Enhanced soft magnetic properties in magnetic field annealed amorphous Fe(Co)-Zr-B alloys
Debabrata Mishra, P. Saravanan, A. Perumal, and A. Srinivasan

Reported here are the effects of longitudinal magnetic field annealing (MFA) on the microstructure, magnetic domain structure, and magnetic softness of Co substituted amorphous Fe_89−x−yCo_yB_xZr₁₁ alloys. The observed enhancement in magnetic softness is correlated with the microstructure and magnetic domain structure.

J. Appl. Phys. 109, 07A306 (2011)

Soft magnetic properties of (Ni₈₀Fe₂₀)_1-x(Ni_0.5Zn_0.5Fe₂O₄)_x films for high frequency applications
Guangduo Lu, Huai-wu Zhang, John Q. Xiao, Xiaoli Tang, Yunsong Xie, and Zhiyong Zhong

Optimal films with the desired properties of low coercivity H_c~4 Oe, high saturation magnetization 4πMs~14.5 kG, and high electrical resistivity ρ~1500 μΩcm were obtained. The tested results shown that the sputtering power had an important effect on the films properties and that it can be convenient to adjust the natural ferromagnetic resonant frequency of the films.

J. Appl. Phys. 109, 07A308 (2011)

Stress tunable properties of ferromagnetic microwires and their multifunctional composites
F. X. Qin, H. X. Peng, V. V. Popov, L. V. Panina, M. Ipatov, V. Zhukova, A. Zhukov, and J. Gonzalez

Results for a systematic study on stress tunable absorption of glass-coated amorphous Co_68.7Fe₄Ni₁B₁₃Si₁₁Mo_2.3 microwires and their composites are presented. All these results indicate that the present composites are very promising for detecting the ambient stress levels and interrogating the structural integrity.

J. Appl. Phys. 109, 07A310 (2011)

Fe-based nanocrystalline FeBCCu soft magnetic alloys with high magnetic flux density
Xingdu Fan, Aibin Ma, He Men, Guoqiang Xie, Baolong Shen, Akihiro Makino, and Akihisa Inoue

It is found that in the Fe_84-xB₁₀C₆Cu_x alloy system, the coercivity decreases with increasing x and exhibits a minimum at around x=1.0. When x=1.0, the alloy exhibits excellent magnetic properties after the appropriate heat treatment with a high B_s of 1.78 T, low H_c of 5.1 A/m, and low core loss less than 4.3 W/kg at 1.0 T and 400 Hz that is about 55% of that of oriented Si-steel. These results indicate that the application of this alloy to power transformers will produce very large energy savings.

J. Appl. Phys. 109, 07A314 (2011)

Sub-100 μm scale on-chip inductors with CoZrTa for GHz applications
Wei Xu, Hao Wu, Donald S. Gardner, Saurabh Sinha, Tawab Dastagir, Bertan Bakkaloglu, Yu Cao, and Hongbin Yu

The inductors use copper metallization and amorphous CoZrTa thinfilms. Enhancements of 3.5X in inductance and 3X for the quality factor at frequencies as highas 3 GHz have been successfully demonstrated by using a continuous CoZrTa-ring structure in spiral inductors at the 100 μm scale. This work demonstrates significantly larger increases in inductance and quality factor atabove 1 GHz as compared to prior efforts, thereby making the added processing cost worthwhile.

J. Appl. Phys. 109, 07A316 (2011)

Reducing audible noise for distribution transformer with HB1 amorphous core
Yeong-Hwa Chang, Chang-Hung Hsu, Hung-Wei Lin, and Ching-Pei Tseng

The way to reduce the audible noise of a distribution transformer is presented by incorporating a newly developed transformer core and a rigid-structure tank. The vibrations related to the core structure and tank frame are considered, so that a distribution transformer with accelerometers mounted on the internal core and external tank, respectively, is addressed. Experimental results demonstrate that the HB1 amorphous-cored transformer with the proposed core joint and rigid-structure tank can be performed well in the aspect of audible noise reduction.

J. Appl. Phys. 109, 07A318 (2011)

First-principles investigations of Zn (Cd) doping effects on the electronic structure and magnetic properties of CoFe₂O₄
Y. H. Hou, Y. J. Zhao, Z. W. Liu, H. Y. Yu, X. C. Zhong, W. Q. Qiu, D. C. Zeng, and L. S. Wen

The optimized structures show that with increasing Zn (Cd) content the crystal lattice parameter increases by 1.47% (5.13%) when the Co ions are completely replaced by Zn (Cd) ions. The results indicate that the magnetic moment of Co/Fe ion increases and the total spin magnetic moment linearly increases with the Zn (Cd) doping from 3.00 μ_B for x=0.0 up to 10.00 μ_B for x=1.0 per formula unit.

J. Appl. Phys. 109, 07A502 (2011)

Coercivity enhancement of Dy-coated Nd-Fe-B flakes by crystallization
H. Fukunaga, Y. Sugimoto, M. Nakano, T. Yanai, S. Ohta, M. Itakura, and M. Nishida

Amorphous Nd-Fe-B flakes coated with a Dy layer were crystallized. Their coercivity H_c was enhanced by diffusion of Dy from their surfaces during crystallization. SEM and EDS analyses confirmed that Dy diffuses into the flakes. This investigation used a much lower annealing temperature (932 K) and a much shorter annealing time than those employed for diffusing Dy in sintered magnets. This enabled us to obtain isotropic Nd-Fe-B-based flakes consisting of fine grains with a high H_c.

J. Appl. Phys. 109, 07A701 (2011)

Comparative study of the magnetic properties of positive and nearly zero magnetostrictive submicron amorphous wires
Horia Chiriac, Mihaela Lostun, Gabriel Ababei, and Tibor-Adrian Óvári

Submicron wires with metallic nucleus diameters between 350 and 800 nm were investigated with hysteresis loop measurements, the magneto-optical Kerr effect, and ferromagnetic resonance studies. The analysis of the results shows the dominant role of shape anisotropy in nearly zero magnetostrictive submicron wires, as well as in positive magnetostrictive ones with nucleus diameters smaller than 350 nm.

J. Appl. Phys. 109, 07B501 (2011)

Three-dimensional Magnetic Properties of Soft Magnetic Composite Material at Different Frequencies
Yongjian Li, Zhi Wei Lin, Hongxun Liu, Yi Wang, Youguang Guo, Jianguo Zhu, and Qingxin Yang

This paper studies the 3-D magnetic properties of SMC materials under complicated magnetizations, such as circular, elliptical, and spherical excitations. The magnetic flux density vector B loci, magnetic field strength vector H loci, and core losses at magnetization frequencies ranging from 50–1000 Hz were measured and discussed using an improved 3-D testing system. Experimental results show that rotational core losses are greater than alternating losses at the same magnitude of flux density.

J. Appl. Phys. 109, 07B503 (2011)

Magnetization process and domain structure in the near-surface region of conventional amorphous wires
Horia Chiriac, Mihaela Lostun, and Tibor-Adrian Óvári

Domain imaging confirms the presence of a bamboo-type structure in the near-surface region of these materials. Surface Kerr loops show that the overall magnetization in the near-surface region has a large axial component, besides the circular one. A bistable magnetic behavior on the axial direction has been emphasized. A circularly applied field leads to the disappearance of axial magnetic bistability.

J. Appl. Phys. 109, 07B504 (2011)

High frequency characteristics of FeCoAlO thin films combined the effects of stress and magnetic field
Fu Zheng, Xuan Wang, Xu Li, Jianmin Bai, Dan Wei, Xiaoxi Liu, Wenhui Xie, and Fulin Wei

Two different configurations of the sputtering targets were used: the Al₂O₃ chips were placed on Fe₇0Co₃₀ disk either uniformly dispersed on the sputtering area (Target-A) or dispersed on the half side of the sputtering area (Target-B). It was found that, although the films deposited from both of Target A and B possessed good soft magnetic properties and in-plane uniaxial magnetic anisotropy, they showed different behaviors at high frequency.

J. Appl. Phys. 109, 07B509 (2011)

The feasibility of bit-patterned recording at 4 Tb/in.² without heat-assist
Simon John Greaves, Hiroaki Muraoka, and Yasushi Kanai

Head field distributions of shielded, single pole write heads with various main pole widths were used for recording. Write windows, showing the range of head positions which resulted in error-free recording and no adjacent track erasure, were calculated. The bit aspect ratio (BAR) and magnetic spacing between the write head and the medium were varied and the system with the lowest write error rate was found to be a 1:1 BAR, shingled recording system.

J. Appl. Phys. 109, 07B702 (2011)

Anisotropy Measurements of FePt Thin Films
H. J. Richter, O. Hellwig, S. Florez, C. Brombacher, and M. Albrecht

It is shown that the anisotropy increases with increasing chemical ordering. Within measurement accuracy, the second-order anisotropy constant K₁ is negligibly small compared to the first-order anisotropy constant K₂. The presence of a small hard-axis hysteresis causes spatial fluctuations of the field direction within the sample, which changes the shape of the hard-axis loop, such that it is misinterpreted as a K₂ in the Sucksmith–Thompson formalism.

J. Appl. Phys. 109, 07B713 (2011)

Magnetic anisotropy in (Ga,Mn)As grown on vicinal GaAs: effects of the orientation of microwave magnetic field
K. Dziatkowski, X. Liu, J. K. Furdyna, and A. Twardowski

The data collected in the growth plane reveal very limited dependence on the miscut angle η, with a negligible effect of η on the in-plane uniaxial anisotropy. In the out-of-plane configuration, the substrate misorientation has a pronounced influence on FMR, which features are partially explained with a phenomenological treatment of the atomic step-induced anisotropy.

J. Appl. Phys. 109, 07C301 (2011)

Reducing Schottky barrier height for Fe/n-GaAs junction by inserting thin GaO_x layer
H. Saito, Y. Mineno, S. Yuasa, and K. Ando

The effect of thin GaO_x insertion layers on the Schottky barrier height φ_B for Fe/n-GaAs junctions was investigated. Large suppression of φ_B is of greater advantage than using other oxide materials for achieving low contact resistance of the emitter/detector electrodes, which is the key to developing high-performance GaAs-based spintronics devices.

J. Appl. Phys. 109, 07C701 (2011)

Inversion of spin dependent photocurrent at Fe₃O₄/modulation doped GaAs heterointerfaces
Y. Shirahata, E. Wada, M. Itoh, and T. Taniyama

The spin dependent photocurrent for fully epitaxial Fe₃O₄/GaAs and Fe/GaAs interfaces clearly show the opposite magnetic field dependence, where the spin filtering efficiency for the Fe₃O₄/GaAs decreases with increasing magnetic field. The results indicate that the spin polarization of the Fe₃O₄ layer has the opposite sign to that of Fe at the Fermi energy, consistent with theoretical predictions.

J. Appl. Phys. 109, 07E105 (2011)

f-electron dependence of the physical properties of REAlB₄; an AlB₂-type analogous "tiling" compound
T. Mori, K. Kudou, T. Shishido, and S. Okada

α-HoAlB₄ and α-ErAlB₄ were synthesized, and their magnetic properties and specific heat investigated in comparison with other known rare-earth analogs. The magnetic field dependence of the irreversibility was consistent with the de Almeida Thouless (AT) line versus the quadratic suppression typically observed for antiferromagnetic systems. The specific heat exhibited behavior indicative of a multilevel Schottky anomaly and four states of the ⁵I₈ Hund’s rule multiplet of Ho³⁺ are indicated to lie below 20 K.

J. Appl. Phys. 109, 07E111 (2011)

Defect evolution during annealing of deformed FeSi alloys studied by positron annihilation spectroscopy
K. M. Mostafa, F. González Cámara, Roumen Petrov, P. Rodríguez Calvillo, E. De Grave, D. Segers, and Y. Houbaert

Optical microscopy (OM) is used to investigate the microstructure of deformed samples before and after annealing. The microstructures of the alloys, investigated by OM, show that recrystallization is completed at 900°C and the samples are mainly free of defects, which is in agreement with the positron annihilation lifetime data.

J. Appl. Phys. 109, 07E303 (2011)

A sensor measuring the Fourier coefficients of the magnetic flux density for pipe crack detection using the magnetic flux leakage method
T. Nara, Y. Takanashi, and M. Mizuide

It is shown that the crack position can be determined by the Fourier coefficients of the leakage magnetic flux density on a circle inside the pipe in the pipe cross-sectional plane. Coils that directly output the Fourier cosine and sine coefficients were made. The experimental results showed that, using only these two coils rather than dozens of magnetic sensors, the center position of a crack on the inside/outside surface of the pipe could be localized.

J. Appl. Phys. 109, 07E305 (2011)

A measurement setup for acquiring the local magnetic properties of plastically deformed soft magnetic materials
Shasha Bi, Alexander Sutor, Reinhard Lerch, and Yunshi Xiao

With the help of finite element method simulations, modifications are made on the previous double-C-yoke method to introduce a new measurement setup for extraction of the local magnetic properties.

J. Appl. Phys. 109, 07E306 (2011)

Spatial light phase modulators with one-dimensional magnetophotonic crystals driven by piezoelectric films
S. Mito, H. Takagi, P. B. Lim, A. V. Baryshev, and M. Inoue

With the application of a constant magnetic bias field perpendicular to the film plane, the magneto-optic Kerr rotation angle of the modulator was subject to continuous change from 3.8–2.4° with the voltage up to 50 V and hence a continuous phase modulation for rays with circular polarization. Surprisingly, the magneto-optical response of the modulator showed nonvolatile behavior and the light phase was maintained at a designated value without applying any stress.

J. Appl. Phys. 109, 07E313 (2011)

Enhanced resolution in magnetic force microscropy using tips with perpendicular magnetic anisotropy
S. N. Piramanayagam, M. Ranjbar, E. L. Tan, H. K. Tan, R. Sbiaa, and T. C. Chong

Here it is demonstrated that a tip coated with a magnetic film possessing a perpendicular magnetic anisotropy (PMA) offers superior resolution compared to tips without PMA. The advantages of a tip with PMA have been demonstrated based on writing magnetic transitions in a commercial perpendicular media. Magnetic force microscopy images and line scans at different scan heights are presented along with an explanation for the observed improvement in performance.

J. Appl. Phys. 109, 07E326 (2011)

Development of micro magnetostrictive wireless controllable actuator
Heung-Shik Lee, Chongdu Cho, Alan T. Zehnder, and Kyu-won Choi

The suggested worm actuator is partially coated with NiFe film of 10 μm thickness. For assaying the movement of the actuator, the curvatures of each section under the applied external magnetic field are measured using a microscope measurement system with electromagnet set. The results show wave shape movement and maximum contractile distance between the end tips of legs is 0.777 mm.

J. Appl. Phys. 109, 07E501 (2011)

Fabrication and testing of a microelectromechanical systems type dielectric core Ethernet transformer
D. Bowen, C. Krafft, and I. Mayergoyz

Toroidal 32- and 64-turn transformers with a unity turn ratio and a silicon dioxide core material were fabricated and tested. The resulting differential mode transfer relation is analyzed with infinite and 100 Ω resistive loads. The best performance is found for a 32-turn transformer with a 100 Ω load, having a relatively flat transfer relation in the frequency range of 10–40 MHz.

J. Appl. Phys. 109, 07E503 (2011)

Closed core inductor and high-K dielectric capacitor fabrication through evaporation driven nanoparticle assembly in capillaries
Sarah S. Bedair, Christopher D. Meyer, and Brian Morgan

Outlined here is a low-cost multimaterial, integrated passives approach involving suspension wicking of high-K dielectric and ferromagnetic nanoparticles into capillaries comprising inductor and capacitor passive devices. This approach has demonstrated inductance improvements of 45% up to 500 MHz with roll-off in quality factor past 225 MHz after wicking of a NiFe₂O₄ nanoparticle core.

J. Appl. Phys. 109, 07E702 (2011)

Analysis of eddy currents in magnetically nonlinear conductors
I. Mayergoyz, C. Serpico, and P. McAvoy

Analysis of eddy currents in magnetically nonlinear conductors is presented for the case of elliptical polarizations of magnetic field. Elliptical polarizations are treated as perturbations of circular polarization. The perturbation technique is developed in the reference frame rotating in synchronism with the circularly polarized solution and simple analytical solutions are found.

J. Appl. Phys. 109, 07E703 (2011)

Alignment effect between a magnet over a superconductor cylinder in the Meissner state
Ignacio Valiente-Blanco, Efren Diez-Jimenez, and Jose-Luis Perez-Diaz

Measurements are compared with values predicted by a proposed local model. Agreement between predicted values and experimental values demonstrates that the model is useful for calculating torques in addition to forces. The angle of equilibrium varies along the path over the superconducting cylinder. Therefore, shape and size determine the angle of equilibrium of the magnet.

J. Appl. Phys. 109, 07E704 (2011)

Testing and analysis of common mode characteristics of Ethernet transformers
D. Bowen, C. Krafft, and I. Mayergoyz

The testing of the common mode transfer characteristics of Ethernet transformers with (and without) inductive chokes is presented. The experimental results are compared with analytical models of common mode transfer functions of Ethernet transformers. The theory and experiment data are found to be in good agreement.

J. Appl. Phys. 109, 07E705 (2011)