Giant magnetoresistance and microstructure of FeCo-Al_2O_3 nanogranular films

摘要

The giant magnetoresistance (GMR) and microstructure of FeCo-Al_2O_3 films sputtered at various substrate temperatures (T_s) were investigated. The results indicate that the GMR of as-sputtered FeCo(41 vol.%)-Al_2O_3 granular films reaches the peak value of 6.9%, while for FeCo-Al_2O_3 granular films sputtered at 473 K, the dependence of GMR on volume fraction (f_v) displays 6% peak value with lower content about 35 vol.% FeCo. Based on the features of GMR of FeCo-Al_2O_3 granular films sputtered at different f_v and T_s, an optimum factor A(D_c/L_c) is introduced to explain qualitatively the influence of spin-dependent interface scattering(D) and tunneling barrier's thickness(L) related to f_v, and Ts on GMR. The phase separation of hcp α-Co from bcc α-Fe (Co) was revealed by analytical electron microscopy and its effect on GMR for different f_v and T_s was discussed.