Kavli Affiliate: Gang Su
| First 5 Authors: Jia-Wen Li, Gang Su, Bo Gu, ,
| Summary:
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 LaFeO$_3$, BiFeO$_3$, 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 LaFeO$_3$ 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 AFM insulator, and introduce large magnetic
moments in La(Fe,Mn)O$_3$. For the AFM insulator LaFeO$_3$ 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 LaFeO$_3$ are replaced by the other 3d, 4d transition metal
elements. The large magneto-optical Kerr effect (MOKE) is obtained in these
LaFeO$_3$-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 BiFeO$_3$, SrTcO$_3$, CaTcO$_3$, 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.
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