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6 May 2002

Volume 80, Issue 18, pp. 3247-3450

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Effects of rapid thermal annealing on the ferromagnetic properties of sputtered Zn1−x(Co0.5Fe0.5)xO thin films

Young Mok Cho, Woong Kil Choo, Hyojin Kim, Dojin Kim, and YoungEon Ihm

Appl. Phys. Lett. 80, 3358 (2002); http://dx.doi.org/10.1063/1.1478146 (3 pages) | Cited 127 times

Online Publication Date: 29 April 2002

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We have investigated the effects of rapid thermal annealing under vacuum on the CoFe-doped ZnO [Zn1−x(Co0.5Fe0.5)xO] films grown by reactive magnetron co-sputtering. At least up to x = 0.15, the films have the single phase of the same wurtzite structure as pure ZnO. Ferromagnetism was observed for the CoFe-doped ZnO films. We found that rapid thermal annealing leads to a remarkable increase in the spontaneous magnetization of the CoFe-doped ZnO as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (TC), resulting in room temperature ferromagnetism with TC>300 K for the CoFe-doped ZnO films. © 2002 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
81.05.Dz II-VI semiconductors
81.40.Rs Electrical and magnetic properties related to treatment conditions
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
68.55.-a Thin film structure and morphology
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order

Magnetic anisotropy of ferromagnetic La0.7Sr0.3MnO3 epitaxial thin films: Dependence on temperature and film thickness

K. Steenbeck, T. Habisreuther, C. Dubourdieu, and J. P. Sénateur

Appl. Phys. Lett. 80, 3361 (2002); http://dx.doi.org/10.1063/1.1473870 (3 pages) | Cited 34 times

Online Publication Date: 29 April 2002

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The magnetic anisotropy of (001) oriented La0.7Sr0.3MnO3 films of thickness t = 7–156 nm, deposited on LaAlO3 substrates, was measured by torque magnetometry in the temperature range T = 10–300 K. For t ≥ 50 nm and H rotating out of plane the anisotropy Ku agrees well with shape anisotropy. For thinner films, Ku is reduced and its sign is reversed for t = 7 nm and T<70 K; this can be explained by a perpendicular anisotropy Kuϵ due to lattice strain. The crystal anisotropy constant K1 was determined from the biaxial in-plane anisotropy. At T = 100 K K1 differed by no more than 50% from the mean value −8 kJ/m3 in the thickness region investigated. K1 was much less dependent on the thickness t and strain relaxation in the films than Kuϵ. © 2002 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology

Room temperature operation of a high output current magnetic tunnel transistor

Sebastiaan van Dijken, Xin Jiang, and Stuart S. P. Parkin

Appl. Phys. Lett. 80, 3364 (2002); http://dx.doi.org/10.1063/1.1474610 (3 pages) | Cited 50 times

Online Publication Date: 29 April 2002

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The structure and properties of a magnetic tunnel transistor with high current output at room temperature are presented. The transistor marries a two-terminal magnetic tunnel junction with an Al2O3 tunnel barrier and a GaAs collector. The output current depends on the spin-dependent transport of hot electrons in the base layer of the transistor, which is formed from a single ultrathin ferromagnetic film. At a bias voltage of 1.4 V across the tunnel barrier, output currents larger than 1 μA and magnetocurrent changes of 64% are obtained at room temperature. © 2002 American Institute of Physics.
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85.75.Mm Spin polarized resonant tunnel junctions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Bb Fe and its alloys

Large low-field magnetoresistance of phase-separated single-crystalline Pr0.7Pb0.3MnO3

Run-Wei Li, Zhi-Hong Wang, Wei-Ning Wang, Ji-Rong Sun, Qing-An Li, Shao-Ying Zhang, Zhao-Hua Cheng, Bao-Gen Shen, and Ben-Xi Gu

Appl. Phys. Lett. 80, 3367 (2002); http://dx.doi.org/10.1063/1.1477940 (3 pages) | Cited 12 times

Online Publication Date: 29 April 2002

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A large low-field magnetoresistance (MR) slightly above the metal–insulator transition temperature (234 K) was observed in single-crystalline Pr0.7Pb0.3MnO3. Combining the temperature dependence of magnetization, resistance, and electron spin resonance spectra, it was suggested that phase separation occurs above the Curie temperature; ferromagnetic metallic clusters imbedding in the insulating paramagnetic matrix, and spin-polarized electron tunneling between isolated ferromagnetic clusters should be responsible for the large low-field MR observed. Undoubtedly, this observation opens a window to explore large low-field MR at high temperature, which is very important for the practical application of colossal MR effect. © 2002 American Institute of Physics.
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64.75.-g Phase equilibria
72.25.-b Spin polarized transport
72.60.+g Mixed conductivity and conductivity transitions
72.20.My Galvanomagnetic and other magnetotransport effects
75.47.Gk Colossal magnetoresistance
71.30.+h Metal-insulator transitions and other electronic transitions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Sk Insulators
76.30.-v Electron paramagnetic resonance and relaxation
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