Stable room-temperature ferromagnetic phase at the FeRh(100) surface

摘要

Interfaces and low dimensionality are sources of strong modifications ofelectronic, structural, and magnetic properties of materials. FeRh alloys arean excellent example because of the first-order phase transition taking placeat $\sim$400 K from an antiferromagnetic phase at room temperature to a hightemperature ferromagnetic one. It is accompanied by a resistance change andvolume expansion of about 1\%. We have investigated the electronic and magneticproperties of FeRh(100) epitaxially grown on MgO by combining spectroscopiescharacterized by different probing depths, namely X-ray magnetic circulardichroism and photoelectron spectroscopy. We thus reveal that the symmetrybreaking induced at the Rh-terminated surface stabilizes a surfaceferromagnetic layer involving five planes of Fe and Rh atoms in the nominallyantiferromagnetic phase at room temperature. First-principles calculationsprovide a microscopic description of the structural relaxation and the electronspin-density distribution that fully support the experimental findings.