Twisted magnetization states near the compensation temperature of Fe/Gd multilayers: Anisotropy and surface-termination effects

摘要

Inhomogeneous magnetization depth profiles in antiferromagnetically coupled Fe/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_(Comp)), where the Gd and Fe magnetizations are equal but opposite. While away from T_(Comp) the spin configurations are dictated by the presence of surface- and bulk-twisted states, unusual field dependence is observed near T_(Comp). We used micromagnetic simulations to show that the unusual observed phenomena near T_(Comp) are due to a small uniaxial anisotropy in the Fe layers, whose influence on the spin configurations becomes apparent only near T_(Comp). The simulations also show the onset of the surface- and bulk-twisted phases at temperatures below and above T_(Comp) in agreement with the experimental XMCD data.