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7 May 2013

Volume 113, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 174302 (2013); http://dx.doi.org/10.1063/1.4798262 (4 pages)

Yuichiro Kurokawa, Takehiko Hihara, and Ikuo Ichinose
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Preface: Proceedings of the 12th Joint MMM–Intermag Conference, 14–18 January 2013, Chicago, IL, USA

Paul Crowell

J. Appl. Phys. 113, 17A101 (2013); http://dx.doi.org/10.1063/1.4803120 (1 page)

Online Publication Date: 24 April 2013

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Abstract Unavailable
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01.30.Ww Editorials
back to top Soft Magnetic Materials

Effects of FeCo magnetic nanoparticles on microstructure of Sn-Ag-Cu alloys

Siyang Xu, Ashfaque H. Habib, Anya Prasitthipayong, and Michael E. McHenry

J. Appl. Phys. 113, 17A301 (2013); http://dx.doi.org/10.1063/1.4793502 (3 pages)

Online Publication Date: 26 February 2013

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Sn-Ag-Cu (SAC) alloys have been regarded as the most promising candidates for lead-free solders in the electronic packaging industry. We prepared SAC solder-FeCo magnetic nanoparticles (MNPs) composite paste with different MNP concentration and used AC magnetic fields localized heating to cause their reflow. Differential scanning calorimetry results show a reduced undercooling of the composite paste with the addition of MNPs. Transmission electron microscope prove that the FeCo MNPs are distributed in Sn matrix of the reflowed solder composites. Optical micrographs show a decrease in the amount of primary Ag3Sn and β-Sn dendrites, and an increase in the amount of eutectic microconstituents with increasing MNPs. The addition of FeCo MNPs is considered to promote the solidification of β-Sn by providing more heterogeneous nucleation sites at a relatively low undercooling, which results in the microstructural refinement in the as-prepared solder joints.
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81.20.Vj Joining; welding
81.40.Gh Other heat and thermomechanical treatments
06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials

An integrated inductor for high current with using Fe-Si metal alloy composite films

Sung Tae Lim, Hee-Jun Kim, In Bum Jeong, Tae Kyeong Lee, and Hee Hwang

J. Appl. Phys. 113, 17A302 (2013); http://dx.doi.org/10.1063/1.4793607 (3 pages)

Online Publication Date: 27 February 2013

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An integrated inductor, using 0.1 mm Fe-Si alloy composite films, has been developed with a dimension of 4.8 mm × 4.5 mm × 1.0 mm thickness. The developed inductor is structured by stacking of metal alloy composite films with μR = 19.5, which consist of mixed Fe-Si alloy powders and epoxy resin for high current application. These stacked films have an etched spiral copper trace with 9 and quarter turns for 4 layers on each film. Copper trace is patterned with a dimension of 0.07 mm thickness, 0.45 mm width, and 1 mm pitch using photolithography technology. In order to evaluate the performance of the developed inductor, inductance and DC resistance were simulated and measured. The simulated result of 1.05 μH and 83 mΩ is well coincided with measured results of 1 μH and 88 mΩ. It is also confirmed that the inductor has a high current capacity of 3 A rated and 6 A saturated values. As an application, a synchronous step down DC-DC converter using the developed inductor is fabricated with the output power of 6.6 W (3.3 V/2 A) and the switching frequency of 3 MHz. Finally, the maximum efficiency of 87% is achieved from the experiment of this DC-DC converter.
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84.32.Hh Inductors and coils; wiring
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.30.Jc Power electronics; power supply circuits

Microstructures and magnetostrictive strains of Fe-Ga-Ni ferromagnetic shape memory alloys

Yin-Chih Lin

J. Appl. Phys. 113, 17A303 (2013); http://dx.doi.org/10.1063/1.4793609 (3 pages)

Online Publication Date: 27 February 2013

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Transmission electron microscopy (TEM), a magnetostrictive-meter setup, and a superconducting quantum interference device magnetometer were used to investigate the microstructures, saturation magnetostriction, and magnetic properties of bulk Fe81Ga19 and Fe73Ga19Ni8 (at. %) ferromagnetic shape memory alloys (FSMAs). In the Fe81Ga19 FSMA, after solution treatment (ST) at 1100 °C for 4 h and quenching in ice brine, the antiphase boundary segments of the D03 domain were observed in the A2 (disordered) matrix. When the Fe81Ga19 FSMA was solution treated and aged at 750 °C for 24 h and then furnace cooled (FC), the A2 + D03 phase transformed into A2 + B2 + D03 structures, accompanied by coarse B2 + D03 precipitates in the A2 matrix. This result decreased the saturation magnetostriction of the aged Fe81Ga19 FSMA. However, adding more Ni to the Fe81−xGa19Nix (x = 8 at. % Ni) FSMAs enhanced the formation of B2 + D03 structures, further decreased the saturation magnetostriction, and destroyed the ferromagnetic shape memory effect in Fe73Ga19Ni8 FSMA ST, aged at 750 °C for 24 h, and FC.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Bb Fe and its alloys
81.30.Kf Martensitic transformations
62.20.fg Shape-memory effect; yield stress; superelasticity
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.40.Gh Other heat and thermomechanical treatments
75.78.Fg Dynamics of domain structures

Domain wall mobility in rapidly solidified ultrathin amorphous wires

T.-A. Óvári and H. Chiriac

J. Appl. Phys. 113, 17A304 (2013); http://dx.doi.org/10.1063/1.4793641 (3 pages)

Online Publication Date: 27 February 2013

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Results on the complex relation between magnetic domain wall mobility and magnetic anisotropy in rapidly solidified amorphous submicron wires and nanowires are reported. A distinctly nonlinear dependence of the domain wall mobility on wire diameter has been found in the case of positive magnetostrictive wires, whilst the same dependence is monotonic in the case of nearly zero magnetostrictive ones. This significant difference has been proven to originate in the different types of magnetic anisotropy, which exist in thin amorphous wires having different signs and magnitudes of the magnetostriction.
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75.60.Ch Domain walls and domain structure
81.30.Fb Solidification
75.30.Gw Magnetic anisotropy
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Tt Fine-particle systems; nanocrystalline materials

Modeling of localized reflow in solder/magnetic nanocomposites for area-array packaging

Siyang Xu, Andrea D. Pickel, Anya Prasitthipayong, Ashfaque H. Habib, and Michael E. McHenry

J. Appl. Phys. 113, 17A305 (2013); http://dx.doi.org/10.1063/1.4793516 (3 pages)

Online Publication Date: 4 March 2013

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We have modeled the reflow process of FeCo magnetic nanoparticle (MNP)-based solder composites with eddy current power loss of substrate and magnetic power losses of solder bumps. For an area array package without MNPs when subjected to 300 kHz ac magnetic field, the eddy current power loss can result in excessive temperatures that can cause substrate damage. Temperature profiles with different MNP concentration were simulated and the results showed localized reflow of solders to enable low-temperature assembly. The temperatures at different times and positions in solder composites were analyzed. We also modeled thermal profiles for solder composites with 0.2 wt. % MNP in 1 MHz and 3 MHz magnetic field. Such high field frequency generated larger power losses in MNPs and is shown to increase the heating efficiency.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.07.Wx Nanopowders

Reduced losses in rolled Fe73.5Si15.5Nb3B7Cu1 nanocrystalline ribbon

S. J. Kernion, M. S. Lucas, J. Horwath, Z. Turgut, E. Michel, V. Keylin, J. F. Huth, A. M. Leary, S. Shen, and M. E. McHenry

J. Appl. Phys. 113, 17A306 (2013); http://dx.doi.org/10.1063/1.4794131 (3 pages)

Online Publication Date: 6 March 2013

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Eddy currents in magnetic components undergoing high frequency switching can be mitigated by reducing the thickness of the component. Planar flow cast Fe73.5Si15.5Nb3B7Cu1 ribbon was plastically deformed by cold rolling, resulting in a thickness reduction of 38%. Shear band formation was seen and the coercivity was dramatically higher in the rolled ribbon. After crystallization, the hysteresis loop of the rolled ribbon was nearly identical to a non-rolled ribbon and losses were lower in the rolled ribbon above 25 kHz. Reductions in thickness by this method can lead to increases in operating frequency for power conversion applications.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
75.78.Jp Ultrafast magnetization dynamics and switching
72.30.+q High-frequency effects; plasma effects
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

Francis Johnson, Thomas R. Raber, Robert J. Zabala, Steve J. Buresh, and Brian Tanico

J. Appl. Phys. 113, 17A307 (2013); http://dx.doi.org/10.1063/1.4793610 (3 pages)

Online Publication Date: 7 March 2013

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Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 μΩ cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.
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81.05.Bx Metals, semimetals, and alloys
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.10.Fq Growth from melts; zone melting and refining
72.80.Tm Composite materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Phonon densities of states of face-centered-cubic Ni-Fe alloys

M. S. Lucas, L. Mauger, J. A. Muñoz, I. Halevy, J. Horwath, S. L. Semiatin, S. O. Leontsev, M. B. Stone, D. L. Abernathy, Yuming Xiao, Paul Chow, and B. Fultz

J. Appl. Phys. 113, 17A308 (2013); http://dx.doi.org/10.1063/1.4794354 (3 pages)

Online Publication Date: 8 March 2013

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Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to determine the phonon densities of states of face-centered-cubic Ni-Fe alloys. Increasing Fe concentration results in an average softening of the phonon modes. Chemical ordering of the Ni0.72Fe0.28 alloy results in a reduction of the partial vibrational entropy of the Fe atoms but does not significantly change the partial vibrational entropy of the Ni atoms. Changes in the phonon densities of states with composition and chemical ordering are discussed and analyzed with a cluster expansion method.
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63.20.dd Measurements
65.40.gd Entropy
78.70.Ck X-ray scattering

Tailoring of the soft magnetic property and uniaxial anisotropy of magnetostrictive films by interlayer

Dandan Wen, Feiming Bai, Yicheng Wang, Zhiyong Zhong, and Huaiwu Zhang

J. Appl. Phys. 113, 17A309 (2013); http://dx.doi.org/10.1063/1.4794403 (3 pages)

Online Publication Date: 8 March 2013

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Laminated amorphous FeSiBC films with various spacer layers, including Cu, Co0.45Cu0.55, Co0.8Cu0.2, and CoFe, were prepared in order to study the effect of interface structure and magnetic exchange interaction on the magnetic softness and uniaxial anisotropy of multilayered film. It is found that laminating FeSiBC film with thin nonmagnetic or weak magnetic spacers yields much lower coercivity and higher remanent magnetization than those with magnetic spacers. Optimal films with the desired properties of Hc ∼ 1.5 Oe, Mr/Ms = 95%, and Hk ∼ 16 Oe were obtained. Therefore, it is confirmed that the exchange interaction constant of spacer layer plays a more important role than that of interface structure. Furthermore, laminating FeSiBC with nonmagnetic layers only slightly changes magnetostrictive coefficient.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetic permeability of Si-rich (FeCoNi)-based nanocrystalline alloy: Thermal stability in a wide temperature range

Jia Wang, Zhi Wang, Yun-yun Jia, Rui-min Shi, Zhuan-ping Wen, and Hui-juan Kang

J. Appl. Phys. 113, 17A310 (2013); http://dx.doi.org/10.1063/1.4794718 (3 pages)

Online Publication Date: 11 March 2013

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Structure and magnetic properties of as-quenched and annealed Ni5(Fe0.5Co0.5)68.5Si17.5Nb3B5Cu1 alloys were investigated by differential scanning calorimetry, x-ray diffraction, transmission electron microscopy, and the temperature dependence of initial permeability (μi-T curves) from room temperature up to 680 °C. The as-quenched sample exhibits a higher secondary crystallization temperature (Tx2) and a larger crystallized interval temperature (ΔTx = Tx2−Tx1) for precipitating the single soft magnetic crystal phase. Annealing temperature (Ta) exerts a significant effect on room- and high-temperature μi for samples heating-cooling cycled at 510–680 °C. When Ta is at 640 °C, an excellent high temperature magnetic softness was observed in a wider temperature range, and the μi above 1000 at 10 KHz can keep up to 600 °C. The origin of this improved high-temperature magnetic softness was also analyzed.
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75.75.-c Magnetic properties of nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Magnetic properties and structure of Fe83.3–85.8B7.0–4.5P9Cu0.7 nanocrystalline alloys

Akiri Urata, Makoto Yamaki, Kaoru Satake, Hiroyuki Matsumoto, and Akihiro Makino

J. Appl. Phys. 113, 17A311 (2013); http://dx.doi.org/10.1063/1.4794377 (3 pages)

Online Publication Date: 12 March 2013

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The effects of Fe content on the magnetic properties and fine structure of the nanocrystalline Fe-B-P-Cu alloys have been investigated, with the objective of enhancing their magnetic softness. The nanocrystalline Fe83.3+xB7−xP9Cu0.7 (x = 0.0–2.5) alloys annealed at 673 K consist of uniform α-Fe grains embedded in a residual amorphous phase, and the average α-Fe grain diameter decreases from 18.1 to 14.6 nm with increasing Fe content. At the same time, the saturation magnetic flux density (Bs) increases and the coercivity (Hc) decreases with increasing Fe content and the x = 1.0 alloy has a high Bs of 1.72 T and a low Hc of 2.9 A/m. At x = 2.0 or higher, however, Hc drastically deteriorates from the effect of the coarse α-Fe grains. The core loss (W) of the x = 1.0 alloy at 50 Hz-1.6 T is 0.26 W/kg, which is one-third of that for oriented magnetic steel. These results indicate that the magnetic properties and structure of nanocrystalline Fe-B-P-Cu alloys are strongly affected by Fe content.
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75.75.-c Magnetic properties of nanostructures
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
61.46.Hk Nanocrystals
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
Author Select

Magnetization kinetics in tension and field annealed Fe-based amorphous alloys

Ryusuke Hasegawa, Kengo Takahashi, Bruno Francoeur, and Pierre Couture

J. Appl. Phys. 113, 17A312 (2013); http://dx.doi.org/10.1063/1.4794982 (3 pages)

Online Publication Date: 14 March 2013

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Magnetization kinetics in tension-annealed and field-annealed amorphous magnetic materials indicates that strain and magnetic fields are equally effective in inducing and relaxing local structural and magnetic anisotropy changes. This observation is based on the thermomagnetic aging of the magnetic properties obtained in the materials studied.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
72.15.Jf Thermoelectric and thermomagnetic effects
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.40.Gh Other heat and thermomechanical treatments

Characterization of as-synthesized FeCo magnetic nanoparticles by coprecipitation method

Jinu Kim, Jinbae Kim, Jongryoul Kim, and Ki Hyeon Kim

J. Appl. Phys. 113, 17A313 (2013); http://dx.doi.org/10.1063/1.4795321 (3 pages)

Online Publication Date: 14 March 2013

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FeCo nanoparticles were synthesized by a coprecipitation method without any post treatments. The structure, morphology, and magnetic properties of the FeCo nanoparticles formed at different sodium borohydride reaction times (5, 10, 20, and 30 min) were examined. X-ray diffraction revealed the representative α-FeCo peaks in all samples. The mean crystalline sizes slightly decreased from 31 nm to 21 nm with increasing reducing agent reaction time. A maximum saturation magnetization of 204 emu/g at 300 K was obtained in the sample with a reaction time of 5 min.
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75.75.Cd Fabrication of magnetic nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing

Strain effects in epitaxial Mn2O3 thin film grown on MgO(100)

Dang Duc Dung, Duong Van Thiet, Duong Anh Tuan, and Sunglae Cho

J. Appl. Phys. 113, 17A314 (2013); http://dx.doi.org/10.1063/1.4794720 (3 pages)

Online Publication Date: 18 March 2013

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We report on the epitaxial growth and magnetic properties of Mn2O3 thin films grown on MgO(001) substrate by molecular beam epitaxy. We observed the reduction in binding energy of Mn valence states, the increase in satellite separation up to 12.7 eV, and the smaller band gap of 3.32 eV. In addition, the antiferromagnetic ordering below 90 K in bulk changed to ferrimagnetic up to 175 K. The results were possibly to be explained by a lattice mismatch strain on Mn2O3 film on MgO(001) substrate.
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75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.at Other materials
68.60.Bs Mechanical and acoustical properties
75.50.Ee Antiferromagnetics
75.50.Gg Ferrimagnetics

Microwave absorbing characteristics of flake-shaped FeNiMo/epoxy composites

R. B. Yang and W. F. Liang

J. Appl. Phys. 113, 17A315 (2013); http://dx.doi.org/10.1063/1.4794721 (3 pages)

Online Publication Date: 19 March 2013

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Water atomized Fe16Ni82Mo2 (wt. %) alloy powder with spherical-like form was processed in a planetary mill for 2 h and 4 h, respectively. The complex permittivity (ε′−jε″) and permeability (μ′−jμ″) are measured using the transmission/reflection method in the frequency range of 2–18 GHz for FeNiMo/epoxy composites with 70 wt. % of magnetic fillers. The results show that all ε′, ε″, μ′, μ″ substantially increase due to the increase of aspect ratios. The magnetic susceptibility (μ′−1) of FeNiMo/epoxy absorber is negative above 5 GHz due to the natural magnetic resonance. The frequency dispersion of μ″ of flake-shaped FeNiMo composite shows a higher resonance frequency which exceeds the Snoek's limit in the gigahertz range as a result of large shape anisotropy. For composite absorbers with 2 mm thickness, the calculated reflection loss reaches −12.1 dB at 14.6 GHz without milling, −20.4 dB at 13.0 GHz for 2 h milling, and −13.1 dB at 11.0 GHz for 4 h milling.
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81.05.Qk Reinforced polymers and polymer-based composites
81.20.Wk Machining, milling
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)

Magnetic and high frequency properties of nanogranular CoFe-TiO2 films

Yicheng Wang, Huaiwu Zhang, Dandan Wen, Zhiyong Zhong, and Feiming Bai

J. Appl. Phys. 113, 17A316 (2013); http://dx.doi.org/10.1063/1.4795325 (3 pages)

Online Publication Date: 19 March 2013

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A series of soft magnetic nanogranular CoFe-TiO2 films with different thicknesses were fabricated on Si substrates by co-sputtering CoFe and TiO2, and the magnetic and high frequency properties were studied in details. X-ray diffraction analysis confirmed that the films were nanocrystalline/amorphous composites. A saturation magnetization as high as 21 kGs and a ferromagnetic resonance (FMR) frequency above 3 GHz were obtained. It was found that the coercivity decreased steeply with the increase of film thickness and its minimum value was about 6 Oe. In addition, the variations of FMR peak broadness of the imaginary part and damping factor were also presented and discussed as functions of film thickness.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
81.15.Cd Deposition by sputtering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

The influence of pressure on the phase stability of nanocomposite Fe89Zr7B4 during heating from energy dispersive x-ray diffraction

A. M. Leary, M. S. Lucas, P. R. Ohodnicki, S. J. Kernion, L. Mauger, C. Park, C. Kenney-Benson, and M. E. McHenry

J. Appl. Phys. 113, 17A317 (2013); http://dx.doi.org/10.1063/1.4795326 (3 pages)

Online Publication Date: 20 March 2013

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Nanocomposite materials consisting of small crystalline grains embedded within an amorphous matrix show promise for many soft magnetic applications. The influence of pressure is investigated by in situ diffraction of hammer milled Fe89Zr7B4 during heating through the α → γ Fe transition at 0.5, 2.2, and 4.9 GPa. The changes in primary and secondary crystallization onset are described by diffusion and the energy to form a critical nucleus within the framework of classical nucleation theory.
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64.70.kd Metals and alloys
68.35.Fx Diffusion; interface formation
81.40.Gh Other heat and thermomechanical treatments
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
62.50.-p High-pressure effects in solids and liquids
64.60.qj Studies of nucleation in specific substances

Tailoring of domain wall dynamics in amorphous microwires by annealing

K. Chichay, V. Zhukova, V. Rodionova, M. Ipatov, A. Talaat, J. M. Blanco, J. Gonzalez, and A. Zhukov

J. Appl. Phys. 113, 17A318 (2013); http://dx.doi.org/10.1063/1.4795617 (3 pages)

Online Publication Date: 20 March 2013

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We studied the effect of annealing on the magnetic properties and domain wall (DW) dynamics of magnetically bistable, Fe-based, glass-covered microwires with two different compositions, and different diameters. We observed the correlation of the domain wall dynamics with the distribution of the nucleation fields, measured in as-prepared samples, and after annealing for up to 150 min at temperatures of 250 and 300 °C. We found that both DW velocity and the range of the field limiting the single DW dynamics changed after annealing.
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75.60.Ch Domain walls and domain structure
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Gh Other heat and thermomechanical treatments
75.78.Fg Dynamics of domain structures
75.50.Bb Fe and its alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials

Semi-physical parameter identification for an iron-loss formula allowing loss-separation

S. Steentjes, M. Leßmann, and K. Hameyer

J. Appl. Phys. 113, 17A319 (2013); http://dx.doi.org/10.1063/1.4795618 (3 pages)

Online Publication Date: 20 March 2013

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This paper presents a semi-physical parameter identification for a recently proposed enhanced iron-loss formula, the IEM-Formula. Measurements are performed on a standardized Epstein frame by the conventional field-metric method under sinusoidal magnetic flux densities up to high magnitudes and frequencies. Quasi-static losses are identified on the one hand by point-by-point dc-measurements using a flux-meter and on the other hand by extrapolating higher frequency measurements to dc magnetization using the statistical loss-separation theory (Jacobs et al., “Magnetic material optimization for hybrid vehicle PMSM drives,” in Inductica Conference, CD-Rom, Chicago/USA, 2009). Utilizing this material information, possibilities to identify the parameter of the IEM-Formula are analyzed. Along with this, the importance of excess losses in present-day non-grain oriented Fe-Si laminations is investigated. In conclusion, the calculated losses are compared to the measured losses.
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84.50.+d Electric motors

Effect of magnetic field annealing on magnetic properties for nanocrystalline (Fe1−xCox)78.4Si9B9Nb2.6Cu1 alloys

Zhuan-ping Wen, Zhi Wang, Rui-min Shi, Jia Wang, and Hao Zhang

J. Appl. Phys. 113, 17A320 (2013); http://dx.doi.org/10.1063/1.4795620 (3 pages)

Online Publication Date: 20 March 2013

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The crystalline volume fraction Vcry, saturation magnetostriction λs, effective magnetic anisotropy 〈K〉, and temperature dependence of initial permeability (μi-T curves) for magnetic and nonmagnetic annealed (Fe1−xCox)78.4Si9B9Nb2.6Cu1 (x = 0.35, 0.5, 0.65, 1) alloys were investigated. The results showed that the magnetic annealing can enhance the Vcry and significantly reduce the λs. The Co content has an obvious effect on the λs and 〈K〉, the largest 〈K〉 was observed for the x = 0.5 magnetic annealed sample, which can be explained with magnetic atoms pair ordering theory. And the best high-temperature magnetic softness was obtained for x = 0.35 magnetic annealed sample, in which the lower λs and larger Vcry were observed.
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75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Gh Other heat and thermomechanical treatments
75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetoimpedance studies in as quenched Fe73.5Si13.5B8CuV3−xAlNbx nanocrystalline ribbons

Venkatrao Chunchu and Markandeyulu G

J. Appl. Phys. 113, 17A321 (2013); http://dx.doi.org/10.1063/1.4795800 (3 pages)

Online Publication Date: 21 March 2013

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Ribbons of Fe73.5Si13.5B8CuV3−xAlNbx (x = 0, 1.0, 1.5) alloys were prepared by melt-spun technique at the speed of 37 m/s. Crystalline phase derived from Fe3Si, in an amorphous matrix was observed in all the ribbons. As cast nanocrystalline ribbons were obtained by controlling cooling rates while quenching. The average crystallite sizes was calculated using the Scherrer's equation to be 44 nm, 39 nm, and 35 nm in x = 0, x = 1.0, and x = 1.5 ribbons, respectively. Magnetoimpedance measurements were carried out using an LCR meter. Among the investigated samples (x = 0, 1.0, 1.5), the largest magnetoimpedance of 61% was obtained for x = 1 ribbon annealed at 100 °C for 15 min, at 4 MHz.
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81.16.-c Methods of micro- and nanofabrication and processing
81.40.Gh Other heat and thermomechanical treatments
75.75.-c Magnetic properties of nanostructures
75.75.Cd Fabrication of magnetic nanostructures
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Classical eddy current losses in soft magnetic composites

C. Appino, O. de la Barrière, F. Fiorillo, M. LoBue, F. Mazaleyrat, and C. Ragusa

J. Appl. Phys. 113, 17A322 (2013); http://dx.doi.org/10.1063/1.4795744 (3 pages)

Online Publication Date: 22 March 2013

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This paper deals with the problem of loss evaluation in Soft Magnetic Composites (SMCs), focusing on the classical loss component. It is known that eddy currents can flow in these granular materials at two different scales, that of the single particle (microscopic eddy currents) and that of the specimen cross-section (macroscopic eddy currents), the latter ensuing from imperfect insulation between particles. It is often argued that this macroscopic loss component can be calculated considering an equivalent homogeneous material of same bulk resistivity. This assumption has not found so far clear and general experimental validation. In this paper, we discuss energy loss experiments in two different SMC materials, obtained using different binder types, and we verify that a classical macroscopic loss component, the sole size-dependent term, can be separately identified. It is also put in evidence that, depending on the material, the measured sample resistivity and the equivalent resistivity entering the calculation of the macroscopic eddy currents may not be the same. A corrective coefficient is, therefore, introduced and experimentally identified. This coefficient appears to depend on the material type only. An efficient way to calculate the macroscopic classical loss in these materials is thus provided.
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75.60.-d Domain effects, magnetization curves, and hysteresis
73.61.Le Other inorganic semiconductors
75.50.-y Studies of specific magnetic materials

Enhanced giant magneto-impedance effect in soft ferromagnetic amorphous ribbons with pulsed laser deposition of cobalt ferrite

A. Ruiz, D. Mukherjee, J. Devkota, M. Hordagoda, S. Witanachchi, P. Mukherjee, H. Srikanth, and M. H. Phan

J. Appl. Phys. 113, 17A323 (2013); http://dx.doi.org/10.1063/1.4795802 (3 pages)

Online Publication Date: 22 March 2013

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We have grown a 50 nm thick magnetic layer of cobalt ferrite (CFO) on two Co-based amorphous ribbons of compositions Co65Fe4Ni2Si15B14 (type I) and Co69Fe4Ni1Mo2B12Si12 (type II) by a pulsed laser deposition technique. A comparative study of the influence of this CFO layer on the giant magneto-impedance (GMI) effect and field sensitivity (η) of the ribbons is presented. Our results reveal that the presence of the CFO layer enhanced both the GMI ratio and the field sensitivity of the ribbons. Relative to the plain ribbons, the GMI ratio and field sensitivity of the CFO-coated ribbons increased by 97% and 42% for type I and by 34% and 50% for type II, respectively. The enhanced effects are attributed to the modifications on the ribbon surface and closure of magnetic flux paths due to the CFO layer.
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75.47.De Giant magnetoresistance
75.50.Kj Amorphous and quasicrystalline magnetic materials

A medium frequency transformer with multiple secondary windings for medium voltage converter based wind turbine power generating systems

Md Rabiul Islam, Youguang Guo, and Jianguo Zhu

J. Appl. Phys. 113, 17A324 (2013); http://dx.doi.org/10.1063/1.4795850 (3 pages)

Online Publication Date: 22 March 2013

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Recent advances in magnetic materials have led to the development of compact and light weight, medium and high frequency transformers, which would be a possible solution to reducing the size and weight of wind turbine power generating systems. This paper presents the overall design and analysis of a Metglas amorphous alloy 2605SA1 based medium frequency transformer to generate the isolated balanced multiple DC supplies for medium voltage converter systems. A comprehensive electromagnetic analysis is conducted on the proposed design based on experimental results. The test stand, data analysis, and test results are discussed.
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88.50.J- Wind farms
88.50.G- Wind turbines
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
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