Browsing by Author "Liu, S. J."

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Anisotropic magnetoresistance of La0.7Ca0.3MnO3 thin film biepitaxial step junctions
(2006-12-01)
Chen, S. F.
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Chang, W. J.
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Hsieh, C. C.
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Liu, S. J.
;
Juang, J. Y.
The angular dependence of magnetoresistance (MR) of the La0.7Ca0.3MnO3 thin film biepitaxial step junction (BSJ) shows a simple sin(2)(theta) dependence in the in-plane high-field magnetoresistance, with theta being the angle between the applied field and current. This behavior is similar to the spin-orbit coupling-induced anisotropic magnetoresistance (AMR) commonly observed in transition ferromagnetic metals, except for two salient features. First, the maximum MR in the present case occurs at an oblique angle between the applied field (H) and electric current (I), while it is usually observed to occur when H parallel to I. Second, the AMR in the plane perpendicular to the film surface displays a remarkable value (Delta rho/rho similar to 8%), which is about an order of magnitude larger than that of the in-plane AMR. Such a large AMR cannot be solely explained by spin-orbit coupling effect. We suggest instead that the metallic and ferromagnetic inhomogeneous granules existing in the BSJ region might have acted as the source of spin-polarized scattering giving rise to the enhanced AMR when the colossal magnetoresistance was measured across the biepitaxial step boundaries. (c) 2006 American Institute of Physics.
Anomalous magnetic ordering in b-axis-oriented orthorhombic HoMnO(3) thin films
(2008-03-31)
Lin, T. H.
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Hsieh, C. C.
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Shih, H. C.
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Luo, C. W.
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Uen, T. M.
Orthorhombic HoMnO(3) films with well-aligned crystallographic orientations were deposited on LaAlO(3)(110) single crystal substrates by using pulsed laser deposition. The nearly perfect b-axis-oriented films provide the opportunity of investigating the orientation-dependent physical property of this material. The temperature dependent magnetization evidently displays an antiferromagnetic ordering near 42 K, irrespective to the direction of applied field. Furthermore, the theoretically expected lock-in transition was clearly observed at around 30 K when field was applied along the c axis and was undetectable along the a and b axes. The 30 K transition was suppressed to 26 K when the applied field increased from 100 to 500 Oe. (C) 2008 American Institute of Physics.
Nonlinear current-voltage characteristics of oxygen-deficient La(0.67)Ca(0.33)MnO(3-y) films
(2008-01-15)
Liu, S. J.
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Juang, J. Y.
;
Lin, J. -Y.
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Wu, K. H.
;
Uen, T. M.
Two different types of nonlinear current-voltage characteristics are observed in oxygen-deficient La(0.67)Ca(0.33)MnO(3-y) (LCMO) films at temperatures below the insulator-metal transition. The paraboliclike dynamic conductance G(V), defined as dI/dV, curves near the zero bias observed in highly oxygen-deficient LCMO films implies the contribution from the spin-dependent tunneling transport between ferromagnetic clusters, with magnetic-disordered regions serving as tunneling barriers. On the other hand, for the slightly oxygen-deficient LCMO films, dips around the zero bias were observed in nonlinear G(V) curves and have been attributed to spin-flip scattering, with oxygen vacancies serving as scattering centers. (C) 2008 American Institute of Physics.
Room-temperature ferromagnetism in Zn and Mn codoped SnO(2) films
(2009-01-01)
Liu, S. J.
;
Liu, C. Y.
;
Juang, J. Y.
;
Fang, H. W.
;
電子物理學系
Room-temperature ferromagnetism was observed in Mn and Zn codoped SnO(2) films grown on c-cut sapphires by using pulsed laser deposition technique. The valence of Mn ions in the codoped films is determined to be 2+ from x-ray absorption near edge spectroscopy. Moreover, the ferromagnetism is affected by the carrier concentration of the films. This result is consistent with the carrier-mediated model. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3056374]
Room-temperature ferromagnetism in Zn and Mn codoped SnO2 films
(2009-01-01)
Liu, S. J.
;
Liu, C. Y.
;
Juang, J. Y.
;
Fang, H. W.
;
電子物理學系
Room-temperature ferromagnetism was observed in Mn and Zn codoped SnO2 films grown on c-cut sapphires by using pulsed laser deposition technique. The valence of Mn ions in the codoped films is determined to be 2+ from x-ray absorption near edge spectroscopy. Moreover, the ferromagnetism is affected by the carrier concentration of the films. This result is consistent with the carrier-mediated model. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3056374]