Engineering the tilt angle in quasi-perpendicularly magnetized Ta/Pt/CoFeB/Pt thin films

Kerr microscopy measurements of Ta/Pt/CoFeB/Pt thin films, with ferromagnetic (FM) CoFeB layer grown by oblique-angle sputter deposition, indicated a quasi-perpendicular magnetic anisotropy. In such a system, the anisotropy is slightly tilted from the normal to substrate plane. The effect of tilt was observed as shift in out-of-plane (OP) room-temperature hysteresis, in presence of in-plane (IP) bias field. Tilt angles were obtained by measuring the shifts in OP hysteresis for several magnitudes and relative azimuthal orientations of bias field with respect to IP projection of tilted anisotropy direction. We studied variation of tilt angle as function of FM layer thickness which was increased near to Spin Reorientation Transition (SRT) value for FM layer in corresponding system. We also studied this variation for different bottom Pt layer thicknesses. The results of our experiment show the variation to follow two different profiles - one monotonic and the other non-monotonic