Spacer layer and temperature driven magnetic properties in multilayer structured FeTaC thin films

Abstract

We report the effects of thickness of spacer layers and temperature on the magnetic properties of multilayer structured [FeTaC(50 nm)/Ta(x nm)]n=3/FeTaC(50 nm)/substrate amorphous thin films. A transcritical loop with a large coercivity (HC) of 25 Oe was observed for x = 0 film, but the loop shape was changed to flat loop along with a rapid decrease in HC (<0.25 Oe) by introducing Ta spacer layers. This is attributed to loss of perpendicular anisotropy causing a transition from stripe domain structure to in-plane orientation of spins. Magnetic hysteresis loops measured at different temperatures exhibited a spacer layers' thickness dependent multistep magnetization reversal processes for temperature below 80 K. Thermo- magnetization curves obtained under zero-field-cooled and field-cooled conditions displayed a bifurcation between them for x = 0 film. However, the bifurcation point was shifted to lower temperatures with increasing x and disappeared eventually for films with x ⩾ 4. High-temperature magnetization data revealed no significant changes in the magnetic properties up to Curie temperature. The observed results are elucidated on the basis of change in magnetic structure with the thickness of the spacer layers, pinhole effects at the interface, and temperature, instigating an effective reduction in perpendicular anisotropy and magnetic disorder, and thereby enhancing magnetic properties in multilayer thin films.