Strong d-d electron interaction inducing ferromagnetism in Mn-doped LiNbO3

Mn-doped LiNbO3 was prepared by ion beam implantation with Mn content of 1 to 5at.%. The samples were ferromagnetic. The maximum atomic magnetic moment was 5.83 mu B/Mn for the samples with Mn content of 3at.% in the implanted layer. Structure characterization using X-ray absorption near edge structure determined that the Mn atoms substituted principally the Li atoms in the LiNbO3 lattice. The magnetic mechanism was understood with the aid of electronic structure calculation using local density approximations plus U method. The calculated results demonstrated that the Mn:LiNbO3 with Mn atom on the Li site is half-metallic ferromagnetic. The calculated magnetic moment per cell agreed well with the experimental results. Spin splitting of the d-states occurred for both the Mn dopant and the Nb atoms. The doped Mn atom interacts strongly with its neighboring Nb atoms. This strong d-d electron interaction can work at long range through the whole crystalline cell.