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

Effects induced by a topological insulator Bi₂Se₃ on the magnetic properties of an adjacent GaMnAs film have been investigated using transport measurements. We observed three conspicuous effects in the GaMnAs layer induced by the proximity of the Bi₂Se₃ overlayer. First, our resistivity data as a function of temperature show that the GaMnAs layer adjacent to the Bi₂Se₃ displayed strongly metallic behavior, as compared with the GaMnAs control specimen. Second, the Curie temperature of the GaMnAs in the bilayer was observed to be higher than that of the control layer, in our case by nearly a factor of two. Finally, we observed significant changes in the in-plane magnetic anisotropy of the GaMnAs in the bilayer, in the form of much higher values of both cubic and uniaxial anisotropy parameters. This latter feature manifests itself in a rather spectacular increase of the coercive field observed in magnetization reversal across the in-plane hard axis. These results suggest that proximity of an adjacent Bi₂Se₃ layer represents an important tool for modifying and controlling the ferromagnetic properties of GaMnAs film, and could thus be used to optimize this and similar materials for applications in spintronic devices.