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7 May 2013

Volume 113, Issue 17, Articles (17xxxx)

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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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back to top Biomedical and Molecular Magnets

Low-loss NiCuZn ferrite with matching permeability and permittivity by two-step sintering process

Hua Su, Xiaoli Tang, Huaiwu Zhang, Yulan Jing, Feiming Bai, and Zhiyong Zhong

J. Appl. Phys. 113, 17B301 (2013); http://dx.doi.org/10.1063/1.4793508 (3 pages)

Online Publication Date: 22 February 2013

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Magneto-dielectric materials with matched permeability and permittivity are promising candidates as loading materials to reduce the physical dimensions of low-frequency antennas. In this study, NiCuZn ferrites were prepared by both the traditional final-stage sintering process and the two-step sintering process to obtain the magneto-dielectric materials. It was found that the samples sintered by the two-step sintering process tended to obtain microstructure with dense, homogeneous, and small average grain size, which was favorable to obtain low magnetic and dielectric losses. The sample sintered by the two-step sintering process with high temperature 950 °C and holding temperature 900 °C could obtain almost equal permeability and permittivity of around 11.8. And the magnetic and dielectric loss tangents were lower than 0.015 in a frequency range from 10 to 100 MHz. These properties make the material useful to the design of miniaturized antennas.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics

A first-principles study of magnetism of lithium fluorosulphate LiFeSO4F

Tumurbaatar Tsevelmaa, Dorj Odkhuu, Oryong Kwon, and Soon Cheol Hong

J. Appl. Phys. 113, 17B302 (2013); http://dx.doi.org/10.1063/1.4794723 (3 pages)

Online Publication Date: 18 March 2013

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Magnetism of tavorite and triplite LixFeSO4F (x = 0, 1/2, and 1) has been studied using the first-principles density-functional theory. It was found that an antiferromagnetic ordering is more stable compared to a ferromagnetic state and the energy difference between two magnetic states is reduced when the lithium is intercalated, being consistent with a recent experimental observation of lowering Neel temperature from 100 K of FeSO4F to 25 K of LiFeSO4F. Furthermore, the magnetic moment of 3.8 μB/Fe for FeSO4F was found to be oriented along the [010], whereas that (4.3 μB/Fe) of LiFeSO4F along the [001]. And the magnetic moment and magneto-crystalline anisotropy were found to be insensitive upon different atomic structures, which imply that the lithium intercalation affects the spin orientation of Fe rather than the interplay between lattice and magnetism suggested by an experiment.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics

The low-frequency alternative-current magnetic susceptibility and electrical properties of Si(100)/Fe40Pd40B20(X Å)/ZnO(500 Å) and Si(100)/ZnO(500 Å)/Fe40Pd40B20(Y Å) systems

Yuan-Tsung Chen, S. M. Xie, and H. Y. Jheng

J. Appl. Phys. 113, 17B303 (2013); http://dx.doi.org/10.1063/1.4794985 (3 pages) | Cited 1 time

Online Publication Date: 19 March 2013

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The two deposition conditions are (a) Si(100)/Fe40Pd40B20(X Å)/ZnO (500 Å) and (b) Si(100)/ZnO(500 Å)/Fe40Pd40B20(Y Å), where X and Y are 25 Å, 50 Å, 75 Å, and 100 Å. The sputtering sequence and the thickness of the FePdB film were varied to examine their effects on the low-frequency alternative-current magnetic susceptibility (χac), maximum phase angle (θmax), maximum χac with corresponding optimal resonance frequency (fres), and electrical resistivity (ρ). Experimental results show that ZnO(500 Å)/Fe40Pd40B20(Y Å) is superior to Fe40Pd40B20(X Å)/ZnO(500 Å) because the ZnO(002) texture at the bottom can improve the magneto nanocrystalline anisotropy of Fe40Pd40B20, improving its magnetic properties. In particular, a comparison of high-resolution cross-sectional transmission electron microscopy observations of Fe40Pd40B20(100 Å)/ZnO(500 Å) and ZnO(500 Å)/Fe40Pd40B20(100 Å) demonstrates that the ZnO(002) texture induces a magneto nanocrystalline anisotropy in the nanocrystalline FePdB layer of ZnO(500 Å)/Fe40Pd40B20(100 Å), yielding a highest χac of approximately 2.8 with an fres of 1000 Hz and an θmax of 169°. Additionally, the ρ is reduced as the FePdB thickness increases, because grain boundaries and the surface of thin films scatter the electrons, so thinner films have a greater resistance. The ρ of ZnO(500 Å)/Fe40Pd40B20(Y Å) is lower than that of Fe40Pd40B20(X Å)/ZnO(500 Å) because stronger ZnO crystallization and nanocrystalline FePdB improve the scattering of electrons by the surface of the films.
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75.70.Ak Magnetic properties of monolayers and thin films
73.40.Vz Semiconductor-metal-semiconductor structures
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Kj Amorphous and quasicrystalline magnetic materials

Magnetic antibubbles: Formation and control of magnetic macroemulsions for fluid transport applications

Justin E. Silpe and David W. McGrail

J. Appl. Phys. 113, 17B304 (2013); http://dx.doi.org/10.1063/1.4796147 (3 pages)

Online Publication Date: 22 March 2013

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We report the first instance of so called magnetic antibubbles wherein the internal phase comprises an aqueous dispersion of iron oxide (Fe3O4) microparticles, and is thus capable of external control in the presence of a magnetic field. Formation of these bubbles is performed by jetting an iron oxide dispersed phase, through a gaseous medium, into a surrounding aqueous phase. At appropriate trajectory and flow rate conditions, a gas layer is entrained between the two liquids, encapsulating the internal, iron oxide core from the surrounding aqueous phase. We demonstrate that the application of a nonuniform magnetic field confers maneuverability to these bubbles, the intensity of which determines whether the Fe3O4 particles move with the antibubble intact or accelerate through the air layer causing its collapse. An externally applied magnetic field proves a sensitive and determinative means of control, and thus we believe that the magnetic antibubble represents a unique candidate for various fluid delivery and transport applications.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
47.57.Bc Foams and emulsions
82.70.Kj Emulsions and suspensions
75.50.Tt Fine-particle systems; nanocrystalline materials

Crystallographically textured self-biased W-type hexaferrites for X-band microwave applications

Zhijuan Su, Yajie Chen, Bolin Hu, Alexander S. Sokolov, Steven Bennett, Lee Burns, Xing Xing, and Vincent G. Harris

J. Appl. Phys. 113, 17B305 (2013); http://dx.doi.org/10.1063/1.4795730 (3 pages)

Online Publication Date: 29 March 2013

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We report the magnetic and structural properties of a series of W-type barium hexaferrites of composition BaZn2−xCoxFe16O27, where x = 0.15, 0.20, and 0.25. The anisotropy field of these barium ferrites (BaW) decreased with the substitution of divalent Co ions, while they maintained crystallographic c-axis texture. The measured anisotropy field was ∼10 kOe, and a hysteresis loop squareness Mr/Ms = 79% was obtained due to well-controlled grain size within the range of single domain scale. These two properties make the BaW suitable for applications in microwave devices at lower frequencies, such as self-biased circulators operated at X-band frequencies.
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61.66.Fn Inorganic compounds
61.72.-y Defects and impurities in crystals; microstructure
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Magnetic and self-biased properties of highly oriented M-type barium ferrite films on Pt-coated Si substrate by magnetron sputtering

Yuanxun Li, Yingli Liu, Jie Li, Kai Yang, and Huaiwu Zhang

J. Appl. Phys. 113, 17B306 (2013); http://dx.doi.org/10.1063/1.4798608 (3 pages)

Online Publication Date: 1 April 2013

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Highly oriented M-type barium ferrite (BaM) thin films were deposited by sputtering on Pt-coated Si Substrate with different substrate temperatures. X-ray diffraction and atomic force microscopy results show that BaM films have crystal texture of c-axis grains perpendicular to film plane with apparent hexagonal morphology. On the other hand, it is clearly observed that the remanent magnetization (Mr) in out-plane is higher than those in in-plane, and the Mr in out-plane increases with increasing the substrate temperature, reaching maximum when substrate temperature (Ts) is 600 °C. The hysteresis curves also indicate that the BaM thin film exhibits nice self-biased property with 4πMr of 3803.04 Gs, squareness ratio (Mr/Ms) of 0.96, and coercivity of 1767.3 Oe. These results make sure that these BaM films have potential for use in self-biasing microwave/millimeter wave magnetic devices such as circulators and isolators.
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75.70.Ak Magnetic properties of monolayers and thin films
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
75.78.-n Magnetization dynamics
75.50.Gg Ferrimagnetics
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Microwave complex permeability of Fe3O4 nanoflake composites with and without magnetic field-induced rotational orientation

Xianguo Liu, Siu Wing Or, Chung Ming Leung, and S. L. Ho

J. Appl. Phys. 113, 17B307 (2013); http://dx.doi.org/10.1063/1.4798606 (3 pages)

Online Publication Date: 4 April 2013

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Magnetite (Fe3O4) nanoflakes with widths of 100–200 nm and thicknesses of 10–80 nm were prepared by a hydrothermal synthesis method. Fe3O4 nanoflake composites with and without magnetic field-induced rotational orientation of flake planes of Fe3O4 nanoflakes in paraffin binder were fabricated using 35 wt. % Fe3O4 nanoflakes. The rotationally oriented composite showed higher permeability and resonance frequency than the nonoriented one, and its value of (μ0−1)fr reached 214.8 GHz and exceeded the Snoek's limit. Considering a uniform and a random distribution of flake planes of Fe3O4 nanoflakes in the oriented and nonoriented composites, respectively, the complex permeability of both composites was calculated using the Landau–Lifshitz–Gilbert equation and the Bruggeman's effective medium theory in the 2–18 GHz microwave frequency range.
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75.75.Cd Fabrication of magnetic nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
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