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標題: Magnetic and Magnetotransport Properties of Exchange-Biased NiFe/NiO Bilayers
作者: Guo, J.Y.
van Lierop, J.
Chang, S.Y.
Lin, K.W.
關鍵字: ion irradiation;composite films
Project: Japanese Journal of Applied Physics
期刊/報告no:: Japanese Journal of Applied Physics, Volume 48, Issue 7.
The magnetism of a series of NiFe (20 nm)/NiO (10 nm) bilayers with different Ni oxides has been studied. Ni oxides were made using ratios of O(2) to Ar ions ranging from 7 to 33% during ion-beam deposition. Transmission electron microscopy (TEM) has shown that with 7% O(2)/Ar used during bottom layer deposition, the film produced consisted of fcc Ni (a = 3.52 angstrom) and rock-salt NiO (a = 4.21 angstrom) phases. A bottom film layer prepared with 33% O(2)/Ar consisted of a pure NiO phase with an expanded lattice constant (a = 4.32 angstrom). A strong temperature dependence of the coercivity (H(c)) and a 20 kOe field-cooled loop shift exchange bias field (H(ex)) were observed below 100 K. In addition, H(ex) increased with increasing O(2)/Ar ratio for the bottom layer antiferromagnetic (AF) component. At 10 K, a NiFe/NiO (33% O(2)/ Ar) bilayer exhibited the higest H(c) (110 Oe) and H(ex) (-60 Oe). This indicated that the more expanded the NiO lattice, the stronger the exchange coupling with the NiFe. The magnetotransport studies have shown that these NiFe/NiO bilayers exhibit anisotropic magnetoresistance (AMR) behavior. In addition, the total MR ratio of these NiFe/NiO bilayers increases with increasing O(2)/Ar ratio owing to strong anisotropic scattering at the NiFe/NiO interface. (C) 2009 The Japan Society of Applied Physics
ISSN: 0021-4922
DOI: 10.1143/jjap.48.073004
Appears in Collections:材料科學與工程學系

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