Spin Reorientation Transition in Amorphous FeBSi Thin Films Submitted to Thermal Treatments

Magnetic thin films have been obtained by radio-frequency (RF) sputtering on Si₃N₄ substrates from a Fe₇₈B₁₃Si₉ target. The samples, with thickness t varying from 25 to 300 nm, are amorphous; crystalline fraction develops only for t ges 300 nm. Static hysteresis loops have been measured at room temperature by means of an alternating gradient magnetometer. Samples having t >80 nm display a two-slope hysteresis loops: first steep magnetization jump followed by a linear behavior between remanence and saturation revealing the occurrence of a spin-reorientation transition (SRT). The magnetic field H_K at which the saturation is reached is connected with the perpendicular anisotropy. Magnetic force microscopy has been performed on all samples, indicating that for t les80 nm the magnetization lies in the film plane, while for larger thickness, it is oriented perpendicularly to the film plane. In this work, SRT has been studied as a function of sample thickness and perpendicular anisotropy. In particular, the effect of furnace annealing on the transition from in-plane to out-of-plane configuration will be studied in details.