The effect of the ferromagnetic metal layer on tunnelling conductance and magnetoresistance in double magnetic planar junctions

Abstract

Based on the free-electron approximation, we investigate the effect of the ferromagnetic metal layer on the tunnelling magnetoresistance (TMR) and tunnelling conductance (TC) in the double magnetic tunnel junctions (DMTJs) of the structure NM/FM/I(S)/NM/I(S)/FM/NM, where FM, NM and I(S) represent the ferromagnetic metal, nonmagnetic metal and insulator (semiconductor), respectively. The FM, I(S) and inner NM layers are of finite thickness, while the thickness of the outer NM layer is infinite. The calculated results show that, due to the spin-dependent interfacial potential barriers caused by electronic band mismatch between the various magnetic and nonmagnetic layers, the dependences of the TMR and TC on the thicknesses of the FM layers exhibit oscillations and a much higher TMR can be obtained for suitable thicknesses of FM layers.