zn{sub 0.92}Al{sub 0.03}Fe{sub 0.05}O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

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

Ti-doped hydrogenated diamond like carbon coating deposited by hybrid physical vapor deposition and plasma enhanced chemical vapor deposition

Science.gov (United States)

Lee, Na Rae; Sle Jun, Yee; Moon, Kyoung Il; Sunyong Lee, Caroline

2017-03-01

Diamond-like carbon films containing titanium and hydrogen (Ti-doped DLC:H) were synthesized using a hybrid technique based on physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). The film was deposited under a mixture of argon (Ar) and acetylene gas (C2H2). The amount of Ti in the Ti-doped DLC:H film was controlled by varying the DC power of the Ti sputtering target ranging from 0 to 240 W. The composition, microstructure, mechanical and chemical properties of Ti-doped DLC:H films with varying Ti concentrations, were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nano indentation, a ball-on-disk tribometer, a four-point probe system and dynamic anodic testing. As a result, the optimum composition of Ti in Ti-doped DLC:H film using our hybrid method was found to be a Ti content of 18 at. %, having superior electrical conductivity and high corrosion resistance, suitable for bipolar plates. Its hardness value was measured to be 25.6 GPa with a low friction factor.

Strong 3D and 1D magnetism in hexagonal Fe-chalcogenides FeS and FeSe vs. weak magnetism in hexagonal FeTe.

Science.gov (United States)

Parker, David S

2017-06-13

We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large T c value is unlikely.

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

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

Magnetic and Electrical Properties of Nitrogen-Doped Multiwall Carbon Nanotubes Fabricated by a Modified Chemical Vapor Deposition Method

Directory of Open Access Journals (Sweden)

María Luisa García-Betancourt

2015-01-01

Full Text Available Chemical vapor deposition (CVD is a preferential method to fabricate carbon nanotubes (CNTs. Several changes have been proposed to obtain improved CNTs. In this work we have fabricated nitrogen-doped multiwall carbon nanotubes (N-MWCNTs by means of a CVD which has been slightly modified. Such modification consists in changing the content of the by-product trap. Instead of acetone, we have half-filled the trap with an aqueous solution of NaCl (0–26.82 wt.%. Scanning electron microscope (SEM characterization showed morphological changes depending upon concentration of NaCl included in the trap. Using high resolution transmission electron microscopy several shape changes on the catalyst nanoparticles were also observed. According to Raman spectroscopy results N-MWCNTs fabricated using pure distillate water exhibit better crystallinity. Resistivity measurements performed on different samples by physical properties measurement Evercool system (PPMS showed metallic to semiconducting temperature dependent transitions when high content of NaCl is used. Results of magnetic properties show a ferromagnetic response to static magnetic fields and the coercive fields were very similar for all the studied cases. However, saturation magnetization is decreased if aqueous solution of NaCl is used in the trap.

Fabrication and properties of iron-based soft magnetic composites coated with parylene via chemical vapor deposition polymerization

International Nuclear Information System (INIS)

Wu, Shen; Sun, Aizhi; Lu, Zhenwen; Cheng, Chuan

2015-01-01

This paper focuses on novel iron-based soft magnetic composites synthesis utilizing low friction factor parylene C films to coat iron powder via chemical vapor deposition polymerization. The morphology, magnetic properties, density, and chemical stability of parylene insulated iron particles were investigated. The coated parylene insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The thickness of parylene C film is averagely 300 nm according to the results of transmission electron microscopy. Parylene C film uniformly coated the powder surface resulting in reducing the permeability imaginary part, increasing electrical resistivity and increasing the operating frequency of the synthesized magnets. It was shown that the parylene C coated compacts exhibited noticeably higher density compared to the epoxy resin coated compacts at the same pressure, suppress at 800 MPa increased the density by 17.02%. The result of Tafel curves indicated that the resistance of the iron particles to corrosion by NaCl solution is obviously improved after being insulated with parylene C film. - Highlights: • Parylene C uniformly coated the powder, increased the operating frequency of SMCs. • Compared with epoxy coated, the density of SMCs increased by 17.02% at 800 MPa. • The resistance of the iron particles is obviously improved with parylene film insulated

Magnetic studies in evaporated Ni/Pd multilayers

International Nuclear Information System (INIS)

Chafai, K.; Salhi, H.; Lassri, H.; Yamkane, Z.; Lassri, M.; Abid, M.; Hlil, E.K.; Krishnan, R.

2011-01-01

The magnetic properties of Ni/Pd multilayers, prepared by sequential evaporation in ultrahigh vacuum, have been studied. The Ni thickness dependence of the magnetization and magnetic anisotropy is discussed. The temperature dependence of the spontaneous magnetization is well described by a T 3/2 law in all multilayers. A spin-wave theory has been used to explain the temperature dependence of the spontaneous magnetization, and the approximate values for the exchange interactions for various Ni layer thicknesses have been obtained. - Research highlights: → The magnetic properties of Ni/Pd multilayers, prepared by sequential evaporation in ultrahigh vacuum, have been studied. → The temperature dependence of the spontaneous magnetization is well described by a T 3/2 law in Ni/Pd multilayers. → The spin-wave constant B was observed to depend on t Ni nonmonotonically. → A spin-wave theory has been used to explain the temperature dependence of the spontaneous magnetization. → The approximate values for the exchange interactions for various Ni layer thicknesses have been obtained.

Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

KAUST Repository

Song, Hyon Min; Zink, Jeffrey I.; Khashab, Niveen M.

2015-01-01

supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary

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.

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.)

Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

Energy Technology Data Exchange (ETDEWEB)

Mao Shoudong; Yang Hengxiu; Li Jinlong; Huang Feng [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 519 Zhuangshi Road, Ningbo 315201 (China); Song Zhenlun, E-mail: songzhenlun@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 519 Zhuangshi Road, Ningbo 315201 (China)

2011-04-15

Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar{sup +} ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar{sup +} ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.

Strong 3D and 1D magnetism in hexagonal Fe-chalcogenides FeS and FeSe vs. weak magnetism in hexagonal FeTe

Energy Technology Data Exchange (ETDEWEB)

Parker, David S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-06-13

We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large T_c value is unlikely.

Effects of etchants in the transfer of chemical vapor deposited graphene

Science.gov (United States)

Wang, M.; Yang, E. H.; Vajtai, R.; Kono, J.; Ajayan, P. M.

2018-05-01

The quality of graphene can be strongly modified during the transfer process following chemical vapor deposition (CVD) growth. Here, we transferred CVD-grown graphene from a copper foil to a SiO2/Si substrate using wet etching with four different etchants: HNO3, FeCl3, (NH4)2S2O8, and a commercial copper etchant. We then compared the quality of graphene after the transfer process in terms of surface modifications, pollutions (residues and contaminations), and electrical properties (mobility and density). Our tests and analyses showed that the commercial copper etchant provides the best structural integrity, the least amount of residues, and the smallest doping carrier concentration.

Comparison of a model vapor deposited glass films to equilibrium glass films

Science.gov (United States)

Flenner, Elijah; Berthier, Ludovic; Charbonneau, Patrick; Zamponi, Francesco

Vapor deposition of particles onto a substrate held at around 85% of the glass transition temperature can create glasses with increased density, enthalpy, kinetic stability, and mechanical stability compared to an ordinary glass created by cooling. It is estimated that an ordinary glass would need to age thousands of years to reach the kinetic stability of a vapor deposited glass, and a natural question is how close to the equilibrium is the vapor deposited glass. To understand the process, algorithms akin to vapor deposition are used to create simulated glasses that have a higher kinetic stability than their annealed counterpart, although these glasses may not be well equilibrated either. Here we use novel models optimized for a swap Monte Carlo algorithm in order to create equilibrium glass films and compare their properties with those of glasses obtained from vapor deposition algorithms. This approach allows us to directly assess the non-equilibrium nature of vapor-deposited ultrastable glasses. Simons Collaboration on Cracking the Glass Problem and NSF Grant No. DMR 1608086.

How to obtain a magnetic hard-soft architecture by pulsed laser deposition

International Nuclear Information System (INIS)

Fix, T; Trassin, M; Hassan, R Sayed; Schmerber, G; Viart, N; Meny, C; Colis, S; Dinia, A

2007-01-01

In spin valve type systems, one ferromagnetic electrode must be magnetically hard to act as a reference layer while the other electrode must be magnetically soft to act as a sensor or storage layer. This magnetic hard-soft architecture can usually be obtained by four different methods: the use of two ferromagnets with different coercive fields (here CoFe 2 and Ni 80 Fe 20 ), the use of an underlayer enhancing the coercive field of one of the two ferromagnets (here Ta and Ru), the use of a ferromagnet coupled to a ferrimagnet or antiferromagnet (here NiO/CoFe 2 and CoFe 2 O 4 /CoFe 2 ), or the use of an artificial antiferromagnet (here CoFe 2 /Ru/CoFe 2 ). We show that at least the first and the third methods seem to work with pulsed laser deposition in the thermodynamic conditions used

Microwave characteristics of low density flaky magnetic particles

International Nuclear Information System (INIS)

Wenqiang, Zhang; Deyuan, Zhang; Jun, Cai

2013-01-01

Diatomite coated with thin Fe films were obtained by the Chemical Vapor Deposition process. The resultant Fe-coated flaky diatomite particles had low densities (2.7–4.0 g/cm 3 ) and high saturation magnetization (93–157 emu/g). Annealing treatment led to grain growth and an increased saturation magnetization. The high frequency properties of the composites consisting of Fe-coated flaky diatomite particles and wax were investigated. The permittivity and permeability increased with increasing flaky magnetic particles content in the composite and increasing the Fe weight percentage of the particles. The reflection loss of the composite was found dependent on the absorber material thickness, wax:flaky magnetic particles ratios, the Fe content, as well as the annealing treatment. At a thickness of 1 mm, the composite records a minimum reflection loss of −18 dB at 6 GHz. - Highlights: ► We synthesize the flaky magnetic particles with the diatomite as template. ► The flaky magnetic particles coating layers are constituted by α-Fe. ► The flaky magnetic particles have good static magnetic properties. ► The flaky magnetic particles are a kind light weight high performance microwave absorber

Microwave characteristics of low density flaky magnetic particles

Energy Technology Data Exchange (ETDEWEB)

Wenqiang, Zhang, E-mail: zwqzwqzwqzwq@126.com [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China); College of Engineering, China Agricultural University, Beijing 100083 (China); Deyuan, Zhang [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China); Jun, Cai, E-mail: jun_cai@buaa.edu.cn [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China)

2013-04-15

Diatomite coated with thin Fe films were obtained by the Chemical Vapor Deposition process. The resultant Fe-coated flaky diatomite particles had low densities (2.7–4.0 g/cm{sup 3}) and high saturation magnetization (93–157 emu/g). Annealing treatment led to grain growth and an increased saturation magnetization. The high frequency properties of the composites consisting of Fe-coated flaky diatomite particles and wax were investigated. The permittivity and permeability increased with increasing flaky magnetic particles content in the composite and increasing the Fe weight percentage of the particles. The reflection loss of the composite was found dependent on the absorber material thickness, wax:flaky magnetic particles ratios, the Fe content, as well as the annealing treatment. At a thickness of 1 mm, the composite records a minimum reflection loss of −18 dB at 6 GHz. - Highlights: ► We synthesize the flaky magnetic particles with the diatomite as template. ► The flaky magnetic particles coating layers are constituted by α-Fe. ► The flaky magnetic particles have good static magnetic properties. ► The flaky magnetic particles are a kind light weight high performance microwave absorber.

Synthesis, characterization and magnetic properties of Fe-Al nanopins

International Nuclear Information System (INIS)

Zhang, W.S.; Brueck, E.; Li, W.F.; Si, P.Z.; Geng, D.Y.; Zhang, Z.D.

2005-01-01

We report the synthesis of Fe-Al nanopins using arc discharge. The morphology and chemical composition of the Fe-Al nanopins were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). The nanopins are composed of a spherical base of about 20-100 nm and a needle-like tip of about several hundred nanometers. EDX and HRTEM studies indicate that the spherical base is mainly composed of α-Fe and FeAl core coated with a thin Al 2 O 3 layer, while the needle-like part contains only Al and O and corresponds to Al 2 O 3 . The formation mechanism of the nanopins is suggestive of a vapor-liquid-solid (VLS) growth process. The as-prepared Fe-Al nanopins show ferromagnetic properties. The temperature dependence of the magnetization at high temperatures indicates the existence of some phase transformations

Dispersion of carbon nanotubes in hydroxyapatite powder by in situ chemical vapor deposition

International Nuclear Information System (INIS)

Li Haipeng; Wang Lihui; Liang, Chunyong; Wang Zhifeng; Zhao Weimin

2010-01-01

In the present work, we use chemical vapor deposition of methane to disperse carbon nanotubes (CNTs) within hydroxyapatite (HA) powder. The effect of different catalytic metal particles (Fe, Ni or Co) on the morphological and structural development of the powder and dispersion of CNTs in HA powder was investigated. The results show that the technique is effective in dispersing the nanotubes within HA powder, which simultaneously protects the nanotubes from damage. The results can have important and promising speculations for the processing of CNT-reinforced HA-matrix composites in general.

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

MAGNETIC VISCOSITY IN NdFeB MAGNETS

OpenAIRE

Martinez , J.; Missell , F.

1988-01-01

The relaxation of the magnetization is calculated for isotropic and anisotropic magnets. For NdFeB magnets, the dependence of Sv on texture, above room temperature, is roughly consistent with the model, while the NdDyFeB magnets show no dependence upon texture.

Coercivity enhancement of sintered Nd-Fe-B magnets by chemical bath deposition of TbCl{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Guo, Shuai, E-mail: gshuai@nimte.ac.cn; Zhang, Xiaofeng; Ding, Guangfei; Chen, Renjie; Yan, Aru [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Lee, Don [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); University of Dayton, Dayton, Ohio 45469 (United States)

2014-05-07

The chemical bath deposition (CBD) and the grain boundary diffusion method were combined to diffuse the heavy rare earth for obtain the thick magnets with high coercivity and low heavy rare earth. The jet mill powders were soaked into the alcohol solution of 0.2 wt. % TbCl{sub 3}. A thin layer of TbCl{sub 3} was wrapped to the surface of (PrNd){sub 2}Fe{sub 14}B powder particles. The coercivity of magnet is increased from 11.89 kOe to 14.72 kOe without significant reduction of remanence after grain boundary diffusion in the sintering and the annealing processes. The temperature coefficients of the remanence and the coercivity are improved by the substitution of PrNd by Tb in the surface of grains. The highly accelerated temperature/humidity stress test (HAST) results indicate that the CBD magnet has poor corrosion resistance, attributing to the present of Cl atoms in the grain boundaries.

CuFeO2 formation using fused deposition modeling 3D printing and sintering technique

Science.gov (United States)

Salea, A.; Dasaesamoh, A.; Prathumwan, R.; Kongkaew, T.; Subannajui, K.

2017-09-01

CuFeO2 is a metal oxide mineral material which is called delafossite. It can potentially be used as a chemical catalyst, and gas sensing material. There are methods to fabricate CuFeO2 such as chemical synthesis, sintering, sputtering, and chemical vapor deposition. In our work, CuFeO2 is prepared by Fused Deposition Modeling (FDM) 3D printing. The composite filament which composed of Cu and Fe elements is printed in three dimensions, and then sintered and annealed at high temperature to obtain CuFeO2. Suitable polymer blend and maximum percent volume of metal powder are studied. When percent volume of metal powder is increased, melt flow rate of polymer blend is also increased. The most suitable printing condition is reported and the properties of CuFeO2 are observed by Scanning Electron Microscopy, and Dynamic Scanning Calorimeter, X-ray diffraction. As a new method to produce semiconductor, this technique has a potential to allow any scientist or students to design and print a catalyst or sensing material by the most conventional 3D printing machine which is commonly used around the world.

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.

Silver doped hydroxyapatite coatings by sacrificial anode deposition under magnetic field.

Science.gov (United States)

Swain, S; Rautray, T R

2017-09-13

Uniform distribution of silver (Ag) in the hydroxyapatite (HA) coated Ti surface has been a concern for which an attempt has been made to dope Ag in HA coating with and without magnetic field. Cathodic deposition technique was employed to coat Ag incorporated hydroxyapatite coating using a sacrificial silver anode method by using NdFeB bar magnets producing 12 Tesla magnetic field. While uniform deposition of Ag was observed in the coatings under magnetic field, dense coating was evident in the coating without magnetic field conditions. Uniformly distributed Ag incorporated HA in the present study has potential to fight microorganism while providing osseoconduction properties of the composite coating.

Structural and physical properties of new uranium and transition element ternary stannides (Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt); Proprietes structurales et physiques de nouveaux stannures ternaires a base d'uranium et d'element de transition (Fe, Co, Ni, Rh, Pd, Ir, Pt)

Energy Technology Data Exchange (ETDEWEB)

Mirambet, F

1993-12-15

This work is dedicated to the study of ternary stannides based on uranium. The author reviews the structural, magnetic and electric properties of different families of stannides. The study of the U{sub 2}M{sub 2}Sn family where M stands for Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt shows that the magnetic behaviour of uranium in these compounds is strongly influenced by the transition element M, which is explained by the hybridization force 5f(U) - nd(M) that depends on the number of electrons on the d shell of the M element. For instance, for the elements whose d shell is low filled (Fe, Ru), the U{sub 2}M{sub 2}Sn stannides show no magnetic order. On the other hand, when the number of d-electrons increases, a magnetic order appears progressively.

A comprehensive study of ferromagnetic resonance and structural properties of iron-rich nickel ferrite (Ni{sub x}Fe{sub 3−x}O{sub 4}, x≤1) films grown by chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Pachauri, Neha; Khodadadi, Behrouz [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Singh, Amit V. [Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Mohammadi, Jamileh Beik [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Martens, Richard L. [Central Analytical Facility (CAF), The University of Alabama, Tuscaloosa, Alabama 35487 (United States); LeClair, Patrick R.; Mewes, Claudia; Mewes, Tim [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama 35487 (United States); Gupta, Arunava [Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, Alabama 35487 (United States)

2016-11-01

We report a detailed study of the structural and ferromagnetic resonance properties of spinel nickel ferrite (NFO) films, grown on (100)-oriented cubic MgAl{sub 2}O{sub 4} substrates by direct liquid injection chemical vapor deposition (DLI-CVD) technique. Three different compositions of NFO films (Ni{sub x}Fe{sub 3−x}O{sub 4} where x=1, 0.8, 0.6) deposited at optimized growth temperature of 600 °C are characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometry (VSM), and broadband ferromagnetic resonance (FMR) techniques. XRD confirms the growth of epitaxial, single crystalline Ni{sub x}Fe{sub 3−x}O{sub 4} films. The out-of-plane lattice constant (c) obtained for Ni{sub 0.8}Fe{sub 2.2}O{sub 4} film is slightly higher than the bulk value (0.833 nm), indicating only partial strain relaxation whereas for the other two compositions (x=1 and x=0.6) films exhibit complete relaxation. The in-plane and out-of-plane FMR linewidths measurements at 10 GHz give the lowest values of 458 Oe and 98 Oe, respectively, for Ni{sub 0.8}Fe{sub 2.2}O{sub 4} film as compared to the other two compositions. A comprehensive frequency (5–40 GHz) and temperature (10–300 K) dependent FMR study of the Ni{sub 0.8}Fe{sub 2.2}O{sub 4} sample for both in-lane and out-of-plane configurations reveals two magnon scattering (TMS) as the dominant in-plane relaxation mechanism. It is observed that the TMS contribution to the FMR linewidth scales with the saturation magnetization M{sub s}. In-plane angle-dependent FMR measurements performed on the same sample show that the ferromagnetic resonance field (H{sub res}) and the FMR linewidth (ΔH) have a four-fold symmetry that is consistent with the crystal symmetry of the spinel. SEM measurements show formation of pyramid-like microstructures at the surface of the Ni{sub 0.8}Fe{sub 2.2}O{sub 4} sample, which can explain the observed four-fold symmetry of the FMR linewidth.

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.

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.

Epitaxial stabilization of ordered Pd–Fe structures on perovskite substrates

Energy Technology Data Exchange (ETDEWEB)

Harton, Renee M., E-mail: reneehar@umich.edu [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States); Stoica, Vladimir A. [Department of Materials Science and Engineering, Pennsylvania State University, 201 Old Main, University Park, PA 16802 (United States); Clarke, Roy [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States)

2017-05-01

We report the fabrication of epitaxial ferromagnetic Pd{sub 3}Fe thin films on SrTiO{sub 3}(001) substrates by promoting the interdiffusion of an Fe/Pd multilayer heterostructure using thermal annealing. Prior to annealing, the results of in-situ Reflection High-Energy Electron Diffraction characterization suggest that each Fe and Pd layer exhibited an in-plane epitaxial relationship with the SrTiO{sub 3}(001) substrate. X-Ray diffraction and magneto-optic Kerr effect characterization, conducted post-annealing, demonstrate that the film composition is majority Pd{sub 3}Fe and exhibits in-plane magnetization reversal with a moderate coercive field of ≈760 Oe. This demonstration of an ordered atomic layer heterostructure grown on a perovskite substrate suggests a route to epitaxial interfacial structures which can achieve strain-assisted magnetic switching.

An efficient fabrication of vertically aligned carbon nanotubes on flexible aluminum foils by catalyst-supported chemical vapor deposition

International Nuclear Information System (INIS)

Yoshikawa, Naoki; Kishi, Naoki; Sugai, Toshiki; Shinohara, Hisanori; Asari, Takuma; Hayashi, Shigeo

2008-01-01

An efficient and versatile growth of thin-layer carbon nanotubes on a flexible aluminum foil (for kitchen use) by catalyst-supported chemical vapor deposition is reported. The aluminum foil used in the present experiment is commercially available for kitchen use. The electron-beam vapor deposition and dip-coating have been used for preparing catalysts on the aluminum foil. Vertically aligned thin-layer CNTs with typical diameters of 2.5-6.0 nm and lengths up to 90 μm are obtained when ethanol is used in combination with Fe and Co catalyst particles at a growth temperature of around 650 deg. C under an Ar/H 2 gas flow. Thermo-gravimetric analyses together with HR-TEM observations indicate that the purity of the CNTs synthesized by the current technique is very high

Comparative electrocatalytic oxidation of ethanol, ethylene glycol and glycerol in alkaline medium at Pd-decorated FeCo@Fe/C core-shell nanocatalysts

CSIR Research Space (South Africa)

Fashedemi, OO

2014-05-01

Full Text Available ) were explored, and compared with those of the Pd/C alone. FeCo@Fe@Pd/C exhibited a remarkable performance in all three alcohols but its best electrocatalytic activity was found in the oxidation of EG where the electrocatalytic rate constant (K...

Magnetic properties of electroplated nano/microgranular NiFe thin films for rf application

NARCIS (Netherlands)

Zhuang, Y.; Vroubel, M.; Rejaei, B.; Burghartz, J.N.; Attenborough, K.

2005-01-01

A granular NiFe thin film with large in-plane magnetic anisotropy and high ferromagnetic-resonance frequency developed for radio-frequency integrated circuit (IC) applications is presented. During the deposition, three-dimensional (3D) growth occurs, yielding NiFe grains (? ? 1.0??m). Nanonuclei (?

CoFe Layers Thickness and Annealing Effect on the Magnetic Behavior of the CoFe/Cu Multilayer Nanowires

Directory of Open Access Journals (Sweden)

M. Ahmadzadeh

2015-04-01

Full Text Available CoFe/Cu multilayer nanowires were electrodeposited into anodic aluminum oxide templates prepared by a two-step mild anodization method, using the single-bath technique. Nanowires with 30 nm diameter and the definite lengths were obtained. The effect of CoFe layers thickness and annealing on the magnetic behavior of the multilayer nanowires was investigated. The layers thickness was controlled through the pulses numbers: 200, 260, 310,360 and 410 pulses were used to deposit the CoFe layers, while 300 pulse for the Cu layers. A certain increase in coercivity and squareness of CoFe/Cu multilayer nanowires observed with increasing the CoFe layer thickness and annealing improved the coercivity and decrease squareness of CoFe/Cu multilayer nanowires. First order reversal curves after annealed showed amount domains with soft magnetic phase, it also shows decreasing spreading of distribution function along the Hu axis after annealed

Selective metal-vapor deposition on solvent evaporated polymer surfaces

Energy Technology Data Exchange (ETDEWEB)

Yamaguchi, Koji; Tsujioka, Tsuyoshi, E-mail: tsujioka@cc.osaka-kyoiku.ac.jp

2015-12-31

We report a selective metal-vapor deposition phenomenon based on solvent printing and evaporation on polymer surfaces and propose a method to prepare fine metal patterns using maskless vacuum deposition. Evaporation of the solvent molecules from the surface caused large free volumes between surface polymer chains and resulted in high mobility of the chains, enhancing metal-vapor atom desorption from the surface. This phenomenon was applied to prepare metal patterns on the polymer surface using solvent printing and maskless metal vacuum deposition. Metal patterns with high resolution of micron scale were obtained for various metal species and semiconductor polymer substrates including poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] and poly(3-hexylthiophene-2,5-diyl). - Highlights: • Selective metal-vapor deposition using solvent evaporation on polymer was attained. • Metal patterns with high resolution were obtained for various metal species. • This method can be applied to achieve fine metal-electrodes for polymer electronics.

High performance hard magnetic NdFeB thick films for integration into micro-electro-mechanical systems

International Nuclear Information System (INIS)

Dempsey, N. M.; Walther, A.; May, F.; Givord, D.; Khlopkov, K.; Gutfleisch, O.

2007-01-01

5 μm thick NdFeB films have been sputtered onto 100 mm Si substrates using high rate sputtering (18 μm/h). Films were deposited at ≤500 deg. C and then annealed at 750 deg. C for 10 min. While films deposited at temperatures up to 450 deg. C have equiaxed grains, the size of which decreases with increasing deposition temperature, the films deposited at 500 deg. C have columnar grains. The out-of-plane remanent magnetization increases with deposition temperature, reaching a maximum value of 1.4 T, while the coercivity remains constant at about 1.6 T. The maximum energy product achieved (400 kJ/m 3 ) is comparable to that of high-quality NdFeB sintered magnets

Control of microstructure in soldered, brazed, welded, plated, cast or vapor deposited manufactured components

Science.gov (United States)

Ripley, Edward B.; Hallman, Russell L.

2015-11-10

Disclosed are methods and systems for controlling of the microstructures of a soldered, brazed, welded, plated, cast, or vapor deposited manufactured component. The systems typically use relatively weak magnetic fields of either constant or varying flux to affect material properties within a manufactured component, typically without modifying the alloy, or changing the chemical composition of materials or altering the time, temperature, or transformation parameters of a manufacturing process. Such systems and processes may be used with components consisting of only materials that are conventionally characterized as be uninfluenced by magnetic forces.

Perpendicular magnetic anisotropy of CoFeB\\Ta bilayers on ALD HfO2

Directory of Open Access Journals (Sweden)

Bart F. Vermeulen

2017-05-01

Full Text Available Perpendicular magnetic anisotropy (PMA is an essential condition for CoFe thin films used in magnetic random access memories. Until recently, interfacial PMA was mainly known to occur in materials stacks with MgO\\CoFe(B interfaces or using an adjacent crystalline heavy metal film. Here, PMA is reported in a CoFeB\\Ta bilayer deposited on amorphous high-κ dielectric (relative permittivity κ=20 HfO2, grown by atomic layer deposition (ALD. PMA with interfacial anisotropy energy Ki up to 0.49 mJ/m2 appears after annealing the stacks between 200°C and 350°C, as shown with vibrating sample magnetometry. Transmission electron microscopy shows that the decrease of PMA starting from 350°C coincides with the onset of interdiffusion in the materials. High-κ dielectrics are potential enablers for giant voltage control of magnetic anisotropy (VCMA. The absence of VCMA in these experiments is ascribed to a 0.6 nm thick magnetic dead layer between HfO2 and CoFeB. The results show PMA can be easily obtained on ALD high-κ dielectrics.

Micro-patterning of NdFeB and SmCo magnet films for integration into micro-electro-mechanical-systems

International Nuclear Information System (INIS)

Walther, A.; Marcoux, C.; Desloges, B.; Grechishkin, R.; Givord, D.; Dempsey, N.M.

2009-01-01

The integration of high-performance RE-TM (NdFeB and SmCo) hard magnetic films into micro-electro-mechanical-systems (MEMS) requires their patterning at the micron scale. In this paper we report on the applicability of standard micro-fabrication steps (film deposition onto topographically patterned substrates, wet etching and planarization) to the patterning of 5-8 μm thick RE-TM films. While NdFeB comprehensively fills micron-scaled trenches in patterned substrates, SmCo deposits are characterized by poor filling of the trench corners, which poses a problem for further processing by planarization. The magnetic hysteresis loops of both the NdFeB and SmCo patterned films are comparable to those of non-patterned films prepared under the same deposition/annealing conditions. A micron-scaled multipole magnetic field pattern is directly produced by the unidirectional magnetization of the patterned films. NdFeB and SmCo show similar behavior when wet etched in an amorphous state: etch rates of approximately 1.25 μm/min and vertical side walls which may be attributed to a large lateral over-etch of typically 20 μm. Chemical-mechanical-planarization (CMP) produced material removal rates of 0.5-3 μm/min for amorphous NdFeB. Ar ion etching of such films followed by the deposition of a Ta layer prior to film crystallization prevented degradation in magnetic properties compared to non-patterned films

Micro-patterning of NdFeB and SmCo magnet films for integration into micro-electro-mechanical-systems

Energy Technology Data Exchange (ETDEWEB)

Walther, A. [CEA Leti-MINATEC, 17 rue des Martyrs, 38054 Grenoble (France); Institut Neel, CNRS-UJF, 25 rue des Martyrs, 38042 Grenoble (France); Marcoux, C.; Desloges, B. [CEA Leti-MINATEC, 17 rue des Martyrs, 38054 Grenoble (France); Grechishkin, R. [Laboratory of Magnetoelectronics, Tver State University, 170000 Tver (Russian Federation); Givord, D. [Institut Neel, CNRS-UJF, 25 rue des Martyrs, 38042 Grenoble (France); Dempsey, N.M. [Institut Neel, CNRS-UJF, 25 rue des Martyrs, 38042 Grenoble (France)], E-mail: nora.dempsey@grenoble.cnrs.fr

2009-03-15

The integration of high-performance RE-TM (NdFeB and SmCo) hard magnetic films into micro-electro-mechanical-systems (MEMS) requires their patterning at the micron scale. In this paper we report on the applicability of standard micro-fabrication steps (film deposition onto topographically patterned substrates, wet etching and planarization) to the patterning of 5-8 {mu}m thick RE-TM films. While NdFeB comprehensively fills micron-scaled trenches in patterned substrates, SmCo deposits are characterized by poor filling of the trench corners, which poses a problem for further processing by planarization. The magnetic hysteresis loops of both the NdFeB and SmCo patterned films are comparable to those of non-patterned films prepared under the same deposition/annealing conditions. A micron-scaled multipole magnetic field pattern is directly produced by the unidirectional magnetization of the patterned films. NdFeB and SmCo show similar behavior when wet etched in an amorphous state: etch rates of approximately 1.25 {mu}m/min and vertical side walls which may be attributed to a large lateral over-etch of typically 20 {mu}m. Chemical-mechanical-planarization (CMP) produced material removal rates of 0.5-3 {mu}m/min for amorphous NdFeB. Ar ion etching of such films followed by the deposition of a Ta layer prior to film crystallization prevented degradation in magnetic properties compared to non-patterned films.

Growth, structure and magnetic properties of single crystalline Fe/CoO/Ag(001) bilayers

Energy Technology Data Exchange (ETDEWEB)

Abrudan, R.M.

2007-07-16

The structural and magnetic properties of epitaxially deposited single-crystalline CoO layers and Fe/CoO bilayers on Ag(001) were investigated. CoO films on Ag(001) exhibit (1 x 1) Low Energy Electron Diffraction (LEED) patterns similar to the clean Ag(001) substrate. The vertical interlayer spacing of the CoO films, deduced from a kinematic analysis of LEED I(E) curves, is a {sub perpendicular} {sub to} /2=2.17 Aa, slightly expanded along the film normal. Scanning Tunneling Microscopy (STM) show a big improvement in the surface roughness after annealing the CoO films at 750 K in oxygen atmosphere. Magnetic measurements using the magneto-optical Kerr effect (MOKE) show a characteristic increase of the coercive field when the Fe/CoO bilayer system is cooled down from room temperature to 150 K. The ordering temperature for the antiferromagnetic layer is in the same range as the Neel temperature for bulk CoO (T{sub N}=290 K). X-ray absorption spectroscopy was employed to probe magnetic and electronic properties with elemental selectivity. Absorption spectra taken from bilayers with different amounts of deposited Fe show only a weak indication for the formation of Fe oxide at the Fe/CoO interface (0.3 ML Fe). From the spectral shape it is concluded that an FeO type of oxide is formed. X-ray Magnetic Circular Dichroism (XMCD) measurements exhibit a sizeable induced ferromagnetic signal at the Co L{sub 2,3} absorption edge, corresponding to an interface layer of 1.1 ML in which the magnetic spins couple with the Fe layer. The angular dependence of the X-ray Magnetic Linear Dichroism (XMLD) and X-ray Magnetic Circular Dichroism XMCD at both the Co and Fe L{sub 2,3} edges shows the orientation of the Co and Fe moments in the bilayers with respect to the crystallographic direction. PhotoElectron Emission Microscope (PEEM) is used to image each ferromagnetic and antiferromagnetic layer separately. Magnetic contrast due to the induced magnetic spins at the interface is also

Chemical vapor deposition of diamond onto iron based substrates. The use of barrier layers

International Nuclear Information System (INIS)

Weiser, P.S.; Prawer, S.

1995-01-01

When Fe is exposed to the plasma environment suitable for the chemical vapor deposition (CVD) of diamond, the surface is rapidly covered with a thick layer graphitic soot and C swiftly diffuses into the Fe substrate. Once the soot reaches a critical thickness, diamond films nucleate and grow on top of it. However, adhesion of the film to the substrate is poor due to the lack of structural integrity of the soot layer, A thin coating of TiN on the Fe can act to prevent diffusion and soot formation. Diamond readily grows upon the TiN via an a-C interface layer, but the a-C/TiN interface is weak and delamination occurs at this interface. In order to try and improve the adhesion, the use of a high dose Ti implant was investigated to replace the TiN coating. 7 refs., 6 figs

Fabrication of Vertically Aligned CNT Composite for Membrane Applications Using Chemical Vapor Deposition through In Situ Polymerization

Directory of Open Access Journals (Sweden)

Munir Mohammad

2013-01-01

Full Text Available We report the fabrication of vertically aligned carbon nanotubes (CNT composite using thermal chemical vapor deposition (CVD. A forest of vertically aligned CNTs was grown using catalytic CVD. Fluorocarbon polymer, films were deposited in the spaces between vertically aligned MWCNTs using thermal CVD apparatus developed in-house. The excessive polymer top layer was etched by exposing the sample to water plasma. Infrared spectroscopy confirmed the attachment of functional groups to CNTs. Alignment of CNTs, deposition of polymer and postetched specimens were analyzed by field emission scanning electron microscope (FE-SEM. Uniform distribution of monomodel vertically aligned CNTs embedded in the deposited polymer matrix was observed in the micrograph. Observed uniform distribution otherwise is not possible using conventional techniques such as spin coating.

Adsorption induced modification of in-plane magnetic anisotropy in epitaxial Co and Fe/Co films on Fe(110)

Science.gov (United States)

Ślezak, M.; Ślezak, T.; Matlak, K.; DróŻdŻ, P.; Korecki, J.

2018-05-01

A study of in-plane magnetic anisotropy (MA) in epitaxial bcc Co films and Fe/Co bilayers on a Fe(110) surface is reported. Surface MA of as-deposited Co films and Fe/Co bilayers strongly depends on the Co (dCo) and Fe (dFe) thickness. Adsorption of residual gases drastically modifies in-plane MA of both Co films and Fe/Co bilayers. We present two dimensional MA maps in the (dCo, dFe) space for both as grown and adsorption-modified films. Our results indicate how to precisely engineer in-plane MA that can be controlled by dCo, dFe and is sensitive to the residual gas adsorption.

Deposition of MgB2 Thin Films on Alumina-Buffered Si Substrates by using Hybrid Physical-Chemical Vapor Deposition Method

International Nuclear Information System (INIS)

Lee, T. G.; Park, S. W.; Seong, W. K.; Huh, J. Y.; Jung, S. G.; Kang, W. N.; Lee, B. K.; An, K. S.

2008-01-01

[ MgB 2 ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures 500 - 600 degrees C and under the reactor pressures of 25 - 50 degrees C. There are some interfacial reactions in the as-grown films with impurities of mostly Mg 2 Si, MgAl 2 O 4 , and other phases. The T c 's of MgB 2 films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly Mg 2 Si impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

The effect of Cr substitution on the structural, electronic and magnetic properties of pulsed laser deposited NiFe_2O_4 thin films

International Nuclear Information System (INIS)

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

2017-01-01

We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni_1_−_xCr_xFe_2O_4 (x=0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties. - Highlights: • Thin films of Ni_1_−_xCr_xFe_2O_4 are grown on Si(111) and Si(100) substrates. • Films on Si(111) substrate are better crystalline than those on Si(100). • XRD and FTIR results confirm the single phase growth of the films. • Cationic distribution deviates from inverse spinel structure, as revealed by XPS. • Saturation magnetization is larger on Si(100) but lower than the bulk value.

Magnetic fabrics and fluid flow directions in hydrothermal systems. A case study in the Chaillac Ba-F-Fe deposits (France)

Science.gov (United States)

Sizaret, Stanislas; Chen, Yan; Chauvet, Alain; Marcoux, Eric; Touray, Jean Claude

2003-02-01

This study presents a possible use of anisotropy of magnetic susceptibility (AMS) to describe the mineralizing process in hydrothermal systems. Ba-F-Fe-rich deposits within the Chaillac Basin are on the southern border of the Paris Basin. In these deposits hydrothermal textures and tectonic structures have been described in veins, sinters, and sandstone cemented by hydrothermal goethite. 278 oriented cores from 24 sites have been collected in these formations. In addition, a lateritic duricrust superimposed on the hydrothermal formation has been sampled. Rock magnetic investigations show that the principal magnetic carrier is goethite for the hydrothermal mineralization and for the laterite level. The AMS measurements show distinguishable behaviors in the different mineralogical and geological contexts. The K1 magnetic lineation (maximum axis) is strongly inclined for the vertical veins. For the horizontally mineralized sinters, the magnetic lineation is almost horizontal with an azimuth similar to the sedimentary flow direction. The AMS of goethite-rich sandstone close to the veins shows strongly inclined K1 as they are probably influenced by the vertical veins; however, when the distance from the vein is larger than 1 m, the AMS presents rather horizontal K1 directions, parallel to the sedimentary flow. The laterite has a foliation dominance of AMS with vertically well-grouped K3 axes and scattered K1 and K2 axes. Field structural observations suggest that the ore deposit is mainly controlled by EW extension tectonics associated with NS trending normal faults. Combining the AMS results on the deposit with vein textures and field data a model is proposed in which AMS results are interpreted in terms of hydrothermal fluid flow. This work opens a new investigation field to constrain hydrodynamic models using the AMS method. Textural study combined with efficient AMS fabric measurements should be used for systematic investigation to trace flow direction in fissures

Tuning magnetic properties of magnetoelectric BiFeO 3-NiFe 2O 4 nanostructures

Science.gov (United States)

Crane, S. P.; Bihler, C.; Brandt, M. S.; Goennenwein, S. T. B.; Gajek, M.; Ramesh, R.

2009-02-01

Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.

Tuning magnetic properties of magnetoelectric BiFeO3-NiFe2O4 nanostructures

International Nuclear Information System (INIS)

Crane, S.P.; Bihler, C.; Brandt, M.S.; Goennenwein, S.T.B.; Gajek, M.; Ramesh, R.

2009-01-01

Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2 O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars

Preparation and electric and photoelectric properties of thin deposits of Fe, Co, Ni, Cu, Ag, Au and Pd

International Nuclear Information System (INIS)

Heras, J.M.; Albano, E.V.; Asensio, M.C.; Viscido, L.

1984-01-01

The physics chemical properties of desordered metallic thin films of Fe, Co, Ni, Pd, Ag, Cu and Au are of great interest for its catalitic activity and for its application in radiation absorption of solar cells and micro electronic devices. This work has the purpose of reporting the experimental results obtained by evaporated films of these metals, which present desordered characteristics, small crystal size and high surface-volume rate. (A.C.A.S.) [pt

Effect of Fe-Mn addition on microstructure and magnetic properties of NdFeB magnetic powders

Science.gov (United States)

Kurniawan, C.; Purba, A. S.; Setiadi, E. A.; Simbolon, S.; Warman, A.; Sebayang, P.

2018-03-01

In this paper, the effect of Fe-Mn alloy addition on microstructures and magnetic properties of NdFeB magnetic powders was investigated. Varied Fe-Mn compositions of 1, 5, and 10 wt% were mixed with commercial NdFeB type MQA powders for 15 minutes using shaker mill. The characterizations were performed by powder density, PSA, XRD, SEM, and VSM. The Fe-Mn addition increased the powder density of NdFeB/Fe-Mn powders. On the other side, particle size distribution slightly decreased as the Fe-Mn composition increases. Magnetic properties of NdFeB/Fe-Mn powders changed with the increasing of Fe-Mn content. SEM analysis showed the particle size of NdFeB/Fe-Mn powder was smaller as the Fe-Mn composition increases. It showed that NdFeB/Fe-Mn particles have different size and shape for NdFeB and Fe-Mn particles separately. The optimum magnetic properties of NdFeB/Fe-Mn powder was achieved on the 5 wt% Fe-Mn composition with remanence M r = 49.45 emu/g, coercivity H c = 2.201 kOe, and energy product, BH max = 2.15 MGOe.

Advanced deposition model for thermal activated chemical vapor deposition

Science.gov (United States)

Cai, Dang

Thermal Activated Chemical Vapor Deposition (TACVD) is defined as the formation of a stable solid product on a heated substrate surface from chemical reactions and/or dissociation of gaseous reactants in an activated environment. It has become an essential process for producing solid film, bulk material, coating, fibers, powders and monolithic components. Global market of CVD products has reached multi billions dollars for each year. In the recent years CVD process has been extensively used to manufacture semiconductors and other electronic components such as polysilicon, AlN and GaN. Extensive research effort has been directed to improve deposition quality and throughput. To obtain fast and high quality deposition, operational conditions such as temperature, pressure, fluid velocity and species concentration and geometry conditions such as source-substrate distance need to be well controlled in a CVD system. This thesis will focus on design of CVD processes through understanding the transport and reaction phenomena in the growth reactor. Since the in situ monitor is almost impossible for CVD reactor, many industrial resources have been expended to determine the optimum design by semi-empirical methods and trial-and-error procedures. This approach has allowed the achievement of improvements in the deposition sequence, but begins to show its limitations, as this method cannot always fulfill the more and more stringent specifications of the industry. To resolve this problem, numerical simulation is widely used in studying the growth techniques. The difficulty of numerical simulation of TACVD crystal growth process lies in the simulation of gas phase and surface reactions, especially the latter one, due to the fact that very limited kinetic information is available in the open literature. In this thesis, an advanced deposition model was developed to study the multi-component fluid flow, homogeneous gas phase reactions inside the reactor chamber, heterogeneous surface

LaFePdO3 perovskite automotive catalyst having a self-regenerative function

International Nuclear Information System (INIS)

Tanaka, Hirohisa; Tan, Isao; Uenishi, Mari; Taniguchi, Masashi; Kimura, Mareo; Nishihata, Yasuo; Mizuki, Jun'ichiro

2006-01-01

An automotive gasoline engine is operated close to the stoichiometric air-to-fuel ratio to convert the pollutant emissions simultaneously, accompanying with redox (reduction and oxidation) fluctuations in exhaust-gas composition through adjusting the air-to-fuel ratio. An innovative LaFe 0.95 Pd 0.05 O 3 perovskite catalyst, named 'the intelligent catalyst', has been developed, and which has a new self-regenerative function of the precious metal in the inherent fluctuations of automotive exhaust-gas. The LaFe 0.95 Pd 0.05 O 3 perovskite catalyst, La located at the A-site, was prepared by the alkoxide method. Pd located at the B-site of the perovskite lattice in the oxidative atmosphere, and segregated out to form small metallic particles in the reductive atmosphere. The catalyst retained a predominantly perovskite structure throughout a redox cycle of the exhaust-gas, while the local structure around Pd could be changed in a completely reversible manner. The agglomeration and growth of Pd particles is suppressed, even under the severe environment, as a result of the movement between inside and outside the perovskite lattice. It is revealed that the self-regenerative function of Pd occurs even at 200 deg. C, unexpectedly low temperature, in the LaFe 0.95 Pd 0.05 O 3 catalyst. Since the high catalytic activity is maintained, the great reduction of Pd loading has been achieved. The intelligent catalyst is expected as a new application of the rare earth, and then the technology is expected in the same way in the global standard of the catalyst designing

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.

Copper-vapor-catalyzed chemical vapor deposition of graphene on dielectric substrates

Science.gov (United States)

Yang, Chao; Wu, Tianru; Wang, Haomin; Zhang, Xuefu; Shi, Zhiyuan; Xie, Xiaoming

2017-07-01

Direct synthesis of high-quality graphene on dielectric substrates is important for its application in electronics. In this work, we report the process of copper-vapor-catalyzed chemical vapor deposition of high-quality and large graphene domains on various dielectric substrates. The copper vapor plays a vital role on the growth of transfer-free graphene. Both single-crystal domains that are much larger than previous reports and high-coverage graphene films can be obtained by adjusting the growth duration. The quality of the obtained graphene was verified to be comparable with that of graphene grown on Cu foil. The progress reported in this work will aid the development of the application of transfer-free graphene in the future.

A study of coFeB magnetic yoke based on planar electromagnet

Science.gov (United States)

Qin, L.; Li, Q.; Yuan, Yong J.

2017-07-01

This paper studies the fabrication of a novel planar electromagnet consisting of a planar copper coil and a magnetic yoke. CoFeB was used as the magnetic yoke material instead of the traditional permanent magnets. The planar electromagnet was fabricated and optimized to maximize the electromagnetic force, especially with varying CoFeB thickness. The micro-planar electromagnet was fabricated successfully by the traditional micro-electro-mechanical-system (MEMS) techniques and XRD, VSM were used to characterize the performance of the electromagnet. The planar electromagnet exhibits superior perpendicular magnetic anisotropy (PMA) and 0.006 emu of MS was achieved following 2 min deposition of CoFeB thin film. By integrating with other micro apparatuses, it is anticipated that the planar electromagnet will have potential applications in areas such as biosensors, biological medicine, drug delivery, chemical analysis and environmental monitoring.

Enthalpy and high temperature relaxation kinetics of stable vapor-deposited glasses of toluene

International Nuclear Information System (INIS)

Bhattacharya, Deepanjan; Sadtchenko, Vlad

2014-01-01

Stable non-crystalline toluene films of micrometer and nanometer thicknesses were grown by vapor deposition at distinct rates and probed by fast scanning calorimetry. Fast scanning calorimetry is shown to be extremely sensitive to the structure of the vapor-deposited phase and was used to characterize simultaneously its kinetic stability and its thermodynamic properties. According to our analysis, transformation of vapor-deposited samples of toluene during heating with rates in excess 10 5 K s −1 follows the zero-order kinetics. The transformation rate correlates strongly with the initial enthalpy of the sample, which increases with the deposition rate according to sub-linear law. Analysis of the transformation kinetics of vapor-deposited toluene films of various thicknesses reveal a sudden increase in the transformation rate for films thinner than 250 nm. The change in kinetics seems to correlate with the surface roughness scale of the substrate. The implications of these findings for the formation mechanism and structure of vapor-deposited stable glasses are discussed

Electric field modulation of magnetic anisotropy and microwave absorption properties in Fe50Ni50/Teflon composite films

Directory of Open Access Journals (Sweden)

Zhenjun Xia

2016-05-01

Full Text Available Fe50Ni50 nanoparticle films with the size about 6 nm were deposited by a high energetic cluster deposition source. An electric field of about 0 - 40 kV was applied on the sample platform when the films were prepared. The field assisted deposition technique can dramatically induce in-plane magnetic anisotropy. To probe the microwave absorption properties, the Fe50Ni50 nanoparticles were deliberately deposited on the dielectric Teflon sheet. Then the laminated Fe50Ni50/Teflon composites were used to do reflection loss scan. The results prove that the application of electric field is an effective avenue to improve the GHz microwave absorption performance of our magnetic nanoparticles films expressed by the movement of reflection loss peak to high GHz region for the composites.

Magnetic and microstructural properties of thin NdFeB based films and nanostructures

Energy Technology Data Exchange (ETDEWEB)

Bommer, Lars; Goll, Dagmar [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

2010-07-01

The magnetic and microstructural properties of NdFeB and NdFeB/Fe thin films and nanostructures are presented. Samples with Cr buffer and protection layer (minimum thickness: d=50 nm) have been produced by ion beam sputtering at elevated temperatures (T{sub s}=700 C) using Al{sub 2}O{sub 3} and MgO(001) single crystal substrates. Films deposited on Al{sub 2}O{sub 3} substrates show c-axis growth in out-of-plane direction down to thicknesses of the NdFeB film of d=10 nm with coercivities up to {mu}{sub 0}H{sub c}=1 T. The texture of films deposited on MgO(001) substrates is less pronounced and films below d=20 nm show no hard magnetic behavior. For comparison, films were deposited at room temperature on Al{sub 2}O{sub 3} and MgO(001) followed by post-annealing in Ar atmosphere (T{sub pa}=525-650 C) leading to coercivities as high as {mu}{sub 0}H{sub c}=1.2 T but with isotropic behavior. By TEM images the grain structure of the NdFeB samples is studied. Bilayers of NdFeB (d=50 nm) and Fe (d=0-20 nm) show fully exchange coupled behavior. From the temperature dependence of the coercivity the microstructural parameters of all samples have been determined. Furthermore NdFeB periodical patterns were produced by means of electron beam lithography with dot sizes of 1000 nm and 500 nm, respectively.

Effects of an external magnetic field in pulsed laser deposition

Science.gov (United States)

García, T.; de Posada, E.; Villagrán, M.; Ll, J. L. Sánchez; Bartolo-Pérez, P.; Peña, J. L.

2008-12-01

Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe 12O 19 target with and without the presence of a nonhomogeneous magnetic field of μ0H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

Effects of an external magnetic field in pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Garcia, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, C.P. 09790, Mexico DF (Mexico)], E-mail: tupacgarcia@yahoo.com; Posada, E. de [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico); Villagran, M. [CCADET, Universidad Nacional Autonoma de Mexico (UNAM), A.P. 70-186, C.P. 04510, Mexico DF (Mexico); Ll, J.L. Sanchez [Laboratorio de Magnetismo, Facultad de Fisica-IMRE, Universidad de La Habana, La Habana 10400 (Cuba); Bartolo-Perez, P.; Pena, J.L. [CINVESTAV-IPN Unidad Merida, Applied Physics Department, A.P. 73, Cordemex, C.P. 97130 Merida, Yuc. (Mexico)

2008-12-30

Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe{sub 12}O{sub 19} target with and without the presence of a nonhomogeneous magnetic field of {mu}{sub 0}H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.

Synthesis and magnetic properties of the thin film exchange spring system of MnBi/FeCo

Science.gov (United States)

Sabet, S.; Hildebrandt, E.; Alff, L.

2017-10-01

Manganese bismuth thin films with a nominal thickness of ∼40 nm were grown at room temperature onto quartz glass substrate in a DC magnetron sputtering unit. In contrast to the usual multilayer approach, the MnBi films were deposited using a single sputtering target with a stoichiometry of Mn55Bi45 (at. %). A subsequent in-situ annealing step was performed in vacuum in order to form the ferromagnetic LTP of MnBi. X-ray diffraction confirmed the formation of a textured LTP MnBi hard phase after annealing at 330 °C. This film shows a maximum saturation magnetization of 530 emu/cm3, high out-of-plane coercivity of 15 kOe induced by unreacted bismuth. The exchange coupling effect was investigated by deposition of a second layer of FeCo with 1 nm and 2 nm thickness onto the LTP MnBi films. The MnBi/FeCo double layer showed as expected higher saturation magnetization with increasing thickness of the FeCo layer while the coercive field remained constant. The fabrication of the MnBi/FeCo double layer for an exchange spring magnet was facilitated by deposition from a single stoichiometric target.

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 and magnetotransport properties of Fe nanoparticles embedded in Ag matrix

Energy Technology Data Exchange (ETDEWEB)

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

2005-04-15

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

Magnetic and magnetotransport properties of Fe nanoparticles embedded in Ag matrix

International Nuclear Information System (INIS)

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

2005-01-01

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

Growth and magnetic study of sputtered Fe/Al multilayers

International Nuclear Information System (INIS)

Cherif, S.M.; Bouziane, K.; Roussigne, Y.; Al-Busaidy, M.

2007-01-01

Brillouin light scattering (BLS) and vibrating sample magnetometry (VSM) were used to study the effect of interfacial intermixing and microstructure on the magnetic properties of DC magnetron sputtered Fe/Al multilayers (MLs) on Si(1 0 0) substrate. Three samples with nominal composition [Al (4 nm)/Fe (3.7 nm)] x18 and deposited under different negative DC bias voltages (V b = -50, -200 and -400 V) have been investigated. The X-ray diffraction results indicate that the FeAl MLs have a poor crystallinity with no evidence of the absence of B2 phase. The grazing X-ray reflectivity results suggest that the interfacial roughness and intermixing were gradually reduced from 0.7 to 0.5 nm (±0.05 nm) by increasing V b from -50 to -400 V. The magnetization measurements demonstrate the presence of in-plane uniaxial anisotropy and magnetically dead interfacial layers. The BLS results reveal spin-wave surface modes whose frequencies also depend on the applied V b . The same trend upon V b was observed for the perpendicular and in-plane anisotropies

Growth and magnetic study of sputtered Fe/Al multilayers

Energy Technology Data Exchange (ETDEWEB)

Cherif, S.M. [LPMTM (CNRS-UPR 9001), Universite Paris 13, 99 Av. J.B. Clement, 93430 Villetaneuse (France); Bouziane, K. [LPMTM (CNRS-UPR 9001), Universite Paris 13, 99 Av. J.B. Clement, 93430 Villetaneuse (France) and Department of Physics, College of Science, Sultan Qaboos University, P.O. Box 36, Al-Khodh 123 (Oman)]. E-mail: bouzi@squ.edu.om; Roussigne, Y. [LPMTM (CNRS-UPR 9001), Universite Paris 13, 99 Av. J.B. Clement, 93430 Villetaneuse (France); Al-Busaidy, M. [Department of Physics, College of Science, Sultan Qaboos University, P.O. Box 36, Al-Khodh 123 (Oman)

2007-03-15

Brillouin light scattering (BLS) and vibrating sample magnetometry (VSM) were used to study the effect of interfacial intermixing and microstructure on the magnetic properties of DC magnetron sputtered Fe/Al multilayers (MLs) on Si(1 0 0) substrate. Three samples with nominal composition [Al (4 nm)/Fe (3.7 nm)]{sub x18} and deposited under different negative DC bias voltages (V {sub b} = -50, -200 and -400 V) have been investigated. The X-ray diffraction results indicate that the FeAl MLs have a poor crystallinity with no evidence of the absence of B2 phase. The grazing X-ray reflectivity results suggest that the interfacial roughness and intermixing were gradually reduced from 0.7 to 0.5 nm ({+-}0.05 nm) by increasing V {sub b} from -50 to -400 V. The magnetization measurements demonstrate the presence of in-plane uniaxial anisotropy and magnetically dead interfacial layers. The BLS results reveal spin-wave surface modes whose frequencies also depend on the applied V{sub b}. The same trend upon V {sub b} was observed for the perpendicular and in-plane anisotropies.

Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials.

Science.gov (United States)

Yang, Minghong; Dai, Jixiang; Zhou, Ciming; Jiang, Desheng

2009-11-09

Different from usually-used bulk magnetostrictive materials, magnetostrictive TbDyFe thin films were firstly proposed as sensing materials for fiber-optic magnetic field sensing characterization. By magnetron sputtering process, TbDyFe thin films were deposited on etched side circle of a fiber Bragg Grating (FBG) as sensing element. There exists more than 45pm change of FBG wavelength when magnet field increase up to 50 mT. The response to magnetic field is reversible, and could be applicable for magnetic and current sensing.

Ultra-fine structures of Pd-Ag-HAp nanoparticle deposition on protruded TiO2 barrier layer for dental implant

Science.gov (United States)

Jang, Jae-Myung; Kim, Seung-Dai; Park, Tae-Eon; Choe, Han-Cheol

2018-02-01

The biocompatibility structure of an implant surface is of great importance to the formation of new bone tissue around the dental implant and also has a significant chemical reaction in the osseointegration process. Thus, ultra-fine Pd-Ag-HAp nanoparticles have been electrodeposited on protruded TiO2 barrier layer in mixed electrolyte solutions. Unusual protrusions patterns, which are assigned to Pd-Ag-HAp nanoparticles, can be clearly differentiated from a TiO2 nanotube oxide layer formed by an anodizing process. In the chemical bonding state, the surface characteristics of Pd/Ag/HAp compounds have been investigated by FE-SEM, EDS mapping analysis, and XPS analysis. The mapping dots of the elements including Ti, Ca, Pd, Ag, and P showed a homogeneous distribution throughout the entire surface when deposited onto the protruded TiO2 barrier layer. The XPS spectra of Ti-2p, O-1S, Pd-3d, and Ag-3d have been investigated, with the major XPS peak indicating Pd-3d. The Ag-3d level was clearly observed with further scanning of the Ca-2p region. Based on the results of the chemical states, the structural properties of the protrusion patterns were also examined after being deposited onto the barrier oxide film, resulting in the representative protrusion patterns being mainly composed of Pd-Ag-HAp compounds. The results of the soaking evaluation showed that the protrusion patterns and the protruded TiO2 barrier layer were all effective in regards to biocompatibility.

Novel Fe-Pd/SiO2 catalytic materials for degradation of chlorinated organic compounds in water

Science.gov (United States)

Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH4

Magnetic binary nanofillers

International Nuclear Information System (INIS)

Morales Mendoza, N.; Goyanes, S.; Chiliotte, C.; Bekeris, V.; Rubiolo, G.; Candal, R.

2012-01-01

Magnetic binary nanofillers containing multiwall carbon nanotubes (MWCNT) and hercynite were synthesized by Chemical Vapor Deposition (CVD) on Fe/AlOOH prepared by the sol-gel method. The catalyst precursor was fired at 450 °C, ground and sifted through different meshes. Two powders were obtained with different particle sizes: sample A (50-75 μm) and sample B (smaller than 50 μm). These powders are composed of iron oxide particles widely dispersed in the non-crystalline matrix of aluminum oxide and they are not ferromagnetic. After reduction process the powders are composed of α-Fe nanoparticles inside hercynite matrix. These nanofillers are composed of hercynite containing α-Fe nanoparticles and MWCNT. The binary magnetic nanofillers were slightly ferromagnetic. The saturation magnetization of the nanofillers depended on the powder particle size. The nanofiller obtained from powder particles in the range 50-75 μm showed a saturation magnetization 36% higher than the one formed from powder particles smaller than 50 μm. The phenomenon is explained in terms of changes in the magnetic environment of the particles as consequence of the presence of MWCNT.

Magnetic binary nanofillers

Energy Technology Data Exchange (ETDEWEB)

Morales Mendoza, N. [INQUIMAE, CONICET-UBA, Ciudad Universitaria, Pab2, (C1428EHA) Bs As (Argentina); LPyMC, Dep. De Fisica, FCEN-UBA and IFIBA -CONICET, Ciudad Universitaria, Cap. Fed. (Argentina); Goyanes, S. [LPyMC, Dep. De Fisica, FCEN-UBA and IFIBA -CONICET, Ciudad Universitaria, Cap. Fed. (Argentina); Chiliotte, C.; Bekeris, V. [LBT, Dep. De Fisica, FCEN-UBA. Ciudad Universitaria, Pab1, C1428EGA CABA (Argentina); Rubiolo, G. [LPyMC, Dep. De Fisica, FCEN-UBA and IFIBA -CONICET, Ciudad Universitaria, Cap. Fed. (Argentina); Unidad de Actividad Materiales, CNEA, Av Gral. Paz 1499, San Martin (1650), Prov. de Bs As (Argentina); Candal, R., E-mail: candal@qi.fcen.uba.ar [INQUIMAE, CONICET-UBA, Ciudad Universitaria, Pab2, (C1428EHA) Bs As (Argentina); Escuela de Ciencia y Tecnologia, 3iA, Universidad de Gral. San Martin, San Martin, Prov. Bs As (Argentina)

2012-08-15

Magnetic binary nanofillers containing multiwall carbon nanotubes (MWCNT) and hercynite were synthesized by Chemical Vapor Deposition (CVD) on Fe/AlOOH prepared by the sol-gel method. The catalyst precursor was fired at 450 Degree-Sign C, ground and sifted through different meshes. Two powders were obtained with different particle sizes: sample A (50-75 {mu}m) and sample B (smaller than 50 {mu}m). These powders are composed of iron oxide particles widely dispersed in the non-crystalline matrix of aluminum oxide and they are not ferromagnetic. After reduction process the powders are composed of {alpha}-Fe nanoparticles inside hercynite matrix. These nanofillers are composed of hercynite containing {alpha}-Fe nanoparticles and MWCNT. The binary magnetic nanofillers were slightly ferromagnetic. The saturation magnetization of the nanofillers depended on the powder particle size. The nanofiller obtained from powder particles in the range 50-75 {mu}m showed a saturation magnetization 36% higher than the one formed from powder particles smaller than 50 {mu}m. The phenomenon is explained in terms of changes in the magnetic environment of the particles as consequence of the presence of MWCNT.

Spin crossover behaviour in Hofmann-like coordination polymer Fe(py)2[Pd(CN)4] with 57Fe Mössbauer spectra

Science.gov (United States)

Kitazawa, Takafumi; Kishida, Takanori; Kawasaki, Takeshi; Takahashi, Masashi

2017-11-01

We have prepared the 2D spin crossover complexes Fe(L)2Pd(CN)4 (L = py : 1a; py-D5 : 1b and py-15N : 1c). 1a has been characterised by 57Fe Mossbauer spectroscopic measurements, single crystal X-ray determination and SQUID measurements. The Mössbauer spectra for 1a indicate that the iron(II) spin states are in high spin states at 298 K and are in low spin states at 77 K. The crystal structures of 1a at 298 K and 90 K also show the high spin state and the low spin state respectively, associated with the Fe(II)-N distances. The spin transition temperature range of 1a is higher than that of Fe(py)2Ni(CN)4 since Pd(II) ions are larger and heavier than Ni(II) ions. SQUID data indicate isotope effects among 1a, 1b and 1c are observed in very small shifts of the transition temperatures probably due to larger and heavier Pd(II) ions. The delicate shifts would be associated with subtle balances between different vibrations around Fe(II) atoms and electronic factors.

Surface morphology of scale on FeCrAl (Pd, Pt, Y) alloys

International Nuclear Information System (INIS)

Amano, T.; Takezawa, Y.; Shiino, A.; Shishido, T.

2008-01-01

The high temperature oxidation behavior of Fe-20Cr-4Al, floating zone refined (FZ) Fe-20Cr-4Al, Fe-20Cr-4Al-0.5Pd, Fe-20Cr-4Al-0.5Pt and Fe-20Cr-4Al-(0.01, 0.02, 0.05, 0.1, 0.2, 0.5)Y alloys was studied in oxygen for 0.6-18 ks at 1273-1673 K by mass gain measurements, X-ray diffraction and scanning electron microscopy. The mass gains of FeCrAl, FZ FeCrAl, FeCrAlPd and FeCrAlPt alloys showed almost the same values. Those of FeCrAl-(0.01, 0.02, 0.05, 0.1, 0.2, 0.5)Y alloys decreased with increasing yttrium of up to 0.1% followed by an increase with the yttrium content after oxidation for 18 ks at 1473 K. Needle-like oxide particles were partially observed on FeCrAl alloy after oxidation for 7.2 ks at 1273 K. These oxide particles decreased in size with increasing oxidation time of more than 7.2 ks at 1473 K, and then disappeared after oxidation for 7.2 ks at 1573 K. It is suggested that a new oxide develops at the oxygen/scale interface. The scale surface of FeCrAl alloy showed a wavy morphology after oxidation for 7.2 ks at 1273 K which then changed to planar morphology after an oxidation time of more than 7.2 ks at 1573 K. On the other hand, the scale surfaces of other alloys were planar after all oxidation conditions in this study. The scale surfaces of FeCrAl, FZ FeCrAl, FeCrAlPd and FeCrAlPt alloys were rough, however, those of FeCrAl-(0.1, 0.2, 0.5)Y alloys were smooth. The oxide scales formed on FeCrAl-(0.1, 0.2, 0.5)Y alloys were found to be α-Al 2 O 3 with small amounts of Y 3 Al 5 O 12 , and those of the other alloys were only α-Al 2 O 3

Photoelectron diffraction of magnetic ultrathin films: Fe/Cu(001)

Energy Technology Data Exchange (ETDEWEB)

Tobin, J.G. (Lawrence Livermore National Lab., CA (USA)); Wagner, M.K. (Wisconsin Univ., Madison, WI (USA). Dept. of Chemistry); Guo, X.Q.; Tong, S.Y. (Wisconsin Univ., Milwaukee, WI (USA). Dept. of Physics)

1991-01-03

The preliminary results of an ongoing investigation of Fe/Cu(001) are presented here. Energy dependent photoelectron diffraction, including the spin-dependent variant using the multiplet split Fe3s state, is being used to investigate the nanoscale structures formed by near-monolayer deposits of Fe onto Cu(001). Core-level photoemission from the Fe3p and Fe3s states has been generated using synchrotron radiation as the tunable excitation source. Tentatively, a comparison of the experimental Fe3p cross section measurements with multiple scattering calculations indicates that the Fe is in a fourfold hollow site with a spacing of 3.6{Angstrom} between it and the atom directly beneath it, in the third layer. This is consistent with an FCC structure. The possibility of utilizing spin-dependent photoelectron diffraction to investigate magnetic ultrathin films will be demonstrated, using our preliminary spectra of the multiplet-split Fe3s os near-monolayer Fe/Cu(001). 18 refs., 10 figs.

Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

Science.gov (United States)

Kunoh, Tatsuki; Hashimoto, Hideki; McFarlane, Ian R.; Hayashi, Naoaki; Suzuki, Tomoko; Taketa, Eisuke; Tamura, Katsunori; Takano, Mikio; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

2016-01-01

Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths. PMID:27271677

Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths

Directory of Open Access Journals (Sweden)

Tatsuki Kunoh

2016-06-01

Full Text Available Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II to Fe(III and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II concentrations, Fe(III precipitates visibly formed immediately after addition of Fe(II to the medium, suggesting prompt abiotic oxidation of Fe(II to Fe(III. Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter, while those in the Fe(III medium were composed of large, aggregated particles (≥3 µm diameter with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved of Fe encrustation of the Leptothrix sheaths.

Molecular Models for DSMC Simulations of Metal Vapor Deposition

OpenAIRE

Venkattraman, A; Alexeenko, Alina A

2010-01-01

The direct simulation Monte Carlo (DSMC) method is applied here to model the electron‐beam (e‐beam) physical vapor deposition of copper thin films. A suitable molecular model for copper‐copper interactions have been determined based on comparisons with experiments for a 2D slit source. The model for atomic copper vapor is then used in axi‐symmetric DSMC simulations for analysis of a typical e‐beam metal deposition system with a cup crucible. The dimensional and non‐dimensional mass fluxes obt...

Hydrogen-Induced Buckling of Pd Films Deposited on Various Substrates

KAUST Repository

Vlček, Marián

2015-07-01

A Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of the substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.

Hydrogen-Induced Buckling of Pd Films Deposited on Various Substrates

KAUST Repository

Vlček, Mariá n; Luká č, František; Vlach, Martin; Prochá zka, Ivan; Wagner, Stefan; Uchida, Helmut; Pundt, Astrid; Gemma, Ryota; Čí žek, Jakub

2015-01-01

A Pd-H system is a model system suitable for studying interactions of hydrogen with metals. In the present work, we studied hydrogen-induced buckling of thin Pd films deposited on various substrates with different bonding strengths (sapphire, glimmer) and also the effect of deposition temperature. Lattice expansion and phase transitions were investigated by X-ray diffraction of synchrotron radiation. The influence of the substrate and microstructure of the film on the buckling process and phase transformation to palladium hydride are discussed.

Low-pressure chemical vapor deposition as a tool for deposition of thin film battery materials

NARCIS (Netherlands)

Oudenhoven, J.F.M.; Dongen, van T.; Niessen, R.A.H.; Croon, de M.H.J.M.; Notten, P.H.L.

2009-01-01

Low Pressure Chemical Vapor Deposition was utilized for the deposition of LiCoO2 cathode materials for all-solid-state thin-film micro-batteries. To obtain insight in the deposition process, the most important process parameters were optimized for the deposition of crystalline electrode films on

Quasicubic α-Fe{sub 2}O{sub 3} nanoparticles embedded in TiO{sub 2} thin films grown by atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Tamm, Aile [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Seinberg, Liis [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Kozlova, Jekaterina [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Link, Joosep [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Pikma, Piret [University of Tartu, Institute of Chemistry, Ravila 14A, 50411 Tartu (Estonia); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Kukli, Kaupo [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland)

2016-08-01

Monodispersed quasicubic α-Fe{sub 2}O{sub 3} nanoparticles were synthesized from ferric nitrite (Fe(NO{sub 3}){sub 3}), N,N-dimethyl formamide and poly(N-vinyl-2-pyrrolidone). Layers of nanoparticles were attached to HF-etched Si substrates by dip coating and subsequently embedded in thin titanium oxide films grown by atomic layer deposition from TiCl{sub 4} and H{sub 2}O. The deposition of TiO{sub 2} onto Fe{sub 2}O{sub 3} nanoparticles covered the nanoparticles uniformly and anatase phase of TiO{sub 2} was observed in Si/Fe{sub 2}O{sub 3}/TiO{sub 2} nanostructures. In Si/Fe{sub 2}O{sub 3}/TiO{sub 2} nanostructure magnetic domains, observable by magnetic force microscopy, were formed and these nanostructures implied ferromagnetic-like behavior at room temperature with the saturative magnetization and coercivity of 10 kA/m. - Highlights: • Cubic-shaped iron oxide crystallites were supported by thin titanium oxide films. • The process chemistry applied allowed formation of heterogeneous composite. • Atomic layer deposition of titanium oxide on nanocubes was uniform and conformal. • The nanostructures formed can be regarded as magnetically susceptible materials.

Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers

International Nuclear Information System (INIS)

Miko, Annamaria; Kuzmann, Erno; Lakatos-Varsanyi, Magda; Kakay, Attila; Nagy, Ferenc; Varga, Lajos Karoly

2005-01-01

57 Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and 57 Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t on = 2 ms), with short relaxation time (t off = 9 ms) and low current density (I p = 0.05 Acm -2 ) or at short deposition time (t on = 1 ms) with long relaxation time (t off = 250 ms) and high current density (I p = 1.0 Acm -2 ). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.

Kerr microscopy study of exchange-coupled FePt/Fe exchange spring magnets

Energy Technology Data Exchange (ETDEWEB)

Hussain, Zaineb; Kumar, Dileep [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Reddy, V. Raghavendra, E-mail: varimalla@yahoo.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Gupta, Ajay [Amity Center for Spintronic Materials, Amity University, Noida 201303 (India)

2017-05-15

Magnetization reversal and magnetic microstructure of top soft magnetic layer (Fe) in exchange spring coupled L1{sub 0} FePt/Fe is studied using high resolution Kerr microscopy. With remnant state of the hard magnetic layer (L1{sub 0} FePt) as initial condition, magnetization loops along with magnetic domains are recorded for the top soft magnetic layer (Fe) using Kerr microscopy. Considerable shifting of Fe layer hysteresis loop from center which is similar to exchange bias phenomena is observed. It is also observed that one can tune the magnitude of hysteresis shift by reaching the remanent state from different saturating fields (H{sub SAT}) and also by varying the angle between measuring field and H{sub SAT}. The hysteresis loops and magnetic domains of top soft Fe layer demonstrate unambiguously that soft magnetic layer at remanent state in such exchange coupled system is having unidirectional anisotropy. An analogy is drawn and the observations are explained in terms of established model of exchange bias phenomena framed for field-cooled ferromagnetic - antiferromagnetic bilayer systems. - Highlights: • Kerr microscopy of top soft magnetic Fe layer in exchange spring coupled L1{sub 0} FePt (30 nm)/Fe (22 nm) is reported. • Considerable shifting of Fe layer hysteresis loop from center which is similar to exchange bias phenomena is observed. • Tuneable nature of magnitude of hysteresis shift is shown. • It is unambiguously shown that the top soft Fe magnetic layer at remanent state is having unidirectional anisotropy.

Vapor diffusion synthesis of rugby-shaped CoFe{sub 2}O{sub 4}/graphene composites as absorbing materials

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shenli [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Jiao, Qingze [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); School of Chemical Engineering and Materials Science, Beijing Institute of Technology, Zhuhai, Zhuhai 519085 (China); Hu, Ju; Li, Jingjing [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Zhao, Yun, E-mail: zhaoyun@bit.edu.cn [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Li, Hansheng; Wu, Qin [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China)

2015-05-05

Graphical abstract: CoFe{sub 2}O{sub 4} rugbies/graphene composites were prepared using a vapor diffusion method followed by calcination. As-synthesized rugby-like CoFe{sub 2}O{sub 4} particles were distributed on the graphene sheet. PVP played a key role for the formation of rugby-shaped morphology of CoFe{sub 2}O{sub 4} particles. A minimum reflection loss of −39.0 dB was observed at 10.9 GHz for the CoFe{sub 2}O{sub 4} rugbies/graphene composites with a thickness of 2 mm, and the effective absorption bandwidth was 4.7 GHz. The CoFe{sub 2}O{sub 4} rugbies/graphene composites exhibited better microwave absorbing performance than that of the CoFe{sub 2}O{sub 4} nanoparticles/graphene composites prepared without PVP. - Highlights: • CoFe{sub 2}O{sub 4} rugbies/graphene hybrids were synthesized using a vapor diffusion method. • PVP played a key role for the formation of CoFe{sub 2}O{sub 4} rugbies. • CoFe{sub 2}O{sub 4} rugbies/graphene composites showed excellent microwave absorbing property. - Abstract: Rugby-shaped CoFe{sub 2}O{sub 4}/graphene composites were synthesized using a vapor diffusion method in combination with calcination. The morphologies and structures of the products were characterized by field emission scanning electron microscopy, X-ray diffractometer, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. Results show that rugby-shaped CoFe{sub 2}O{sub 4} particles are distributed on graphene sheets. A minimum reflection loss (RL) of −39.0 dB is observed at 10.9 GHz for the sample with a thickness of 2.0 mm, and the effective absorption frequency (RL < −10 dB) ranges from 9.6 to 14.3 GHz, indicating the excellent microwave absorption performance of the products. The absorbing performance of the CoFe{sub 2}O{sub 4} rugbies/graphene composites is better than that of the CoFe

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.

Effect of magnetic soft phase on the magnetic properties of bulk anisotropic Nd2Fe14B/α-Fe nanocomposite permanent magnets

Science.gov (United States)

Li, Yuqing; Yue, Ming; Zhao, Guoping; Zhang, Hongguo

2018-01-01

The effects of soft phase with different particle sizes and distributions on the Nd2Fe14B/α-Fe nanocomposite magnets have been studied by the micro-magnetism simulation. The calculated results show that smaller and/or scattered distribution of soft phase can benefit to the coercivity (H ci) of the nanocomposite magnets. The magnetization moment evolution during magnetic reversal is systematically analyzed. On the other hand, magnetic properties of anisotropic Nd-Fe-B/α-Fe nanocomposite magnets prepared by hot pressing and hot deformation methods also provide evidences for the calculated results.

Magnetism of CrO overlayers on Fe(001)bcc surface: first principles calculations

Science.gov (United States)

Félix-Medina, Raúl Enrique; Leyva-Lucero, Manuel Andrés; Meza-Aguilar, Salvador; Demangeat, Claude

2018-04-01

Riva et al. [Surf. Sci. 621, 55 (2014)] as well as Calloni et al. [J. Phys.: Condens. Matter 26, 445001 (2014)] have studied the oxydation of Cr films deposited on Fe(001)bcc through low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy. In the present work we perform a density functional approach within Quantum Expresso code in order to study structural and magnetic properties of CrO overlayers on Fe(001)bcc. The calculations are performed using DFT+U. The investigated systems include O/Cr/Fe(001)bcc, Cr/O/Fe(001)bcc, Cr0.25O0.75/Fe(001)bcc, as well as the O coverage Ox/Cr/Fe(001)bcc (x = 0.25; 0.50). We have found that the ordered CrO overlayer presents an antiferromagnetic coupling between Cr and Fe atoms. The O atoms are located closer to the Fe atoms of the surface than the Cr atoms. The ground state of the systems O/Cr/Fe(001)bcc and Cr/O/Fe(001)bcc corresponds to the O/Cr/Fe(001)bcc system with a magnetic coupling c(2 × 2). The effect of the O monolayer on Cr/Fe(001)bcc changes the ground state from p(1 × 1) ↓ to c(2 × 2) and produces an enhancement of the magnetic moments. The Ox overlayer on Cr/Fe(001)bcc produces an enhancement of the Cr magnetic moments.

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.

Influence of face-centered-cubic texturing of Co2Fe6B2 pinned layer on tunneling magnetoresistance ratio decrease in Co2Fe6B2/MgO-based p-MTJ spin valves stacked with a [Co/Pd](n)-SyAF layer.

Science.gov (United States)

Takemura, Yasutaka; Lee, Du-Yeong; Lee, Seung-Eun; Chae, Kyo-Suk; Shim, Tae-Hun; Lian, Guoda; Kim, Moon; Park, Jea-Gun

2015-05-15

The TMR ratio of Co2Fe6B2/MgO-based p-MTJ spin valves stacked with a [Co/Pd]n-SyAF layer decreased rapidly when the ex situ magnetic annealing temperature (Tex) was increased from 275 to 325 °C, and this decrease was associated with degradation of the Co2Fe6B2 pinned layer rather than the Co2Fe6B2 free layer. At a Tex above 325 °C the amorphous Co2Fe6B2 pinned layer was transformed into a face-centered-cubic (fcc) crystalline layer textured from [Co/Pd]n-SyAF, abruptly reducing the Δ1 coherence tunneling of perpendicular-spin-torque electrons between the (100) MgO tunneling barrier and the fcc Co2Fe6B2 pinned layer.

Optimization of the Pd-Fe-Mo Catalysts for Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells

International Nuclear Information System (INIS)

Lee, Yeayeon; Jang, Jeongseok; Lee, Jin Goo; Jeon, Ok Sung; Kim, Hyeong Su; Hwang, Ho Jung; Shul, Yong Gun

2016-01-01

Highlights: • Pd-Mo-Fe catalysts show high catalytic activity and stability for oxygen-reduction reactions in acid media. • The optimum compositions were 7.5:1.5:1.0 for Pd-Fe-Mo, and the optimum temperatures were 500 °C. • The Pd-Fe-Mo catalysts were successfully applied to the PEMFC cathode, showing ∼500 mA cm −1 at 0.6 V. • The lattice constant was strongly related to the activity and stability of the catalysts for oxygen-reduction reactions. - Abstract: Highly active and durable non-platinum catalysts for oxygen-reduction reaction (ORR) have been developed for energy conversion devices such as proton-exchange membrane fuel cells (PEMFCs). In this study, Pd-Fe-Mo catalyst is reported as a non-platinum catalyst for ORR. The atomic ratio and annealing temperatures are controlled on the catalysts to understand interplay between their physical and chemical properties and electrochemical activities. The Pd-Fe-Mo catalyst optimized with 7.5:1.5:1.0 of the atomic ratio and 500 °C of the annealing temperature shows 32.18 mA mg −1 PGM (PGM: platinum group metal) of the kinetic current density at 0.9 V for ORR, which is comparable to that of commercial Pt/C catalyst. The current density is degraded to 6.20 mA mg −1 PGM after 3000 cycling of cyclic voltammetry, but it is greatly enhanced value compared to other non-platinum catalysts. In actual application to PEMFCs, the 20% Pd-Fe-Mo catalyst supported on carbons exhibits a high performance of 506 mA cm −2 at 0.6 V. The results suggest that the Pd-Fe-Mo catalyst can be a good candidate for non-platinum ORR catalysts.

Deposition of Fe-Ni nanoparticles on Al2O3 for dechlorination of chloroform and trichloroethylene

International Nuclear Information System (INIS)

Hsieh, S.-H.; Horng, J.-J.

2006-01-01

This research proposes an efficient method for depositing Fe-Ni nanoparticles on Al 2 O 3 microparticles to decompose containments in ground water, such as chloroform and trichloroethylene. The Fe-Ni nanoparticles can be deposited onto the surface of Al 2 O 3 microparticles by electroless plating technique. The reasons why the Fe-Ni nanoparticles would be deposited on the surface of Al 2 O 3 microparticles is to avoid the agglomeration of Fe-Ni nanoparticles due to their surface effect and magnetic property. The results show that the sizes of Fe-Ni particles on Al 2 O 3 particles are between several and several hundreds of nanometers, the contents of Fe and Ni in Fe-Ni nanoparticles can be adjusted from 8 to 60 at.% for Fe and 40 to 92 at.% for Ni, the specific surface area of Fe-Ni nanoparticles can reach to 117 m 2 /g, and the reaction mechanism of dechlorination of chloroform of 2 mg/L by Fe-Ni/Al 2 O 3 particles of 5 g/L appears to be pseudo first order with a half life of 0.7 h and the half life is 0.25 h for the dechlorination of trichloroethylene of 2 mg/L

Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers

Energy Technology Data Exchange (ETDEWEB)

Puttaswamy, Manjunath; Vehkamäki, Marko [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Kukli, Kaupo, E-mail: kaupo.kukli@helsinki.fi [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); University of Tartu, Institute of Physics, W. Ostwald 1, EE-50411 Tartu (Estonia); Dimri, Mukesh Chandra [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Kemell, Marianna; Hatanpää, Timo; Heikkilä, Mikko J. [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki (Finland); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Ritala, Mikko; Leskelä, Markku [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland)

2016-07-29

Bismuth iron oxide films with varying contributions from Fe{sub 2}O{sub 3} or Bi{sub 2}O{sub 3} were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} layers. Films grown at 140 °C to the thickness of 200–220 nm were amorphous, but crystallized upon post-deposition annealing at 500 °C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5 μC/cm{sup 2} and magnetic coercivity varying from a few up to 8000 A/m. - Highlights: • Bismuth iron oxide thin films were grown by atomic layer deposition at 140 °C. • The major phase formed in the films upon annealing at 500 °C was BiFeO{sub 3}. • BiFeO{sub 3} films and films containing excess Bi favored electrical charge polarization. • Slight excess of iron oxide enhanced saturative magnetization behavior.

Binder Jetting: A Novel NdFeB Bonded Magnet Fabrication Process

Science.gov (United States)

Paranthaman, M. Parans; Shafer, Christopher S.; Elliott, Amy M.; Siddel, Derek H.; McGuire, Michael A.; Springfield, Robert M.; Martin, Josh; Fredette, Robert; Ormerod, John

2016-07-01

The goal of this research is to fabricate near-net-shape isotropic (Nd)2Fe14B-based (NdFeB) bonded magnets using a three dimensional printing process to compete with conventional injection molding techniques used for bonded magnets. Additive manufacturing minimizes the waste of critical materials and allows for the creation of complex shapes and sizes. The binder jetting process works similarly to an inkjet printer. A print-head passes over a bed of NdFeB powder and deposits a polymer binding agent to bind the layer of particles together. The bound powder is then coated with another layer of powder, building the desired shape in successive layers of bonded powder. Upon completion, the green part and surrounding powders are placed in an oven at temperatures between 100°C and 150°C for 4-6 h to cure the binder. After curing, the excess powder can be brushed away to reveal the completed "green" part. Green magnet parts were then infiltrated with a clear urethane resin to achieve the measured density of the magnet of 3.47 g/cm3 close to 46% relative to the NdFeB single crystal density of 7.6 g/cm3. Magnetic measurements indicate that there is no degradation in the magnetic properties. This study provides a new pathway for preparing near-net-shape bonded magnets for various magnetic applications.

Effect of {gamma}-ray irradiation on the magnetic properties of NdFeB and Fe-Cr-Co permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Gao, R.S. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhen, L. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)]. E-mail: zhenl@hit.edu.cn; Li, G.A. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xu, C.Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Shao, W.Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2006-07-15

The effect of {gamma}-ray irradiation on the magnetic properties of NdFeB and Fe-Cr-Co permanent magnets has been investigated. The magnetic flux loss of two kinds of magnets before and after irradiation was measured. Results show that the effect of {gamma}-ray irradiation on the magnetic properties of sintered NdFeB is not so obvious as that on Fe-Cr-Co magnet. Irradiation-induced damage from {gamma}-ray for the Fe-Cr-Co magnets was characterized for the first time. The decline of permanent magnetic properties of Fe-Cr-Co magnet induced by {gamma}-ray irradiation is reversible except for the maximum energy product (BH){sub max}. The difference of coercivity mechanism between these two kinds of permanent magnets is responsible for the different dependence of magnetic properties loss induced by {gamma}-ray irradiation.

Understanding the chemical vapor deposition of diamond: recent progress

International Nuclear Information System (INIS)

Butler, J E; Mankelevich, Y A; Cheesman, A; Ma, Jie; Ashfold, M N R

2009-01-01

In this paper we review and provide an overview to the understanding of the chemical vapor deposition (CVD) of diamond materials with a particular focus on the commonly used microwave plasma-activated chemical vapor deposition (MPCVD). The major topics covered are experimental measurements in situ to diamond CVD reactors, and MPCVD in particular, coupled with models of the gas phase chemical and plasma kinetics to provide insight into the distribution of critical chemical species throughout the reactor, followed by a discussion of the surface chemical process involved in diamond growth.

Microstructure and Magnetic Properties of NdFeB Films through Nd Surface Diffusion Process

Directory of Open Access Journals (Sweden)

Wenfeng Liu

2017-01-01

Full Text Available Ta/Nd/NdFeB/Nd/Ta films were deposited by magnetron sputtering on Si (100 substrates and subsequently annealed for 30 min at 923 K in vacuum. It was found that the microstructure and magnetic properties of Ta/Nd/NdFeB/Nd/Ta films strongly depend on the NdFeB layer thickness. With NdFeB layer thickness increasing, both the grain size and the strain firstly reduce and then increase. When NdFeB layer thickness is 750 nm, the strain reaches the minimum value. Meanwhile, both the in-plane and perpendicular coercivities firstly drastically increase and then slowly decrease with NdFeB layer thickness increasing. The highest in-plane and perpendicular coercivities can be obtained at NdFeB layer thickness of 750 nm, which are 21.2 kOe and 19.5 kOe, respectively. In addition, the high remanence ratio (remanent magnetization/saturation magnetization of 0.87 can also be achieved in Ta/Nd/NdFeB (750 nm/Nd/Ta film.

Fe3−δO4/MgO/Co magnetic tunnel junctions synthesized by full in situ atomic layer and chemical vapour deposition

International Nuclear Information System (INIS)

Mantovan, R; Vangelista, S; Kutrzeba-Kotowska, B; Lamperti, A; Fanciulli, M; Manca, N; Pellegrino, L

2014-01-01

Fe 3−δ O 4 /MgO/Co magnetic tunnel junctions (MTJs) are synthesized on top of ∼1 inch Si/SiO 2 substrates by conducting a full in situ chemical vapour and atomic layer deposition process with no vacuum break. Tunnel magnetoresistance up to 6% is measured at room temperature, increasing to 12.5% at 120 K. Our results demonstrate the possibility of using full-chemical processes to synthesize functional MTJs, and this could provide a path towards the use of cost-effective methods to produce magnetic devices on a large scale. (fast track communication)

Microstructure, magnetic and Moessbauer studies on spark-plasma sintered Sm-Co-Fe/Fe(Co) nanocomposite magnets

Energy Technology Data Exchange (ETDEWEB)

Rao, N V Rama; Saravanan, P; Gopalan, R; Raja, M Manivel; Rao, D V Sreedhara; Chandrasekaran, V [Defence Metallurgical Research Laboratory, Hyderabad-500 058 (India); Sivaprahasam, D [International Advanced Research Centre for Powder Metallurgy and New Materials Hyderabad-500 005 (India); Ranganathan, R [Saha Institute of Nuclear Physics, Kolkata-700 064 (India)], E-mail: rg_gopy@yahoo.com

2008-03-21

Nanocomposite powders comprising Sm-Co-Fe intermetallic phases and Fe(Co) were synthesized by high-energy ball milling and were consolidated into bulk magnets by the spark-plasma sintering (SPS) technique. While the microstructure of the SPS samples was characterized by transmission electron microscopy (TEM), the solubility of Fe in different phases was investigated using Moessbauer spectroscopy. TEM studies revealed that the spark-plasma sintered sample has Sm(Co,Fe){sub 5} as a major phase with Sm{sub 2}(Co,Fe){sub 17}, Sm(Co,Fe){sub 2} and Fe(Co) as secondary phases. The size of the nanocrystalline grains of all these phases was found to be in the range 50-100 nm. The Moessbauer spectra of the as-milled powders exhibited two different subspectra: a sextet corresponding to the Fe phase and a broad sextet associated with the Fe(Co) phase; while that of the SPS sample showed four different subspectra: a sextet corresponding to Fe and other three sextets corresponding to the Fe(Co), Sm(Co,Fe){sub 5} and Sm{sub 2}(Co,Fe){sub 17} phases; these results are in accordance with the TEM observation. Recoil magnetization and reversible susceptibility measurements revealed magnetically single phase behaviour of the SPS magnets.

Tuning the magnetism of the top-layer FeAs on BaFe2As2 (001): First-principles study

Science.gov (United States)

Zhang, Bing-Jing; Liu, Kai; Lu, Zhong-Yi

2018-04-01

Magnetism may play an important role in inducing the superconductivity in iron-based superconductors. As a prototypical system, the surface of BaFe2As2 provides a good platform for studying related magnetic properties. We have designed systematic first-principles calculations to clarify the surface magnetism of BaFe2As2 (001), which previously has received little attention in comparison with surface structures and electronic states. We find that the surface environment has an important influence on the magnetic properties of the top-layer FeAs. For As-terminated surfaces, the magnetic ground state of the top-layer FeAs is in the staggered dimer antiferromagnetic (AFM) order, distinct from that of the bulk, while for Ba-terminated surfaces the collinear (single-stripe) AFM order is the most stable, the same as that in the bulk. When a certain coverage of Ba or K atoms is deposited onto the As-terminated surface, the calculated energy differences among different AFM orders for the top-layer FeAs on BaFe2As2 (001) can be much reduced, indicating enhanced spin fluctuations. To compare our results with available scanning tunneling microscopy (STM) measurements, we have simulated the STM images of several structural/magnetic terminations. Astonishingly, when the top-layer FeAs is in the staggered dimer AFM order, a stripe pattern appears in the simulated STM image even when the surface Ba atoms adopt a √{2 }×√{2 } structure, while a √{2 }×√{2 } square pattern comes out for the 1 ×1 full As termination. Our results suggest: (i) the magnetic state at the BaFe2As2 (001) surface can be quite different from that in the bulk; (ii) the magnetic properties of the top-layer FeAs can be tuned effectively by surface doping, which may likely induce superconductivity at the surface layer; (iii) both the surface termination and the AFM order in the top-layer FeAs can affect the STM image of BaFe2As2 (001), which needs to be taken into account when identifying the surface

Characterization of bimetallic Fe/Pd nanoparticles by grape leaf aqueous extract and identification of active biomolecules involved in the synthesis

Energy Technology Data Exchange (ETDEWEB)

Luo, Fang; Yang, Die; Chen, Zuliang, E-mail: Zuliang.chen@newcastle.edu.au; Megharaj, Mallavarapu; Naidu, Ravi

2016-08-15

This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20 nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC–MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs. - Graphical abstract: TEM image for the Fe/Pd NPs synthesized by grape leaf aqueous extract. - Highlights: • The one-step green synthesis of Fe/Pd nanoparticles has been systematically characterized. • TEM showed that the Fe/Pd NPs were polydispersed with a diameter ranging from 2 to 20 nm. • Active biomolecules in the grape extract were identified.

Characterization of bimetallic Fe/Pd nanoparticles by grape leaf aqueous extract and identification of active biomolecules involved in the synthesis

International Nuclear Information System (INIS)

Luo, Fang; Yang, Die; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

2016-01-01

This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20 nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC–MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs. - Graphical abstract: TEM image for the Fe/Pd NPs synthesized by grape leaf aqueous extract. - Highlights: • The one-step green synthesis of Fe/Pd nanoparticles has been systematically characterized. • TEM showed that the Fe/Pd NPs were polydispersed with a diameter ranging from 2 to 20 nm. • Active biomolecules in the grape extract were identified.

Magnetic properties of FeNi-based thin film materials with different additives

KAUST Repository

Liang, C.; Gooneratne, C.P.; Wang, Q.X.; Liu, Y.; Gianchandani, Y.; Kosel, Jü rgen

2014-01-01

This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials

High magnetic coercivity of FePt-Ag/MgO granular nanolayers

Science.gov (United States)

Roghani, R.; Sebt, S. A.; Khajehnezhad, A.

2018-06-01

L10-FePt ferromagnetic nanoparticles have a hight coercivity of Tesla order. Thus, these nanoparticles, with size of 10 to 15 nm and uniform surface distribution, are suitable in magnetic data storage technology with density of more than 1GB. In order to improve structural and magnetic properties of FePt nanoparticles, some elements and combinations have been added to compound. In this research, we show that due to the presence of the Ag, the phase transition temperature of FePt from fcc to L10-fct phase decreases. The presence of Ag as an additive in FePt-Ag nanocomposite, increases the magnetic coercivity. This nanocomposite, with 10% Ag, was deposited by magnetron sputtering on the MgO heat layer. VSM results of 10 nm nanoparticles show that coercivity has increased up to 1.4 T. XRD and FESEM results confirm that the size of the L10-FePt nanoparticles are 10 nm and their surface distribution are uniform. Ag gradually form nano scale clusters with separate lattice and FePt-Ag nanocomposite appears. The result of this process is emptiness of Ag position in FePt-fcc lattice. So, the mobility of Fe and Pt atoms in this lattice increases and it can be possible for them to move in lower temperature. This mechanism explain the effect of Ag on decreasing the transition temperature to fct-L10 phase, and hight coercivity of FePt nanoparticles.

Flash vaporization during earthquakes evidenced by gold deposits

Science.gov (United States)

Weatherley, Dion K.; Henley, Richard W.

2013-04-01

Much of the world's known gold has been derived from arrays of quartz veins. The veins formed during periods of mountain building that occurred as long as 3 billion years ago, and were deposited by very large volumes of water that flowed along deep, seismically active faults. The veins formed under fluctuating pressures during earthquakes, but the magnitude of the pressure fluctuations and their influence on mineral deposition is not known. Here we use a simple thermo-mechanical piston model to calculate the drop in fluid pressure experienced by a fluid-filled fault cavity during an earthquake. The geometry of the model is constrained using measurements of typical fault jogs, such as those preserved in the Revenge gold deposit in Western Australia, and other gold deposits around the world. We find that cavity expansion generates extreme reductions in pressure that cause the fluid that is trapped in the jog to expand to a very low-density vapour. Such flash vaporization of the fluid results in the rapid co-deposition of silica with a range of trace elements to form gold-enriched quartz veins. Flash vaporization continues as more fluid flows towards the newly expanded cavity, until the pressure in the cavity eventually recovers to ambient conditions. Multiple earthquakes progressively build economic-grade gold deposits.

Controlling the resistivity gradient in chemical vapor deposition-deposited aluminum-doped zinc oxide

NARCIS (Netherlands)

Ponomarev, M. V.; Verheijen, M. A.; Keuning, W.; M. C. M. van de Sanden,; Creatore, M.

2012-01-01

Aluminum-doped ZnO (ZnO:Al) grown by chemical vapor deposition (CVD) generally exhibit a major drawback, i.e., a gradient in resistivity extending over a large range of film thickness. The present contribution addresses the plasma-enhanced CVD deposition of ZnO: Al layers by focusing on the control

Nd composition dependence of microstructure and magnetic properties for gradient sputtered NdFeB films

International Nuclear Information System (INIS)

Li Shandong; Wang Dawei; Fang Jianglin; Duh, J.-G.; Wang Yinying; Wu Yizhi; Huang Junheng; Zheng Hongjun

2008-01-01

NdFeB films with Nd compositions varied from 13.34 to 24.30 at% were deposited by DC gradient sputtering using targets Nd 12.5 Fe 71.5 B 16 and Nd. The hard magnetic properties, grain growth direction and magnetic domain structures were dramatically influenced by Nd composition. The samples with intermediate Nd concentrations exhibited optimal magnetic properties and microstructures, such as large squareness ratio over 0.9, large energy product up to 174 kJ/m 3 , and vertical domain structure. However, the samples with higher and lower Nd compositions showed almost isotropic loops. (0 0 l) as main X-ray diffraction peaks in the optimal Nd composition region indicated most of Nd 2 Fe 14 B grains with c-axis perpendicular to the film plane, while NdFeB grains in other region are almost random growth. The good magnetic properties can be attributed to the vertical growth of Nd 2 Fe 14 B grains

Nd composition dependence of microstructure and magnetic properties for gradient sputtered NdFeB films

Energy Technology Data Exchange (ETDEWEB)

Li Shandong [Department of Physics, Fujian Normal University, Fuzhou 350007 (China)], E-mail: dylsd007@yahoo.com.cn; Wang Dawei [Department of Physics, Fujian Normal University, Fuzhou 350007 (China); Fang Jianglin [Center for Materials Analysis, Nanjing University, Nanjing 210093 (China); Duh, J.-G. [Department of Materials Science and Engineering, National TsingHua Universtiy, Hsinchu, Taiwan (China); Wang Yinying; Wu Yizhi; Huang Junheng; Zheng Hongjun [Department of Physics, Fujian Normal University, Fuzhou 350007 (China)

2008-08-15

NdFeB films with Nd compositions varied from 13.34 to 24.30 at% were deposited by DC gradient sputtering using targets Nd{sub 12.5}Fe{sub 71.5}B{sub 16} and Nd. The hard magnetic properties, grain growth direction and magnetic domain structures were dramatically influenced by Nd composition. The samples with intermediate Nd concentrations exhibited optimal magnetic properties and microstructures, such as large squareness ratio over 0.9, large energy product up to 174 kJ/m{sup 3}, and vertical domain structure. However, the samples with higher and lower Nd compositions showed almost isotropic loops. (0 0 l) as main X-ray diffraction peaks in the optimal Nd composition region indicated most of Nd{sub 2}Fe{sub 14}B grains with c-axis perpendicular to the film plane, while NdFeB grains in other region are almost random growth. The good magnetic properties can be attributed to the vertical growth of Nd{sub 2}Fe{sub 14}B grains.

Growth of carbon nanotubes by Fe-catalyzed chemical vapor processes on silicon-based substrates

Science.gov (United States)

Angelucci, Renato; Rizzoli, Rita; Vinciguerra, Vincenzo; Fortuna Bevilacqua, Maria; Guerri, Sergio; Corticelli, Franco; Passini, Mara

2007-03-01

In this paper, a site-selective catalytic chemical vapor deposition synthesis of carbon nanotubes on silicon-based substrates has been developed in order to get horizontally oriented nanotubes for field effect transistors and other electronic devices. Properly micro-fabricated silicon oxide and polysilicon structures have been used as substrates. Iron nanoparticles have been obtained both from a thin Fe film evaporated by e-gun and from iron nitrate solutions accurately dispersed on the substrates. Single-walled nanotubes with diameters as small as 1 nm, bridging polysilicon and silicon dioxide “pillars”, have been grown. The morphology and structure of CNTs have been characterized by SEM, AFM and Raman spectroscopy.

Effect of Different Catalyst Deposition Technique on Aligned Multiwalled Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

Directory of Open Access Journals (Sweden)

Mohamed Shuaib Mohamed Saheed

2014-01-01

Full Text Available The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysis revealed that aligned multiwalled carbon nanotubes array of 107.9 µm thickness grown by thermal chemical vapor deposition technique can only be achieved for the sample with iron deposited using ferrocene vaporization. The thick layer of partially oxidized iron film can prevent the deactivation of catalyst and thus is able to sustain the growth. It also increases the rate of permeation of the hydrocarbon gas into the catalyst particles and prevents agglomeration at the growth temperature. Combination of alumina-iron layer provides an efficient growth of high density multiwalled carbon nanotubes array with the steady growth rate of 3.6 µm per minute for the first 12 minutes and dropped by half after 40 minutes. Thicker and uniform iron catalyst film obtained from ferrocene vaporization is attributed to the multidirectional deposition of particles in the gaseous form.

Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers

Energy Technology Data Exchange (ETDEWEB)

Miko, Annamaria [Bay Zoltan Institute for Material Science (Hungary); Kuzmann, Erno, E-mail: kuzmann@para.chem.elte.hu [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Lakatos-Varsanyi, Magda [Bay Zoltan Institute for Material Science (Hungary); Kakay, Attila [Research Institute for Solid State Physics and Optics (Hungary); Nagy, Ferenc [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Varga, Lajos Karoly [Research Institute for Solid State Physics and Optics (Hungary)

2005-09-15

{sup 57}Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and {sup 57}Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t{sub on} = 2 ms), with short relaxation time (t{sub off} = 9 ms) and low current density (I{sub p} = 0.05 Acm{sup -2}) or at short deposition time (t{sub on} = 1 ms) with long relaxation time (t{sub off} = 250 ms) and high current density (I{sub p} = 1.0 Acm{sup -2}). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-06-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

The magnetic properties of Ce/Pd surface alloys investigated using DFT

KAUST Repository

Shuttleworth, I.G.

2014-01-01

The surface alloys that form between Ce and Pd(1 1 1), Pd(1 0 0) and both unreconstructed and missing-row type Pd(1 1 0) at low Ce coverage ( θCe=19ML) have shown permanent magnetism that is mediated in part by an RKKY-like delocalized Ce 6s-Pd 5s interaction. The Pd 4d states are significantly affected by alloying and their behavior cannot be explained by a purely spin-dependent Hamiltonian. Experimental observations of changes to the Pd 4d states are explained and the implications of Ce/Pd magnetism in reforming catalysis are discussed. © 2014 Elsevier B.V. All rights reserved.

Growth of Pd-Filled Carbon Nanotubes on the Tip of Scanning Probe Microscopy

Directory of Open Access Journals (Sweden)

Tomokazu Sakamoto

2009-01-01

Full Text Available We have synthesized Pd-filled carbon nanotubes (CNTs oriented perpendicular to Si substrates using a microwave plasma-enhanced chemical vapor deposition (MPECVD for the application of scanning probe microscopy (SPM tip. Prior to the CVD growth, Al thin film (10 nm was coated on the substrate as a buffer layer followed by depositing a 5∼40 nm-thick Pd film as a catalyst. The diameter and areal density of CNTs grown depend largely on the initial Pd thickness. Scanning electron microscopy (SEM and transmission electron microscopy (TEM images clearly show that Pd is successfully encapsulated into the CNTs, probably leading to higher conductivity. Using optimum growth conditions, Pd-filled CNTs are successfully grown on the apex of the conventional SPM cantilever.

3D magnetic nanostructures grown by focused electron and ion beam induced deposition

Science.gov (United States)

Fernandez-Pacheco, Amalio

Three-dimensional nanomagnetism is an emerging research area, where magnetic nanostructures extend along the whole space, presenting novel functionalities not limited to the substrate plane. The development of this field could have a revolutionary impact in fields such as electronics, the Internet of Things or bio-applications. In this contribution, I will show our recent work on 3D magnetic nanostructures grown by focused electron and ion beam induced deposition. This 3D nano-printing techniques, based on the local chemical vapor deposition of a gas via the interaction with electrons and ions, makes the fabrication of complex 3D magnetic nanostructures possible. First, I will show how by exploiting different growth regimes, suspended Cobalt nanowires with modulated diameter can be patterned, with potential as domain wall devices. Afterwards, I will show recent results where the synthesis of Iron-Gallium alloys can be exploited in the field of artificial multiferroics. Moreover, we are developing novel methodologies combining physical vapor deposition and 3D nano-printing, creating Permalloy 3D nanostrips with controllable widths and lengths up to a few microns. This approach has been extended to more complex geometries by exploiting advanced simulation growth techniques combining Monte Carlo and continuum model methods. Throughout the talk, I will show the methodology we are following to characterize 3D magnetic nanostructures, by combining magneto-optical Kerr effect, scanning probe microscopy and electron and X-R magnetic imaging, and I will highlight some of the challenges and opportunities when studying these structures. I acknowledge funding from EPSRC and the Winton Foundation.

Epitactical FeAl films on sapphire and their magnetic properties; Epitaktische FeAl-Filme auf Saphir und ihre magnetischen Eigenschaften

Energy Technology Data Exchange (ETDEWEB)

Trautvetter, Moritz

2011-05-05

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{sup +} 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.)

Spin-orbit driven phenomena in the isoelectronic L1.sub.0./sub.-Fe(Pd,Pt) alloys from first principles

Czech Academy of Sciences Publication Activity Database

Kudrnovský, Josef; Drchal, Václav; Turek, Ilja

2017-01-01

Roč. 96, č. 21 (2017), s. 1-7, č. článku 214437. ISSN 2469-9950 R&D Projects: GA ČR GA15-13436S Institutional support: RVO:68378271 ; RVO:68081723 Keywords : anomalous Hall effect * Gilbert damping * partial order * first-principles * Fe(Pd,Pt) alloys Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

Degradation of γ-HCH spiked soil using stabilized Pd/Fe0 bimetallic nanoparticles: Pathways, kinetics and effect of reaction conditions

International Nuclear Information System (INIS)

Singh, Ritu; Misra, Virendra; Mudiam, Mohana Krishna Reddy; Chauhan, Lalit Kumar Singh; Singh, Rana Pratap

2012-01-01

Highlights: ► This study explores the potential of CMC-Pd/nFe 0 to degrade γ-HCH in spiked soil. ► Sorption–desorption characteristics and partitioning of γ-HCH is investigated. ► Three degradation pathways has been proposed and discussed. ► γ-HCH degradation mechanism and kinetics is elucidated. ► Activation energy reveals that γ-HCH degradation is a surface mediated reaction. - Abstract: This study investigates the degradation pathway of gamma-hexachlorocyclohexane (γ-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe 0 bimetallic nanoparticles (CMC-Pd/nFe 0 ). GC–MS analysis of γ-HCH degradation products showed the formation of pentachlorocyclohexene, tri- and di-chlorobenzene as intermediate products while benzene was formed as the most stable end product. On the basis of identified intermediates and final products, degradation pathway of γ-HCH has been proposed. Batch studies showed complete γ-HCH degradation at a loading of 0.20 g/L CMC-Pd/nFe 0 within 6 h of incubation. The surface area normalized rate constant (k SA ) was found to be 7.6 × 10 −2 L min −1 m −2 . CMC-Pd/nFe 0 displayed ∼7-fold greater efficiency for γ-HCH degradation in comparison to Fe 0 nanoparticles (nFe 0 ), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe 0 loading and reaction temperature facilitates γ-HCH degradation, whereas a declining trend in degradation was noticed with the increase in pH, initial γ-HCH concentration and in the presence of cations. The data on activation energy (33.7 kJ/mol) suggests that γ-HCH degradation is a surface mediated reaction. The significance of the study with respect to remediation of γ-HCH contaminated soil using CMC-Pd/nFe 0 has been discussed.

Sensing performance of plasma-enhanced chemical vapor deposition SiC-SiO2-SiC horizontal slot waveguides

NARCIS (Netherlands)

Pandraud, G.; Margallo-Balbas, E.; Sarro, P.M.

2012-01-01

We have studied, for the first time, the sensing capabilities of plasma-enhanced chemical vapor deposition (PECVD) SiC-SiO2-SiC horizontal slot waveguides. Optical propagation losses were measured to be 23.9 dB?cm for the quasi-transverse magnetic mode. To assess the potential of this device as a

Structure and magnetism in Co/X, Fe/Si, and Fe/(FeSi) multilayers

Science.gov (United States)

Franklin, Michael Ray

Previous studies have shown that magnetic behavior in multilayers formed by repeating a bilayer unit comprised of a ferromagnetic layer and a non-magnetic spacer layer can be affected by small structural differences. For example, a macroscopic property such as giant magnetoresistance (GMR) is believed to depend significantly upon interfacial roughness. In this study, several complimentary structural probes were used to carefully characterize the structure of several sputtered multilayer systems-Co/Ag, Co/Cu, Co/Mo, Fe/Si, and Fe//[FeSi/]. X-ray diffraction (XRD) studies were used to examine the long-range structural order of the multilayers perpendicular to the plane of the layers. Transmission electron diffraction (TED) studies were used to probe the long-range order parallel to the layer plane. X-ray Absorption Fine Structure (XAFS) studies were used to determine the average local structural environment of the ferromagnetic atoms. For the Co/X systems, a simple correlation between crystal structure and saturation magnetization is discovered for the Co/Mo system. For the Fe/X systems, direct evidence of an Fe-silicide is found for the /[FeSi/] spacer layer but not for the Si spacer layer. Additionally, differences were observed in the magnetic behavior between the Fe in the nominally pure Fe layer and the Fe contained in the /[FeSi/] spacer layers.

Permanent magnetic properties of NdFe12Nx sputtered films epitaxially grown on V buffer layer

Science.gov (United States)

Sato, T.; Ohsuna, T.; Yano, M.; Kato, A.; Kaneko, Y.

2017-08-01

To clarify the magnetic properties of the NdFe12Nx compound, which shows promise as a high-performance permanent magnet material, NdFe12Nx epitaxial films fabricated by using a V underlayer on MgO (100) single-crystalline substrates were investigated. Nd-Fe films deposited on a V underlayer consist of NdFe12 grains, which have a c-axis orientation perpendicular to the film plane, as well as α-Fe and Nd2Fe17 phases. In the Nd-Fe-N film obtained by subsequent nitridation of the Nd-Fe film, NdFe12Nx grains grew as the dominant phase, and the volume fractions of α-Fe phases dropped below 5%. A Nd-Fe-N film with a thickness of 50 nm exhibits a saturation magnetization (Ms) of 1.7 T, an anisotropy field (HA) of ˜60 kOe, a magnetocrystalline anisotropy energy (K1) of ˜4.1 MJ/m3, and a coercivity (Hc) of 1.7 kOe. The Hc of a Nd-Fe-N film with a thickness of 25 nm is 4.3 kOe. These results indicate that NdFe12Nx compounds have a superior Ms compared to Nd-Fe-B magnets, while the enhancement in Hc is indispensable.