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15 Aug 2002

Volume 92, Issue 4, pp. 1727-2219

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Magnetic and structural characterization of Mn-implanted, single-crystal ZnGeSiN2

S. J. Pearton, M. E. Overberg, C. R. Abernathy, N. A. Theodoropoulou, A. F. Hebard, S. N. G. Chu, A. Osinsky, V. Fuflyigin, L. D. Zhu, A. Y. Polyakov, and R. G. Wilson

J. Appl. Phys. 92, 2047 (2002); http://dx.doi.org/10.1063/1.1490621 (5 pages) | Cited 21 times

Online Publication Date: 30 July 2002

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Epitaxial layers of ZnSiN2, ZnGe0.65Si0.35N2, and ZnGe0.31Si0.69N2 grown on Al2O3 substrates were implanted at 350 °C with high doses (5×1016 cm−2) of Mn+ ions and annealed at 700 °C. The implanted region did not appear to become amorphous and showed strong selected area diffraction patterns. Hysteresis was observed in magnetization versus field curves from all of the implanted samples. Differences in field-cooled and zero field-cooled magnetization persisted to temperatures of ∼200 K for ZnSiN2, and ∼280 K for both ZnGe0.31Si0.69N2 and ZnGe0.69Si0.31N2. The results are consistent with recent magnetic data from (ZnxMn1−x)GeP2, ZnSnAs2 and (CdxMn1−x)GeP2 and suggest that this class of materials may be promising for dilute magnetic semiconductor applications. © 2002 American Institute of Physics.
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61.72.up Other materials
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Cc Kinetics of defect formation and annealing
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
75.70.Ak Magnetic properties of monolayers and thin films

Relation between microstructures and magnetic properties upon annealing in Fe50Mn50/Ni80Fe20 films

Ming Xu, Zhengqi Lu, Tao Yang, Cuixiu Liu, Shufan Cui, Zhenhong Mai, Wuyan Lai, Quanjie Jia, and Wenli Zheng

J. Appl. Phys. 92, 2052 (2002); http://dx.doi.org/10.1063/1.1493653 (6 pages) | Cited 10 times

Online Publication Date: 30 July 2002

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The annealing-temperature-dependent change in the exchange bias and coercivity is investigated in Fe50Mn50/Ni80Fe20 films. It is interesting to note that, as the annealing temperature increases, the exchange bias first decreases, and then increases, and finally decreases for the case of annealing at the higher temperature. The coercivity will increase upon annealing at moderate temperature, but decrease upon higher-temperature annealing. We can qualitatively interpret the change of the magnetic properties with annealing temperature in connection to the microstructures by x-ray scattering technologies. The results show that both the large exchange bias field and low coercivity of Fe50Mn50/Ni80Fe20 films are dependent of not only the interfacial roughness but also the antiferromagnetic structure. © 2002 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
61.72.Cc Kinetics of defect formation and annealing

Microwave magnetoabsorption in glass-coated amorphous microwires with radii close to skin depth

S. E. Lofland, H. Garcia-Miquel, M. Vazquez, and S. M. Bhagat

J. Appl. Phys. 92, 2058 (2002); http://dx.doi.org/10.1063/1.1494847 (6 pages) | Cited 18 times

Online Publication Date: 30 July 2002

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We present the frequency dependence of microwave magnetoabsorption in glass-coated amorphous microwires of (Co100−xFex)72.5Si12.5B15. The data were taken at room temperature in the frequency range of 1–60 GHz for fields up to 15 kOe by either a cavity perturbation technique or a coaxial transmission line. The resulting spectra strongly depend upon the local microwave magnetic and electric fields. We have found that we can simulate the spectra using an analytic solution to the problem of electromagnetic scattering from a cylinder. We demonstrate that these unusual spectra can be interpreted in terms of ferromagnetic resonance and antiferromagnetic resonance. However, because the electromagnetic skin depth is comparable to the radius, the resonance and antiresonance fields do not follow the conventional equations. © 2002 American Institute of Physics.
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78.70.Gq Microwave and radio-frequency interactions
75.50.Bb Fe and its alloys
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Kj Amorphous and quasicrystalline magnetic materials

Thermal-dynamic reversal of fine magnetic grains with arbitrary anisotropy axes orientation

Xiaobin Wang, H. Neal Bertram, and Vladimir L. Safonov

J. Appl. Phys. 92, 2064 (2002); http://dx.doi.org/10.1063/1.1495093 (9 pages) | Cited 14 times

Online Publication Date: 30 July 2002

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A method is developed to analyze thermally agitated magnetization reversal in a single-domain ferromagnetic grain with a uniaxial anisotropy axis oriented at an arbitrary angle to a magnetic field. Random forces and phenomenological damping consistent with thermodynamics are introduced into the dynamic equations of the normal modes. This general approach reduces to the Landau–Lifshitz–Gilbert formalism only when the magnetic energy is isotropic about the equilibrium position. A stochastic averaging method based upon a small damping parameter is used to transform the inherent two-dimensional problem into a one-dimensional form. The mean first exit time is calculated and the results for dynamic coercivity at different angles to the magnetic field are obtained. The method is ultilized to calculate the switching field versus pulse time for planar random media with noninteracting grains. The results fit well with direct Langevin simulation over short times and with Néel–Arrhenius models at long times. A general field and temperature dependent form of the attempt frequency, f0, is derived. © 2002 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.60.Jk Magnetization reversal mechanisms

Glass-forming ability and soft magnetic properties of FeCoSiAlGaPCB amorphous alloys

J. M. Borrego, A. Conde, S. Roth, and J. Eckert

J. Appl. Phys. 92, 2073 (2002); http://dx.doi.org/10.1063/1.1494848 (6 pages) | Cited 32 times

Online Publication Date: 30 July 2002

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The glass-forming ability of (FexCoyBzCu)80Si3Al5Ga2P10 with x=5–70, y=0–63, z=5–12, and u=0–5 amorphous alloys has been analyzed in terms of the width of the supercooled liquid region, the reduced glass transition temperature, and the Vogel–Fulcher–Tammann parameters. Substitution of Fe by Co slightly decreases the glass-forming ability of the studied alloys. The value of the fragility parameter m is discussed in the frame of the general classification scheme of glass-forming liquids. The crystalline phases formed during the first crystallization step are identified. Magnetic moment at low and room temperature, Curie temperature, room temperature magnetostriction, and coercivity decrease with increasing Co content. © 2002 American Institute of Physics.
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75.50.Bb Fe and its alloys
81.05.Kf Glasses (including metallic glasses)
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
64.70.K- Solid-solid transitions
75.30.Cr Saturation moments and magnetic susceptibilities
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Structural and magnetic transformation of monodispersed iron oxide particles in a reducing atmosphere

L. C. Varanda, M. Jafelicci, P. Tartaj, K. O’ Grady, T. González-Carreño, M. P. Morales, T. Muñoz, and C. J. Serna

J. Appl. Phys. 92, 2079 (2002); http://dx.doi.org/10.1063/1.1496124 (7 pages) | Cited 25 times

Online Publication Date: 30 July 2002

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Uniform metal iron ellipsoidal particles of around 200 nm in length were obtained by reduction and passivation of alumina-coated α–Fe2O3 (hematite) particles under different conditions of temperature and hydrogen flow rate. The monodispersed hematite particles were prepared by the controlled hydrolysis of ferric sulfate and further coated with a homogeneous thin layer of Al2O3 by careful selection of the experimental conditions, mainly pH and aluminum salt concentration. The reduction mechanism of α–Fe2O3 into α–Fe was followed by x-ray and electron diffraction, and also by the measurements of the irreversible magnetic susceptibility. The transformation was found to be topotactic with the [001] direction of hematite particles, which lies along the long axis of the particles, becoming the [111] direction of magnetite and finally the [111] direction of metal iron. Temperature and hydrogen flow rate during the reduction have been found to be important parameters, which determine not only the degree of reduction but also the crystallite size of the final particles. Magnetic characterization of the samples shows that the only parameters affected by the crystallite size are the saturation magnetization and magnetic time-dependence effect, i.e., activation volume. © 2002 American Institute of Physics.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Bx Metals, semimetals, and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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