Effects on Ferromagnetic Properties of GaMnAs Induced by Proximity of Topological Insulator Bi₂Se₃

We report the observation of significant changes in magnetic properties of the ferromagnetic semiconductor GaMnAs induced by the proximity of a Bi₂Se₃ layer integrated with the GaMnAs film. Bi₂Se₃/GaMnAs bilayer used in this investigation was grown by molecular beam epitaxy on (001) GaAs substrates and investigated via magnetotransport experiments. In order to identify the effect of Bi₂Se₃ on the magnetic properties of GaMnAs, the Bi₂Se₃ was removed from half of the specimen. This etching process leaves GaMnAs layer serving as a reference. All measurements were carried out simultaneously on the bilayer and the control specimen. The bilayer and the control layer show several different properties, as follows: 1) The GaMnAs in the bilayer was noticeably more metallic than the control layer. 2) The Curie temperature of GaMnAs in the bilayer was significantly higher than that of the control GaMnAs layer. 3) The GaMnAs layer in the bilayer shown much larger coercive fields than the control GaMnAs layer in in-plane magnetization reversal process owing to a strong admixture of cubic magnetocrystalline anisotropy observed in that layer. We ascribe the observed phenomena to proximity effects arising from the presence of the interface between the two materials.