Scaling of the Magnetoelectric Effect in Chromia Thin Films

Abstract

Scaling behavior of chromia (0001)-oriented films is investigated for film thicknesses ranging from the nanoscale up to the mesoscopic regime. Unusually prominent finite-size scaling of the critical point shift is observed which is accompanied by finite-size effects of magnetic response functions. We investigate the scaling of the antiferromagnetic ordering temperature by reviewing data from the literature and complementing them with our findings. Particular attention is paid to the hitherto unexplored regime of mesoscopic film thicknesses where conventionally no finite-size effects are expected. Results of previously unreported direct measurements of the magnetic susceptibility of chromia thin films grown by molecular beam epitaxy are presented. The magnetometry data reveal qualitative changes in the temperature dependence and peak value of the susceptibility in comparison with the susceptibility of a bulk single crystal. These non-trivial finite-size effects may originate from oxygen defects which accompany reactive sputtering and evaporation growth processes. Significant implications for the scaling behavior of the magnetoelectric effect and consequences for potential spintronic applications are discussed.