Authors: Changzheng Wang Xiaoguang Xiao Yonghua Rong T Y Hsu Xu Zuyao
Publish Date: 2006/04/12
Volume: 41, Issue: 12, Pages: 3873-3879
Abstract
A series of FeCo–Al2O3 granular films were prepared with a magnetron controlled sputtering system The magnetic–transport properties and microstructure of films sputtered at various substrate temperatures were characterized by conventional four probes method SQUID magnetometer analytical electron microscope and transmission electron microscope respectively The results indicate that the tunnelling magnetoresistance reaches the peak value of about 69 for FeCo 41 volAl2O3 granular films sputtered at 300 K while for FeCo granular films sputtered at 473 K the 6 peak value in tunnelling magnetoresistance vs volume fraction curve displaces toward the lower FeCo content of about 35 vol Meanwhile FeCo 30volAl2O3 granular films sputtered both at room temperature and at 473 K behave as superparamagnetic and the susceptibility of this film increases with increasing substrate temperature Based on the feature of microstructure of FeCo 41volAl2O3 granular films sputtered at both room temperature and 823 K the evolution sequence of twostage phase separation is suggested In addition the effect of the microstructure on tunnelling magnetoresistance has been discussed
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