Perpendicular Anisotropy and Damping of MBE-grown MgO/Fe/Au(001) and Au/Fe/Au(001) Trilayers

Abstract

MgO/Fe/Au(001) and Au/Fe/Au(001) trilayers with Fe layer thickness from 0.4 to 1.2 nm were grown by the molecular beam epitaxy (MBE) method, and the perpendicular magnetic anisotropy (PMA) and magnetization dynamics of the trilayers were studied. The MgO/Fe/Au trilayer exhibited a slightly larger interface anisotropy than the Au/Fe/Au trilayer, and the effective anisotropy of both trilayers decreased with increasing Fe thickness due to the shape anisotropy. The g-factor of both trilayers decreased from the bulk value with decreasing Fe thickness, and MgO/Fe/Au showed a slightly lower g-factor than Au/Fe/Au. The effective damping constant a of both trilayers increased with decreasing Fe thickness due to the effect of spin pumping, and interestingly the MgO/Fe/Au trilayers showed large damping compared with the Au/Fe/Au ones. These results suggest that the broken inversion symmetry in MgO/Fe/Au leads to a large PMA and damping through Rashba spin-orbit coupling.