Stable dilute magnetic semiconductor and Curie temperature of 3d transition metal doped strontium titanate perovskite material

Electronic properties and ferromagnetic (FM) state of transition metal (TM) doped strontium titanate SrTiO3 (STO) dilute magnetic semiconductors (DMS) have been investigated using the Korringa-Kohn-Rostoker (KKR) Green's function method. The perovskite type alloys Sr(Ti1−xDx)O3 exhibit stable FM state with V, Cr, Fe, and Co doped cases, whereas spin glass (SG) state is found with Mn doped case. Here D is the 3d TM element and x is the fractional concentration of D in the range of x = 0.01-0.35. Crystal field splitting of 3d electronic states induces magnetic properties into the TM doped STO compounds. Low TC has been found for V, Cr, and Co doped compounds, wherein Fe doped STO shows TC above room temperature for typical concentrations with x > 0.08. Calculated TC in Fe doped STO agrees well with the experimental data. Besides, TC increases with TM concentrations and follows the pattern of square root of doping concentrations at the region of x < 0.1. The uncompensated density of states at the Fermi level are responsible for occurring FM state in the calculated alloys.