Proximity effects on dimensionality and magnetic ordering in Pd/Fe/Pd trialyers

Abstract

The element-specific magnetization and ordering in trilayers consisting of 0.3--1.4 monolayer (ML) thick Fe layers embedded in Pd(001) has been determined using x-ray resonant magnetic scattering. The proximity to Fe induces a large moment in the Pd which extends $\ensuremath{\sim}2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$ from the interfaces. The magnetization as a function of temperature is found to differ significantly for the Fe and Pd sublattices: The Pd signal resembles the results obtained by magneto-optical techniques with an $\mathit{apparent}$ three-dimensional (3D) to two-dimensional (2D) transition in spatial dimensionality for Fe thickness below $\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{ML}$. In stark contrast, the Fe data exhibits a $2\mathrm{D}$ behavior. No ferromagnetic signal is obtained from Fe below the $2\mathrm{D}$ percolation limit in Fe coverage $(\ensuremath{\sim}0.7\phantom{\rule{0.16em}{0ex}}\mathrm{ML})$, while Pd shows a ferromagnetic response for all samples. The results are attributed to the temperature dependence of the susceptibility of Pd and a profound local anisotropy of submonolayered Fe.