Structural, electronic and magnetic properties of RE3+-doping in CoFe2O4: A first-principles study

RE3+(RE=La, Ce, Pr, Nd, Eu, Gd) doped cobalt ferrite (CoFe2O4) have been studied systematically by the first-principles calculations based on density functional theory within the generalized gradient approximation with Hubbard corrections (GGA+U) . The significant effects of RE3+doping on the crystal structure, electronic and magnetic properties of CoFe2O4 have been explored. The calculated results show that the RE ions prefer substituting Fe3+ located at the octahedral sites. And the lattice constant of CoFe1.875RE0.125O4 (RE=La, Ce, Pr, Nd, Eu and Gd) decreases due to the decreasing ionic radius of RE as the atomic number increases. The magnetic properties depend on the unpaired 4f electrons of RE3+ ions. The net magnetic moment of CoFe2O4 increases by doping with Eu and Gd, the reason is that there are more unpaired 4f electrons for Eu3+and Gd3+. However, the net magnetic moment of CoFe2O4 decreases by doping with La, Ce, Pr, and Nd, due to the reason that these RE ions prefer their low spin configurations.