Spin-reorientation transition in ultrathin Tb/Co films

Abstract

A series of terbium (0--6 \AA{})/Co (16 \AA{}) films deposited on Ru(0001) under ultrahigh vacuum conditions and covered by 40 \AA{} Ru have been investigated ex situ by means of the magneto-optic Kerr effect (MOKE). Combined polar and longitudinal loops (dc-MOKE) show a reversible rotation of the remanent magnetization from out-of-plane to in-plane with increasing temperature. The reorientation is continuous and occurs without loss of long-range order. It is discussed in terms of the competition between dipolar demagnetization energy and second- and fourth-order magnetocrystalline anisotropy contributions. The switching of the easy axis of magnetization is confirmed by the susceptibility peak observed in a 10 Oe oscillating field (ac-MOKE) applied perpendicular to the film plane. The transition temperature varies from 323 K (1 \AA{} Tb) to 277 K (6 \AA{} Tb). \textcopyright{} 1996 The American Physical Society.