Magnetic proximity effect in LaO/EuO heterostructures: A first-principles study

Abstract

The heterostructures constructed with superconductor and ferromagnet (S/F) have attracted intensive attention because of their remarkable properties such as spin-triplet pairing at the interface due to the magnetic proximity effect (MPE). Recently, the heteroepitaxial thin films formed by rock-salt rare earth monoxides LaO and EuO were realized in experiments [Kaminaga et al., Chem. Lett. 48, 1244 (2019)], in which LaO is a conventional superconductor with the superconducting ${T}_{c}\ensuremath{\sim}5$ K and EuO is a ferromagnetic insulator with a Curie temperature of 69 K. To elucidate the MPE in the LaO/EuO heterostructure, we have studied its electronic and magnetic properties based on first-principles calculations. The spin splitting of the surface bands as well as the nonzero local magnetic moments on La atoms confirm the existence of MPE. In addition, the electron gases accumulated at the interface and on top of the EuO layer are also spin-polarized. Interestingly, we find that the spin polarization spreads throughout the LaO layers, in which the electron gases in the interstitial regions play an important role. Furthermore, we demonstrate that the net magnetic moment of the LaO layers in the LaO/EuO heterostructure can be effectively modulated by means of an external electric field. These results not only deepen the understanding of the MPE in the LaO/EuO heterostructures, but also suggest that LaO/EuO can serve as a promising platform for studying the Majorana bound states and may apply in the voltage-controlled superconducting switch.