Bipolar magnetic semiconductor materials based on 2D Fe2O3 lattice

Abstract

Bipolar magnetic materials play an important role in spintronics. Its unique electronic structure allows the materials to easily regulate fully spin-polarized currents with different spin polarization directions by a gate voltage. It is predicted that 2D monolayer Fe2O3 is a new class of bipolar magnetic semiconductor (BMS) materials by first-principles calculations. The valence band (VB) and the conduction band (CB) have opposite spin polarizations near the Fermi level, and a direct band gap of 0.28 eV between the conduction band bottom (CBM) and the valence band top (VBM). At the same time, the two spin channels have relatively large spin-conserved gaps of 1.05 eV and 2.40 eV. The ground state of the Fe2O3 lattice is a ferromagnetic (FM) state. It has strong intrinsic spin polarization and has a magnetic moment of 10.0 μB per unit cell, and the spin polarization is mainly derived from the transition metal Fe atom. The Bader analysis find that the local magnetic moment of each Fe atom is 4.2 μB, and the local magnetic moment of each O atom is only 0.5 μB. The mechanism of magnetism could be understood by the direct exchange between the orbitals of Fe atom. The Curie temperature (TC) of the Fe2O3 calculated based on Monte Carlo (MC) simulation up to 110 K, which is much larger than the 45 K of CrI3. The characteristics of electrically-controlled polarization currents in bipolar magnetic semiconductor materials have broadened application prospects in the development of spintronics and the construction of bipolar magnetic electronic devices.