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

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 less than or equal to d less than or equal to 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-parallel to, and perpendicular, H-perpendicular to, 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-perpendicular to 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. (C) 2002 Elsevier Science B.V. All rights reserved.