Magnetic anisotropy and magnetization reversal processes in Pt/Co/Pt films

Abstract

The dependence of the magnetic anisotropy, magnetization reversal processes and magnetic domain patterns in Pt/Co(h)/Pt(1 1 1) ultra-thin ferromagnetic films have been studied, as a function of the Co layer thickness d (0.5⩽ d⩽3 nm), by magneto-optical polar Kerr magnetometry and microscopy. The anisotropy constants have been determined from the field-induced coherent rotation magnetization curves measured for different sets of in-plane, H ‖, and perpendicular, H ⊥, applied fields. The particular variation of Kerr rotation and anisotropy at small thickness ( d<0.8 nm) is discussed accounting of CoPt alloying at the interfaces. An abrupt spin reorientation transition from out-of-plane to in-plane has been experimentally evidenced over a narrow range of Co thickness. Irreversibility of the magnetization reversal starting from a demagnetized state and applying positive or negative H ⊥ field is studied from the modifications of the magnetic relaxation and domain patterns. Irreversibility increases with Co thickness, but becomes negligible for an ultra-thin Co layer.