Magnetic proximity coupling to Cr-doped Sb2Te3 thin films

Abstract

Using soft x-ray absorption spectroscopy we determined the chemical and magnetic properties of the magnetic topological insulator (MTI) Cr:Sb2Te3. X-ray magnetic circular dichroism (XMCD) at the Cr L2,3, Te M4,5, and Sb M4,5 edges shows that the Te 5p moment is aligned antiparallel to both the Cr 3d and Sb 5p moments, which is characteristic for carrier-mediated ferromagnetic coupling. Comparison of the Cr L2,3 spectra with multiplet calculations indicates a hybridized Cr state, consistent with the carrier-mediated coupling scenario. We studied the enhancement of the Curie temperature, TC, of the MTI thin film through the magnetic proximity effect. Arrott plots, measured using the Cr L3 XMCD, show a TC≈87 K for the as-cleaved film. After deposition of a thin layer of ferromagnetic Co onto the surface, the TC increases to ∼93 K, while the Co and Cr moments are parallel. This increase in TC is unexpectedly small compared to similar systems reported earlier. The XMCD spectra demonstrate that the Co/MTI interface remains intact, i.e., no reaction between Co and the MTI takes place. Our results are a useful starting point for refining the physical models of Cr-doped Sb2Te3, which is required for making use of them in device applications.