Dependence ofthe magnetization reversal of Fe/Tb multilayers on layer thicknessand growth temperature

Abstract

Fe/Tb multilayers (MLs) with Fe and Tb layer thicknesses tFe = 1-5 nm and tTb = 1.9 nm are prepared by thermal evaporation at substrate temperatures Ts = 150 (LT) and 300 K (HT), and investigated by means of the magneto-optical Kerr ellipticity, K, at temperatures in the range 50 T300 K. Amorphous Fe, a-Fe, is encountered for tFe<3.0 and 2.5 nm in LT and HT MLs, respectively, a small fraction of which is weakly exchange coupled at all temperatures. Perpendicular magnetic anisotropy (PMA) induced by the antiferromagnetically coupled Fe/Tb interfaces is observed on all MLs unless tFe4 nm, where in-plane anisotropy dominates. In LT MLs with thick a-Fe layers, tFe = 3 nm, a transition from Fe-dominated interface PMA to Tb-dominated bulk PMA with extreme coercivity, Hc>4 MA m-1, is observed below 200 K. Field-induced decoupling effects give rise to peculiar hysteresis cycles in the crossover range 160<T<210 K. In HT MLs, sharp interfaces bear characteristics of the two-dimensional Ising model in the temperature range Tc(a-Fe)200 K<T<Tc(Fe/Tb)330 K.