Modification of the electronic structure during the AFM-FM transition as a cause of variations in the optical reflectivity in B2-FeRh

We propose to investigate the role of Rh composition and the change of the electronic structure during the magnetostructural AFM–FM transition of FeRh thin films. B2-FeRh is a model system with a well-known metamagnetic transition near room temperature, making it relevant for spintronics and solid-state refrigeration. In prior work, we could show that the AFM–FM transition is accompanied by a measurable reduction in the number of Rh 4d-holes.
To systematically explore this sensitivity, we have fabricated a compositionally graded FeRh thin film by magnetron sputtering and characterized its transition via high-throughput MOKE, revealing a strong composition-dependent change of the optical reflectivity linked towards the magnetic phase. With this proposal, we aim to directly correlate these optical signatures with modifications of the Rh 4d electronic structure using Rh L₂,₃-edge XAS and XMCD at beamline ID12.