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28 Jan 2008

Volume 92, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 041901 (2008); http://dx.doi.org/10.1063/1.2831926 (3 pages)

M. A. Avila, K. Suekuni, K. Umeo, H. Fukuoka, S. Yamanaka, and T. Takabatake
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Conversion from transparent antiferromagnet KNiF3 to transparent ferrimagnets

H. Manaka, Y. Watanabe, K. Kikunaga, T. Yamamoto, N. Terada, and K. Obara

Appl. Phys. Lett. 92, 042501 (2008); http://dx.doi.org/10.1063/1.2837540 (3 pages)

Online Publication Date: 28 January 2008

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We succeeded in performing a magnetic conversion from transparent antiferromagnet KNiF3 to transparent ferrimagnets, with a spontaneous ferromagnetic moment by a percolation method. Considering Coulomb repulsion, the origin of the spontaneous ferromagnetic moment is explained by an inhomogeneous antiferromagnetic spin arrangement, even if nonmagnetic ions are dispersed homogenously over KNiF3. The ferromagnetic transition temperature was obtained to be 24–26 K. The transmittance at 600–1000 nm was excellent. This compound shows an alternative that can be used for an optical isolator that uses commercial semiconductor lasers, and can widely be used in next generation optical information networks.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Gg Ferrimagnetics
75.50.Ee Antiferromagnetics

Effect of donor localization on the magnetic properties of Zn–Co–O system

Xue-Chao Liu, Er-Wei Shi, Zhi-Zhan Chen, Tao Zhang, Yong Zhang, Bo-Yuan Chen, Wei Huang, Xi Liu, Li-Xin Song, Ke-Jin Zhou, and Ming-Qi Cui

Appl. Phys. Lett. 92, 042502 (2008); http://dx.doi.org/10.1063/1.2838292 (3 pages) | Cited 10 times

Online Publication Date: 28 January 2008

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The effect of donor localization on the magnetic properties of Zn–Co–O system was investigated by resonant inelastic x-ray scattering and first principle calculations. It was found that the ferromagnetic coupling was induced through charge transfer between Co 3d and donor defect. The charge transfer was dependent on the electron localization of donor defect. The electron localization of oxygen vacancy defect was much stronger than that of donor defect formed by the substitution of Al3+ for Zn2+. In order to elucidate the magnetic mechanism, a series of Zn0.95Co0.05O and Zn0.94Co0.05Al0.01O films were prepared under different oxygen partial pressure (PO2). The magnetic properties of Zn0.95Co0.05O films were dependent on PO2, while Zn0.94Co0.05Al0.01O films showed stable ferromagnetism.
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75.50.Pp Magnetic semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
75.50.Dd Nonmetallic ferromagnetic materials

Heteroepitaxial growth of ferromagnetic rutile CoxTi1−xO2−δ on GaN (0001)

Yasushi Hirose, Taro Hitosugi, Junpei Kasai, Yutaka Furubayashi, Kiyomi Nakajima, Toyohiro Chikyow, Seiji Konuma, Toshihiro Shimada, and Tetsuya Hasegawa

Appl. Phys. Lett. 92, 042503 (2008); http://dx.doi.org/10.1063/1.2838297 (3 pages) | Cited 1 time

Online Publication Date: 28 January 2008

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A rutile CoxTi1−xO2−δ (100) film was heteroepitaxially grown on GaN (0001) by pulsed laser deposition. Magneto-optical Kerr effect and cross-sectional transmission electron microscope (TEM) measurements revealed that Co0.03Ti0.97O2−δ films prepared at an oxygen partial pressure of 10−6–10−5 Torr with a carrier density ne ≥ 3×1018 cm−3 exhibit room-temperature ferromagnetism without any precipitates or secondary phase. High-resolution TEM observations confirmed that the interface between CoxTi1−xO2−δ and GaN is atomically smooth without intermixing. These results lead us to conclude that CoxTi1−xO2−δ is promising as a spin injector in GaN-based spin-electronic devices.
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81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects

Thermal and magnetic field-induced martensite-austenite transition in Ni50.3Mn35.3Sn14.4 ribbons

B. Hernando, J. L. Sánchez Llamazares, J. D. Santos, Ll. Escoda, J. J. Suñol, R. Varga, D. Baldomir, and D. Serantes

Appl. Phys. Lett. 92, 042504 (2008); http://dx.doi.org/10.1063/1.2838356 (3 pages) | Cited 16 times

Online Publication Date: 29 January 2008

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Thermal and field-induced martensite-austenite transition was studied in melt spun Ni50.3Mn35.3Sn14.4 ribbons. Its distinct highly ordered columnarlike microstructure normal to ribbon plane allows the direct observation of critical fields at which field-induced and highly hysteretic reverse transformation starts (H = 17 kOe at 240 K), and easy magnetization direction for austenite and martensite phases with respect to the rolling direction. Single phase L21 bcc austenite with TC of 313 K transforms into a 7M orthorhombic martensite with thermal hysteresis of 21 K and transformation temperatures of MS = 226 K, Mf = 218 K, AS = 237 K, and Af = 244 K.
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81.30.Kf Martensitic transformations
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.kd Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
81.40.Gh Other heat and thermomechanical treatments

Lateral-displacement influence on the levitation force in a superconducting system with translational symmetry

Nuria Del–Valle, Alvaro Sanchez, Carles Navau, and Du-Xing Chen

Appl. Phys. Lett. 92, 042505 (2008); http://dx.doi.org/10.1063/1.2838311 (3 pages) | Cited 12 times

Online Publication Date: 30 January 2008

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The unique properties of superconductors make the design of levitation devices possible. In some of them, lateral displacements of the superconducting levitating part often result in a decrease in the levitation force, which can cause a critical malfunction of the system. In this work, the authors theoretically analyze the levitation force of a system consisting of an infinitely long superconductor over an infinitely long permanent-magnet guideway using a realistic model based on a magnetic-energy minimization procedure, from which they give the physical keys for understanding the levitation force reduction after lateral displacements and how to minimize these effects.
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84.71.Ba Superconducting magnets; magnetic levitation devices
85.70.Rp Magnetic levitation, propulsion and control devices
75.50.Ww Permanent magnets
74.25.Ha Magnetic properties including vortex structures and related phenomena

Influence of disorder on the in-field Jc of MgB2 wires using highly active pyrene

J. H. Kim, X. Xu, M. S. A. Hossain, D. Q. Shi, Y. Zhao, X. L. Wang, S. X. Dou, S. Choi, and T. Kiyoshi

Appl. Phys. Lett. 92, 042506 (2008); http://dx.doi.org/10.1063/1.2838756 (3 pages) | Cited 10 times

Online Publication Date: 31 January 2008

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In this work, we report on significantly enhanced critical current density (Jc) in MgB2 superconductor that was easily obtained by doping with a hydrocarbon, highly active pyrene (C16H10), and using a sintering temperature as low as ∼ 600 °C. The processing advantages of the C16H10 additive include production of a highly active carbon (C) source, an increased level of disorder, and the introduction of small grain size, resulting in enhancement of Jc.
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74.25.Sv Critical currents
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Analyses on double resonance behavior in microwave magnetic permeability of multiwalled carbon nanotube composites containing Ni catalyst

Fusheng Wen, Haibo Yi, Liang Qiao, Hong Zheng, Dong Zhou, and Fashen Li

Appl. Phys. Lett. 92, 042507 (2008); http://dx.doi.org/10.1063/1.2839382 (3 pages) | Cited 24 times

Online Publication Date: 31 January 2008

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The double resonance behavior of microwave magnetic permeability has been observed for multiwalled carbon nanotube composites containing Ni catalyst. One of them is due to the natural resonance at 6.00 GHz and another is due to the exchange resonance at 10.11 GHz. The natural resonance is dependent on magnetocrystalline anisotropy and shape anisotropy of Ni nanostick catalyst and the calculated result of exchange resonance mode with a few modifications was close to the experiment. It is believed that the coexistence of natural resonance and exchange resonance is benefial to large bandwidth as a microwave absorber.
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78.70.Gq Microwave and radio-frequency interactions
75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
81.07.De Nanotubes
75.75.-c Magnetic properties of nanostructures

Magnetoelectric effects in composite of nanogranular Fe/TiO2−δ films

S. D. Yoon, C. Vittoria, Y. N. Srivastava, A. Widom, and V. G. Harris

Appl. Phys. Lett. 92, 042508 (2008); http://dx.doi.org/10.1063/1.2838757 (3 pages) | Cited 4 times

Online Publication Date: 1 February 2008

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Employing a new experimental technique to measure magnetoelectric response functions, we have measured the magnetoelectric effect in composite films of nanogranular metallic iron in anatase titanium dioxide at temperatures below 50 K. A magnetoelectric resistance is defined as the ratio of a transverse voltage to bias current as a function of magnetic field. In contrast to the anomalous Hall resistance measured above 50 K, the magnetoelectric resistance below 50 K is significantly larger and exhibits an even symmetry with respect to magnetic field reversal H→−H. The composite films are unique in terms of showing magnetoelectric effects at low temperatures, <50 K, and anomalous Hall effects at high temperatures, >50 K.
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75.80.+q Magnetomechanical effects, magnetostriction
77.80.-e Ferroelectricity and antiferroelectricity
75.47.Pq Other materials
75.50.Bb Fe and its alloys
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