High temperature ferrimagnetic semiconductors by spin-dependent doping in high temperature antiferromagnets

Abstract

To realize room temperature ferromagnetic (FM) semiconductors is still a challenge in spintronics. Many antiferromagnetic (AFM) insulators and semiconductors with high Neel temperature T_N are obtained in experiments, such as LaFeO₃, BiFeO₃, etc. High concentrations of magnetic impurities can be doped into these AFM materials, but AFM state with very tiny net magnetic moments was obtained in experiments because the magnetic impurities were equally doped into the spin up and down sublattices of the AFM materials. Here, we propose that the effective magnetic field provided by a FM substrate could guarantee the spin-dependent doping in AFM materials, where the doped magnetic impurities prefer one sublattice of spins, and the ferrimagnetic (FIM) materials are obtained. To demonstrate this proposal, we study the Mn-doped AFM insulator LaFeO₃ with FM substrate of Fe metal by the density functional theory (DFT) calculations. It is shown that the doped magnetic Mn impurities prefer to occupy one sublattice of the AFM insulator and introduce large magnetic moments in La(Fe, Mn)O₃. For the AFM insulator LaFeO₃ with high T_N = 740 K, several FIM semiconductors with high Curie temperature T_C > 300 K and the band gap less than 2 eV are obtained by DFT calculations when 1/8 or 1/4 Fe atoms in LaFeO₃ are replaced by the other 3d, 4d transition metal elements. The large magneto-optical Kerr effect (MOKE) is obtained in these LaFeO₃-based FIM semiconductors. In addition, the FIM semiconductors with high T_C are also obtained by spin-dependent doping in some other AFM materials with high T_N, including BiFeO₃, SrTcO₃, CaTcO₃, etc. Our theoretical results propose a way to obtain high T_C FIM semiconductors by spin-dependent doping in high T_N AFM insulators and semiconductors.