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1 May 2010

Volume 107, Issue 9, Articles (09xxxx)

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back to top Ferrites, Garnets, and Microwave Materials

Magnetic properties of the ferrimagnetic FeCr2−xMxS4 (M = In,Al)

Chin Mo Kim, Sam Jin Kim, Bae Soon Son, and Chul Sung Kim

J. Appl. Phys. 107, 09A501 (2010); http://dx.doi.org/10.1063/1.3337662 (3 pages)

Online Publication Date: 15 April 2010

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The polycrystalline samples of ferrimagnetic FeCr2−xMxS4 (M = In,Al; x = 0.1,0.3) have been studied with x-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. The crystal structure was found to be cubic spinel with Fd-3m space group. The lattice constants (a0) of the samples were linearly increased with Al and In concentration. Mössbauer spectra of FeCr2−xMxS4 (M = In,Al; x = 0.1,0.3) were obtained at various temperatures ranging from 4.2 to 300 K. Magnetic hyperfine field and electric quadrupole interactions for FeCr2−xMxS4 (M = In,Al; x = 0.1) at 4.2 K have been fitted, yielding the following results: for M = Al, Hhf = 139 kOe, ΔEQ = 2.54 mm/s, θ = 30°, φ = 0.0°, η = 0.9, and R = 2.7; and for M = In, Hhf = 126 kOe, ΔEQ = 2.64 mm/s, θ = 30°, φ = 0.0°, η = 1.0, and R = 3.1. The isomer shift (δ) value of the FeCr2−xMxS4 (x = 0.1) samples for both M = Al and In at 300 K was 0.50 mm/s, relative to the Fe metal, which is consistent with the Fe2+ valence state. The Debye temperatures (ΘD) of the FeCr2−xAlxS4 (x = 0.1,0.3) sample were determined to be 299±5 and 247±5 K, respectively, and those of the FeCr2−xInxS4 (x = 0.1,0.3) samples were determined to be 257±5 and 239±5 K, respectively.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Gg Ferrimagnetics
61.66.Fn Inorganic compounds
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Investigation on electromagnetic and microwave absorbing properties of La0.7Sr0.3MnO3−δ/carbon nanotube composites

C. Y. Tsay, R. B. Yang, D. S. Hung, Y. H. Hung, Y. D. Yao, and C. K. Lin

J. Appl. Phys. 107, 09A502 (2010); http://dx.doi.org/10.1063/1.3337681 (3 pages) | Cited 5 times

Online Publication Date: 15 April 2010

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In this study, the influence of the addition of carbon nanotube (CNT) (0, 0.5, 1.0, and 2.0 wt %) on complex permittivity, complex permeability, and reflection loss for La0.7Sr0.3MnO3−δ (LSMO)/polymer composites was investigated. Microwave absorbing composites were prepared by molding and curing a mixture of LSMO powders, CNTs, and epoxy resin. The complex permittivity and complex permeability for LSMO/CNT composites were examined by a cavity perturbation technique. The experimental results showed that the complex permittivity increased with increasing CNT addition and the imaginary part of the permeability decreased with rising frequency. In the present study, a microwave absorbing composite filled with 80 wt % LSOM powders and 2 wt % CNTs exhibited the optimum performance, that is, the microwave absorbing peak was −22.85 dB at 9.5 GHz and the −10 dB absorbing bandwidth reached 3.3 GHz for the sample with a matching thickness of 3 mm.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
82.35.-x Polymers: properties; reactions; polymerization
81.10.Fq Growth from melts; zone melting and refining
81.05.Qk Reinforced polymers and polymer-based composites

Relaxation behaviors of the bismuth-substituted yttrium iron garnet in the microwave range

D. S. Hung, Y. P. Fu, S. F. Lee, Y. D. Yao, and Faris B. Abdul Ahad

J. Appl. Phys. 107, 09A503 (2010); http://dx.doi.org/10.1063/1.3337682 (3 pages) | Cited 1 time

Online Publication Date: 15 April 2010

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The spin damping behavior of the bismuth-substituted yttrium iron garnets (BixY3−xFe5O12) prepared by the coprecipitation process was investigated using the ferromagnetic resonant (FMR) in this study. By analyzing the FMR responses, the spin damping coefficient of the x = 0.25–1.25 in polycrystalline Bi:YIG (yttrium aluminum garnet) samples was obtained from the 3 dB linewidth of their FMR spectra. The data demonstrated that the damping coefficient started from 3.21×10−3 for x = 0.25 and went to its minimum value of 0.31×10−3 for x = 0.75. However, the damping coefficient enhanced to 8.55×10−3 with increasing of the bismuth concentration to x = 1.25. The results revealed that the spin damping behavior of the Bi:YIG garnets was strongly dependent on a YFeO3 (111) phase.
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76.60.Es Relaxation effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Gg Ferrimagnetics

Appearance of magnetization jumps in magnetic hysteresis curves in spinel oxide FeV2O4

Sadafumi Nishihara, Wataru Doi, Hiroki Ishibashi, Yuko Hosokoshi, Xiao-Ming Ren, and Shigeo Mori

J. Appl. Phys. 107, 09A504 (2010); http://dx.doi.org/10.1063/1.3337683 (3 pages) | Cited 5 times

Online Publication Date: 15 April 2010

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We report the appearance of magnetization jumps in the magnetic hysteresis curves of the spinel oxide FeV2O4, in which two different magnetic transition ions appeared, both of them having orbital degrees of freedom. The spin-glass-like transition was observed from ac magnetic susceptibilities and the transition temperature was estimated to be Tg = 85.5 K. The magnetization jumps appear below 90 K at B = 0. In addition, jumps at B = ±1.2 T appear below 4.6 K. The magnetization jumps at B = 0 may be correlated with spin-glass-like behaviors.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Lk Spin glasses and other random magnets

Rigid and flexible Fe–Zr–N magnetic thin films for microwave absorber

Z. W. Liu (刘仲武), D. C. Zeng (曾德长), R. V. Ramanujan, and C. K. Ong

J. Appl. Phys. 107, 09A505 (2010); http://dx.doi.org/10.1063/1.3337684 (3 pages) | Cited 1 time

Online Publication Date: 15 April 2010

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FeZrN thin films with in-plane anisotropy were deposited on both rigid substrate (Si) and flexible substrate (Kapton) by magnetron sputtering. The as-prepared films had the microstructure of nanocrystallites with a small amount of intergranular amorphous phase. The thickness dependent coercivity showed different behaviors for flexible and rigid films. The dynamic magnetic properties of the films have been characterized. Although the high frequency characteristics are closely related to the thickness, composition, and anisotropy, the flexible films have relatively smaller values of real permeability μ′ but larger values of ferromagnetic resonance frequency fr than the rigid films. Due to the flexibility, the properties of the flexible films varied with each other. Nevertheless, both rigid and flexible films can find important applications in microwave absorber due to their excellent high frequency properties up to 5 GHz.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.30.Gw Magnetic anisotropy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Miniemulsion fabricated Fe3O4/poly(methyl methacrylate) composite particles and their magnetorheological characteristics

B. O. Park, K. H. Song, B. J. Park, and H. J. Choi

J. Appl. Phys. 107, 09A506 (2010); http://dx.doi.org/10.1063/1.3337686 (3 pages) | Cited 6 times

Online Publication Date: 15 April 2010

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In order to improve drawbacks such as sedimentation of magnetic particles and abrasion of the magnetorheological (MR) fluid, we have fabricated Fe3O4/poly(methyl methacrylate) (PMMA) composite particles via a double miniemulsion method and studied their MR properties. Morphology and chemical composition of the synthesized Fe3O4/PMMA composite particles were investigated by transmission electron microscopy and Fourier transform infrared, respectively. The density of the Fe3O4/PMMA composite particles was measured to be lower than that of the as-synthesized Fe3O4 particles, indicative of an improvement of the composite particles to stay dispersed. Rheological characteristics of the Fe3O4/PMMA based MR fluid dispersed in a nonmagnetic carrier fluid were measured by both static and dynamic tests using a rotational rheometer under an external magnetic field. Shear stress, yield stress, and storage modulus from the rheological measurements were obtained to be increased with applied magnetic field strengths.
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82.70.Kj Emulsions and suspensions
83.80.Gv Electro- and magnetorheological fluids
82.80.-d Chemical analysis and related physical methods of analysis
Author Select

Study on magnetic properties of low temperature sintering M-Barium hexaferrites

Yingli Liu, Yuanxun Li, Huaiwu Zhang, DaMing Chen, and Qiye Wen

J. Appl. Phys. 107, 09A507 (2010); http://dx.doi.org/10.1063/1.3338846 (3 pages) | Cited 4 times

Online Publication Date: 19 April 2010

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The effects of Zn2+ and Ti4+ substitutions on the microstructure and properties of low temperature sintered M-type barium hexaferrites Ba(ZnTi)xFe12−2xO19 have been studied in order to adapt the development of low temperature cofired ferrites technology and produce circulators with a multilayer process. It is found that part of Zn2+ ions can enter into 2b sublattice and the saturation magnetization of the samples decrease when x increases. The additive of 3–5 wt % Bi2O3⋅B2O3⋅SiO2 glass lowers the sintering temperature to about 900 °C, which is ideal for cofiring with silver paste. Scanning electron microscope and x-ray diffraction analysis show that the samples have excellent crystalline grains with a uniform size about 1.0 μm. A high density of 4.85 g/cm3 is obtained in the samples sintered at 900 °C with 5 wt % glass additive. Magnetic measurements show that the saturation magnetization reaches 63.5 emu/g (about 308 kA/m) at 900 °C and increases as the sintering temperature arises.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.72.-y Defects and impurities in crystals; microstructure
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effect of Dy-doping on the structural and magnetic properties of Co–Zn ferrite nanocrystals for magnetocaloric applications

S. Urcia-Romero, O. Perales-Pérez, and G. Gutiérrez

J. Appl. Phys. 107, 09A508 (2010); http://dx.doi.org/10.1063/1.3338847 (3 pages) | Cited 3 times

Online Publication Date: 19 April 2010

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Magnetic nanoparticles for magnetocaloric applications should combine small coercivity, low demagnetization temperature, and high pyromagnetic coefficients while keeping the magnetization as high as possible. The strong dependence of the magnetic properties of cobalt-zinc mixed ferrite with specific dopant species enables this material to be considered a promising candidate for magnetocaloric applications. On this basis, pure and Dy-doped Co0.7Zn0.3Fe2O4 cobalt-zinc ferrite nanocrystals have been synthesized by conventional and modified (i.e., flow rate controlled addition of reactants) coprecipitation routes. The modified approach allows the control of ferrite crystal growth at the nanoscale and hence tuning of the corresponding magnetic properties. The magnetic properties of the produced nanocrystals were determined as a function of their structure, nominal dopant concentration, and crystal size. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy analyses suggested both the actual incorporation of the dopants into the host ferrite lattice and the promoting effect on crystal size of the flow rate at which the reactants are contacted. The average crystallite size varied from 13 nm (no control of flow rate) to 28 nm when the ferrite was synthesized at 1 ml/min. Doping caused the maximum magnetization of the ferrite to decrease; this parameter dropped from 60 emu/g (nondoped ferrite) to 55 emu/g when the ferrite was doped with 0.01 at. % of Dy. The maximum magnetization of the Dy (y = 0.01) Co–Zn ferrite went up to 62 emu/g when the synthesis was carried out under flow-controlled conditions. The presence of 0.01 at. % Dy in the ferrite caused the demagnetization temperature to decrease from 350 °C (nondoped ferrite) to 320 °C. The demagnetization temperature was further decreased down to 308 °C when the ferrite powders were synthesized under flow rate controlled conditions.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.-d Domain effects, magnetization curves, and hysteresis
61.66.-f Structure of specific crystalline solids
61.72.U- Doping and impurity implantation
81.30.Mh Solid-phase precipitation
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Enhancement of radiated noise suppression on flexible magnetic thick film electromagnetic interference filters with high-frequency permeability on data signal cable

Kyung Sub Lee, In-Ho Byun, In-Bum Jeong, and Sang Woo Kim

J. Appl. Phys. 107, 09A509 (2010); http://dx.doi.org/10.1063/1.3356234 (3 pages)

Online Publication Date: 22 April 2010

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Frequency-dependent impedance characteristics of flexible thick film EMI filters were investigated for enhanced suppression of high-frequency noise currents in the frequency range from several tens of megahertz to 1.5 GHz. The inductance of the rolled magnetic film filters was much lower than that of the conventional ferrite bead at lower frequencies but the inductance exceeded the level of the ferrite bead above 33–125 MHz because of the higher frequency dependence of real permeability. The enhanced impedance was mainly due to the increased inductance for the rolled thick film filters at lower frequencies of 210–550 MHz, depending on the complex permeability. The enhanced permeability at the higher frequency was attributed to the increased inductance and resistance of the rolled magnetic thick film filters. The higher frequency dependence of impedance was, the better the effect was reached to filter out the common-mode noise. It is found that the noise emission from a data signal cable is effectively suppressed by employing the flexible magnetic thick films as a common-mode noise filter in the 50 MHz–1.5 GHz frequency band.
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84.30.Vn Filters
84.40.Dc Microwave circuits
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
85.40.Xx Hybrid microelectronics; thick films
07.50.Hp Electrical noise and shielding equipment

Crystal structure and magnetic properties of rf-sputtered Cu–Zn ferrite thin films

M. Sultan and R. Singh

J. Appl. Phys. 107, 09A510 (2010); http://dx.doi.org/10.1063/1.3357316 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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Cu–Zn ferrite (Cu0.6Zn0.4Fe2O4) thin films were deposited using rf-magnetron sputtering on glass substrates at room temperature in pure Ar gas environment. The influence of variation in Ar gas pressure between 5 and 15 mT on the crystal structure and magnetization has been studied. The XRD patterns show single phase nanocrystalline spinel structure with cubic symmetry. The AFM images also confirm the nanocrystalline nature of the films. The magnetization increases with increase in Ar gas pressure. The change in the crystal structure and magnetization has been explained in view of freezing of some Cu-ions on tetrahedral A-sites and equivalent number of Fe ions on octahedral B-sites during the deposition process due to high deposition rate in pure Ar environment. Furthermore, the deposition in reducing (argon) atmosphere may lead to the formation of Cu+ ions that prefer occupation of the smaller four-coordinated A-site in the spinel structure and displace Fe3+ cations to occupy the B-sites. The formation of Fe2+ cannot be ruled out in the spinel structure where a fraction of Fe3+ will be replaced by Fe2+ ions.
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61.66.Fn Inorganic compounds
68.55.at Other materials
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Gg Ferrimagnetics
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Influence of MgTiO3 on the magnetic and dielectric properties of Ba3Co2Fe24O41 hexaferrite

C. H. Mu, Y. L. Liu, H. W. Zhang, Y. Q. Song, Q. Y. Wen, and J. Shen

J. Appl. Phys. 107, 09A511 (2010); http://dx.doi.org/10.1063/1.3338692 (3 pages) | Cited 1 time

Online Publication Date: 26 April 2010

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MgTiO3-doped Ba3Co2Fe24O41 hexaferrites (Co2Z) have been prepared by the solid-state reaction method, and the magnetic and dielectric properties have been investigated. Permeability measurements indicate that MgTiO3 doping significantly improves the frequency characteristics of permeability, i.e., with the increase of MgTiO3 doping content from 0 to 5 wt %, the cutoff frequency increases greatly from 0.33 GHz to >1.8 GHz. Although μ′ decreases from 16.1 to 5.4 in a sample doped with 5 wt % MgTiO3, magnetic loss μ″ is effectively suppressed in frequency above 300 MHz. The permittivity of 5 wt % MgTiO3 doped specimen keeps stable in the value of about 17, while the dielectric loss largely decreases in the frequency rang from 300 MHz to 1.8 GHz. The low magnetic and dielectric loss and the improvement of frequency characteristics are crucial for high-frequency antenna applications of Z-type hexaferrites.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.-d Domain effects, magnetization curves, and hysteresis
77.22.Ch Permittivity (dielectric function)
61.72.U- Doping and impurity implantation
75.50.Gg Ferrimagnetics
77.22.Gm Dielectric loss and relaxation

Structural and size dependent magnetic properties of single phase nanostructured gadolinium-iron-garnet under high magnetic field of 32 tesla

C. N. Chinnasamy, J. M. Greneche, M. Guillot, B. Latha, T. Sakai, C. Vittoria, and V. G. Harris

J. Appl. Phys. 107, 09A512 (2010); http://dx.doi.org/10.1063/1.3357326 (3 pages) | Cited 2 times

Online Publication Date: 28 April 2010

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Here we report the single phase nanostructured Gd3Fe5O12 garnets with different grain sizes (bulk, 75, 47, 35, and 22 nm) were prepared by ball milling for various milling times. Both the average grain size and the lattice parameter were estimated from the x-ray diffraction line broadening. The 57Fe Mössbauer spectra were recorded at 300 and 77 K for the samples with different grain sizes clearly evidenced the formation of Fe2+ ions induced by milling and the content of Fe2+ increases with milling time. At 4.2 K, a significant increase in saturation magnetization (+11%) has been observed for the 47 nm particles. The magnetization is strongly applied field dependent and no saturation effect is observed even at fields as high as of 320 kOe. The results presented here have been explained in terms of the key role played by the Fe2+ ions.
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61.66.Fn Inorganic compounds
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Determination of negative permeability and permittivity of metal strip coated ferrite disks using the transmission and reflection technique

N. Rahman, M. Obol, A. Sharma, and M. N. Afsar

J. Appl. Phys. 107, 09A513 (2010); http://dx.doi.org/10.1063/1.3357327 (3 pages)

Online Publication Date: 29 April 2010

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In this paper, a full band microwave isolator constructed from an array of metal wire-coated ferrite samples is presented. Here, the magnetic permeability of the metamaterialized structure is controlled by a relatively weak external magnetic field. The tunable permeability of the ferrites in this experiment allows us to create unidirectional wave propagation through the structure over the entire X-band frequency spectrum. The analysis presented here takes into account potential surface plasmon modes generated between the gaps of metal wires when the external magnetic field is applied. Here, we present a modification of the traditional transmission-reflection measurement method by normalizing the transmission and reflection coefficients. This modification removes the occurrence of atypical phenomena for negative imaginary components of permeability and permittivity that arises in the measurement of metamaterials. Our modified method precisely determines the refractive index, impedance, permittivity, and permeability of both traditional reciprocal networks as well as nonreciprocal networks, such as the one presented here.
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85.70.Ge Ferrite and garnet devices
84.40.Az Waveguides, transmission lines, striplines

Growth of highly textured manganese zinc ferrite films on glass substrates

H. Waqas, X. L. Huang, J. Ding, H. M. Fan, Y. W. Ma, T. S. Herng, A. H. Quresh, J. Q. Wei, D. S. Xue, and J. B. Yi

J. Appl. Phys. 107, 09A514 (2010); http://dx.doi.org/10.1063/1.3367964 (3 pages) | Cited 1 time

Online Publication Date: 3 May 2010

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Highly textured manganese zinc ferrite (Mn0.7Zn0.3Fe2O4) films have been successfully fabricated on glass substrates by pulse laser deposition at relatively low temperatures. Investigations indicated that the strain, which is induced by high deposition rate and the difference of thermal coefficient between the film and glass substrate, is attributed to the growth of textured structure. Growth of highly textured cobalt ferrite film was also achieved using the same method. This work provided a possible technique for fabricating high quality ferrite films on glass substrates.
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81.15.Fg Pulsed laser ablation deposition
68.55.at Other materials
68.55.jm Texture
75.50.Gg Ferrimagnetics
75.70.Ak Magnetic properties of monolayers and thin films

Numerical simulation of wave propagation in Y- and Z-type hexaferrites for high frequency applications

J. W. Wang, A. L. Geiler, V. G. Harris, and C. Vittoria

J. Appl. Phys. 107, 09A515 (2010); http://dx.doi.org/10.1063/1.3338970 (3 pages) | Cited 3 times

Online Publication Date: 4 May 2010

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The dispersion characteristics of microstrip lines on magnetically anisotropic substrates are studied utilizing the Galerkin’s method in the spectral domain. Specifically, we calculate the differential phase shifts of devices consisting of Z-type (Zn2Z) and Y-type (Zn2Y) ferrites as a function of applied magnetic field. Our theoretical formulism is effective in modeling highly magnetically anisotropic materials, which are becoming increasingly important for the next generation of microwave devices. Such a theoretical treatment of anisotropic ferrite magnetic materials is presently unavailable in commercial numerical simulation tools.
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84.40.Az Waveguides, transmission lines, striplines
75.50.Gg Ferrimagnetics
02.70.Dh Finite-element and Galerkin methods

Growth of crystalline cobalt ferrite thin films at lower temperatures using pulsed-laser deposition technique

A. Raghunathan, I. C. Nlebedim, D. C. Jiles, and J. E. Snyder

J. Appl. Phys. 107, 09A516 (2010); http://dx.doi.org/10.1063/1.3357315 (3 pages) | Cited 6 times

Online Publication Date: 4 May 2010

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Cobalt ferrite thin films were grown on SiO2/Si(100) substrates using pulsed-laser deposition technique at substrate temperatures ranging from 250 to 600 °C. Thermal expansion mismatch between the film and substrate appears to have a substantial effect on the magnetic properties of the cobalt ferrite films, due to the large magnetoelastic coupling of cobalt ferrite. It was shown in this study, that polycrystalline films with (111)-preferred orientation could be prepared at substrate temperatures as low as 250 °C. The growth of crystalline cobalt ferrite films at such low temperatures indicates the potential to use cobalt ferrite for microelectromechanical systems devices and sensor applications including integration with a wider range of multilayer device structures.
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68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
75.70.Ak Magnetic properties of monolayers and thin films
75.80.+q Magnetomechanical effects, magnetostriction
75.50.Gg Ferrimagnetics
65.40.De Thermal expansion; thermomechanical effects

Accurate modeling of voltage and current waveforms with saturation and power losses in a ferrite core via two-dimensional finite elements and a circuit simulator

R. A. Salas and J. Pleite

J. Appl. Phys. 107, 09A517 (2010); http://dx.doi.org/10.1063/1.3357313 (3 pages) | Cited 2 times

Online Publication Date: 5 May 2010

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This paper presents a new dynamic model of equivalent circuit to simulate in the time-domain the effects of saturation and power losses in a nonlinear magnetic component. The parameters of the model are a nonlinear inductance and a nonlinear loss resistance that are computed via two-dimensional finite elements. The effectiveness of the model is analyzed in the case of a soft ferrite inductor excited by a sinusoidal voltage source at frequencies of 500 Hz and 40 kHz. The resulting voltage and current waveforms of the inductor taken in the laboratory are then compared with those computed via the PSIM circuit simulator. PSIM is a simulation software designed for power electronics, motor control, and dynamic system simulation.
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84.32.Hh Inductors and coils; wiring
02.70.Dh Finite-element and Galerkin methods

Influential parameters on electromagnetic properties of nickel–zinc ferrites for antenna miniaturization

David Souriou, Jean-Luc Mattei, Alexis Chevalier, and Patrick Queffelec

J. Appl. Phys. 107, 09A518 (2010); http://dx.doi.org/10.1063/1.3356235 (3 pages) | Cited 2 times

Online Publication Date: 6 May 2010

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Electromagnetic properties of nickel–zinc ferrites based materials make them potential candidates for applications linked to telecommunications. In the present study, nanosized particles of spinel ferrite Ni0.5Zn0.3Co0.2Fe2O4 were prepared by coprecipitation method. An optimized material is obtained after adequate heat treatment and partial filling of the porosity by epoxy resin. This material lies between ceramic and composite medium (with porosity close to 40%), and shows almost constant complex permeability and permittivity in the frequency range from 0.1–0.7 GHz, and equal to ∼ 3.5-j0.15 (loss tangent ∼ 0.04) and ∼ 4-j0.2 (loss tangent ∼ 0.02), respectively. The refractive index n is close to 3.75. These electromagnetic properties, in particular the low levels of losses, show that this material could be useful to the design of miniaturized antennas in the VHF-uhf (300–700 MHz) range of frequency.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.40.Gh Other heat and thermomechanical treatments
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.50.Gg Ferrimagnetics
84.40.Ua Telecommunications: signal transmission and processing; communication satellites

Synthesis of nanocrystalline Ni–Zn ferrites by combustion method with no postannealing route

Chao-Ming Fu, Ming-Ru Syue, Fu-Jin Wei, Chao-Wen Cheng, and Chan-Shin Chou

J. Appl. Phys. 107, 09A519 (2010); http://dx.doi.org/10.1063/1.3337689 (3 pages) | Cited 3 times

Online Publication Date: 10 May 2010

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Nanocrystalline Ni–Zn ferrites were synthesized by a novel combustion route without post annealing process. The sintered ferrites characterized by X-ray diffraction have shown highly pure nanocrystalline phase. Calculated by the Scherrer’s formula, the estimated crystallite size is about 26–41 nm and lattice constant of the cubic spinel was 8.353–8.458 Å. The saturated magnetization is in the range of 6–57 emu/g and the corresponded coercivity varies from 26 to 221 Oe. Further, the high frequency electromagnetic properties were investigated by analysis of magnetoimpedance spectra. The novel combustion synthesis without post annealing has implied for practical industrial fabrication of ferrites for electromagnetic applications, inherently interest of energy efficiency and cost effective.
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81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
82.60.Cx Enthalpies of combustion, reaction, and formation
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.66.-f Structure of specific crystalline solids
75.50.Gg Ferrimagnetics

Synthesis of copper ferrite from thermolysis of copper ferrimalonate precursor (invited)

Jashanpreet Singh, Harpreet Kaur, Manpreet Kaur, and B. S. Randhawa

J. Appl. Phys. 107, 09A520 (2010); http://dx.doi.org/10.1063/1.3337688 (3 pages) | Cited 2 times

Online Publication Date: 11 May 2010

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The thermolysis of copper ferrimalonate Cu3[Fe(CH2C2O4)3]2⋅9H2O has been investigated up to 1073 K in flowing air atmosphere employing various physico-chemical techniques, i.e., simultaneous TG-DTG-DSC, XRD, Mössbauer, IR, and TEM. The precursor undergoes dehydration and decomposition simultaneously to yield copper malonate and iron(II) malonate intermediates at 433 K. At higher temperature (548 K) these intermediate species decompose to CuO and α-Fe2O3, respectively. Finally, copper ferrite, CuFe2O4, has been obtained as a result of solid state reaction between α-Fe2O3 and CuO at a temperature (623 K) much lower than that for conventional ceramic method. The TEM analysis of the final thermolysis product reveals the formation of monodisperse copper ferrite nanoparticles with an average particle size of 33 nm. Magnetic studies show that these nanoparticles exhibit saturation magnetization of 2783 G and Curie temperature of 709 K. Lower magnitude of these parameters as compared with the bulk values may be attributed to the ultrafine grain size of the ferrite particles.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.16.Be Chemical synthesis methods

Ab initio study on copper ferrite

Min Feng, Aria Yang, Xu Zuo, Carmine Vittoria, and Vincent G. Harris

J. Appl. Phys. 107, 09A521 (2010); http://dx.doi.org/10.1063/1.3338905 (3 pages)

Online Publication Date: 13 May 2010

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The impact of cation distribution on electronic structure and magnetic properties is investigated by the first-principle calculation. The structure optimization is based on generalized gradient approximation (GGA) exchange-correlation and projector augmented wave method. The optimized structures of inverse and normal copper ferrite are tetragonal (c/a = 1.06) and cubic, respectively. The optimized structure of partial inverse copper ferrites can be cubic, tetragonal, or triclinic depending on the distribution of copper ions. The calculation of electronic structure is based on full potential linear augmented plane wave method and GGA+U exchange-correlation. The calculated density of states shows that the distribution of Cu ions impacts the electronic structure significantly. The normal and inverse copper ferrite are half-metallic and semiconducting, respectively. The partial inverse copper ferrites are metallic or half-metallic.
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71.15.-m Methods of electronic structure calculations
75.50.Gg Ferrimagnetics

Temperature dependent valence states and magnetic properties of lithium delithiated Li0.59FePO4

In Kyu Lee, In-Bo Shim, and Chul Sung Kim

J. Appl. Phys. 107, 09A522 (2010); http://dx.doi.org/10.1063/1.3337680 (3 pages) | Cited 6 times

Online Publication Date: 14 May 2010

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Polycrystalline samples of Li0.59FePO4 were prepared by oxidation reaction of pure LiFePO4, and temperature dependent valence states and magnetic properties were studied. X-ray diffraction patterns showed a biphasic olivine-type orthorhombic structure (space group: Pnma) where triphylite (LiFePO4) and heterosite (FePO4) coexisted. Also, we have observed the biphasic antiferromagnetic ordering of triphylite and heterosite with different antiferromagnetic to paramagnetic ordering transition temperatures. Mössbauer spectra of Li0.59FePO4 showed a two-phase asymmetrical eight line pattern due to the different electric quadrupole interactions in triphylite and heterosite. The iron ions of triphylite and heterosite are at Fe2+ (3d6) and the Fe3+ (3d5) valence state. Also the large value of ΔEQ for the triphylite phase was originated from the asymmetric charge distribution of FeO6. These results indicate that the charge distributions around the Fe nucleus in the triphylite are more asymmetric because of the contribution from the crystal field and the ion valence state.
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71.70.Ch Crystal and ligand fields
71.70.Jp Nuclear states and interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.20.Ck Nonmetals
61.66.Fn Inorganic compounds
75.50.Ee Antiferromagnetics

Microwave absorbing properties of La0.7Sr0.3MnO3 composites with negative magnetic susceptibility

R. B. Yang, C. Y. Tsay, W. F. Liang, and C. K. Lin

J. Appl. Phys. 107, 09A523 (2010); http://dx.doi.org/10.1063/1.3337685 (3 pages) | Cited 3 times

Online Publication Date: 17 May 2010

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The complex permittivity and permeability of La0.7Sr0.3MnO3 (LSMO)-epoxy composite absorbers are investigated in the microwave ranges from 2 to 18 GHz by transmission/reflection method. A negative magnetic susceptibility of perovskite oxides has been obtained in the frequency range of 4–18 GHz. By the use of the cavity perturbation technique, the negative magnetic susceptibility for 7.5–14 GHz is reconfirmed. For LSMO-epoxy composite with 80 wt % fillers, the maximum reflection loss can reach 23 dB at 10.5 GHz and the absorbing bandwidth above 10 dB is 1.5 GHz with 2 mm thickness.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
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