Twisted magnetization states near the compensation temperature ofFe∕Gdmultilayers: Anisotropy and surface-termination effects

Abstract

Inhomogeneous magnetization depth profiles in antiferromagnetically coupled $\mathrm{Fe}∕\mathrm{Gd}$ multilayers are investigated using x-ray magnetic circular dichroism (XMCD) measurements. Spin configurations are studied as a function of temperature and applied field on two multilayers with different termination layers. We place particular emphasis on the vicinity of the ferrimagnetic compensation temperature $({T}_{\mathrm{Comp}})$, where the Gd and Fe magnetizations are equal but opposite. While away from ${T}_{\mathrm{Comp}}$ the spin configurations are dictated by the presence of surface- and bulk-twisted states, unusual field dependence is observed near ${T}_{\mathrm{Comp}}$. We used micromagnetic simulations to show that the unusual observed phenomena near ${T}_{\mathrm{Comp}}$ are due to a small uniaxial anisotropy in the Fe layers, whose influence on the spin configurations becomes apparent only near ${T}_{\mathrm{Comp}}$. The simulations also show the onset of the surface- and bulk-twisted phases at temperatures below and above ${T}_{\mathrm{Comp}}$ in agreement with the experimental XMCD data.