Room temperature ferromagnetic stability of SrTi1− x M xO3 (M = V, Cr, Mn, Fe, Co, Ni, Cu): A theoretical perspective

The diluted magnetic semiconductor (DMS) has significant potential application in spintronic devices, and DMS oxides have been considered a possibility for high ferromagnetic transition temperature. Here, the first-principles calculation is utilized to comprehensively examine characteristics of high ferromagnetic transition temperature in transition-metal (TM = V, Cr, Mn, Fe, Co, Ni, and Cu)-doped SrTiO3 (STO) at 25%, 12.5%, and 7.4% doping concentrations with respect to their total energy, Curie temperature (TC), formation energy, and Gibbs free energy. We find that high ferromagnetic transition temperature can be obtained in Mn-, Fe-, and Co-doped STO systems with dopant concentration over 7.4%. In addition, TC decreases with the decrease in doping concentration. In particular, above 340 K, Mn-doped STO with 25% doping concentration is in the ferromagnetic state, which resolves the conflict in previous reports that the theoretically calculated Mn-doped STO system has no room-temperature ferromagnetism (RTFM), which has been reported experimentally. V- and Cu-doped STO systems always show the antiferromagnetic ground state. Although the Cr-doped system shows the ferromagnetic ground state at a concentration of 25%, its TC (92.4 K) is much lower than room temperature. Whether Ni-doped STO has ferromagnetism at room temperature needs further experimental verification. The results indicate that Mn-, Fe-, and Co-doped STO systems are very good candidate materials exhibiting RTFM.