Influence of interfaces on the perpendicular magnetic anisotropy in Tb/Fe multilayers

Abstract

The influence of interfaces on the perpendicular magnetic anisotropy (PMA) in evaporated Tb/bcc-Fe multilayers with and without diamagnetic Y blocking layers, ${\mathrm{T}\mathrm{b}/\mathrm{F}\mathrm{e}/\mathrm{Y}{}}_{10}$ [=Y(1), Fe-on-Tb], ${\mathrm{Y}/\mathrm{F}\mathrm{e}/\mathrm{T}\mathrm{b}{}}_{10}$ [=Y(2), Tb-on-Fe] and ${\mathrm{T}\mathrm{b}/\mathrm{F}\mathrm{e}{}}_{10}$ [=Y(3)], is investigated using torque magnetometry as a function of the angle \ensuremath{\alpha} between the applied field H and the film plane at temperatures $15\mathrm{K}<~T<~300\mathrm{K}.$ Interface-induced PMA becomes noticeable below the ordering temperatures of the TbFe alloy in the rough Tb/Fe interfaces of Y(1) ${(T}_{C}>~300\mathrm{K})$ and that of Tb at the smooth Tb/Fe interfaces of Y(2) ${(T}_{C}=219\mathrm{K}).$ The latter mechanism dominates at low T, as explained within the framework of a coupled layer model, which is also able to describe the magnetic cone states found in Y(1), Y(2), and Y(3) at $T<100\mathrm{K}.$ In Y(3) the PMA is significantly enhanced by interlayer coupling, leading to polar cone angles as small as 30\ifmmode^\circ\else\textdegree\fi{}.