Title: Magnetoimpedance behavior and its equivalent circuit analysis of Co/Cu/Co/Py pseudo-spin-valve with a nano-oxide layer
Authors: Chien, Wei-Chih
Yao, Yeong-Der
Wu, Jiann-Kuo
Lo, Chi-Kuen
Hung, Ruei-Feng
Lan, M. D.
Lin, Pang
Department of Materials Science and Engineering
Keywords: annealing;cobalt;copper;equivalent circuits;giant magnetoresistance;inductance;Permalloy;spin valves
Issue Date: 1-Feb-2009
Abstract: Magnetoimpedance behaviors and thermal effects of a Co/Cu/Co/Py pseudo-spin-valve (PSV) with a nano-oxide layer (NOL) were studied. The PSV can be regarded as a combination of resistances, inductances, and capacitances. In addition, equivalent circuit theory can be used to analyze the ac behavior of this system. The imaginary part of the magnetoimpedance (magnetoreactance) ratio is more than 1700% at the resonance frequency (f(r))=476 kHz at room temperature (R(T)). The dc magnetoresistance (MR) ratio decreases as the annealing temperature increases because the NOL is formed at the interface between the spacer and the magnetic layer. The NOL deteriorates the differential spin scattering and reduces the dc MR ratio. Impedance spectroscopy was utilized to analyze the capacitance effect from NOL after annealing. The effective capacitance of the PSV was 21.8 nF at R(T) and changed to 11.8 nF after annealing at 200 degrees C. The useful equivalent capacitor circuit not only is a nondestructive measurement technology but can also explain the experimental results and prove the formation of the NOL.
URI: http://dx.doi.org/10.1063/1.3075841
ISSN: 0021-8979
DOI: 10.1063/1.3075841
Volume: 105
Issue: 3
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