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Zeng F.,Tsinghua University | Sheng P.,Tsinghua University | Tang G.S.,Tsinghua University | Pan F.,Tsinghua University | And 6 more authors.
Materials Chemistry and Physics | Year: 2012

Using first-principles methods, we studied the band and electronic structures and magnetism of Fe-doped LiNbO 3 (LN). It was found that the substitution of Li with Fe in LN was more preferable in terms of energy than the substitution of Nb with Fe and also induced stronger ferromagnetism. The substitution of one Fe atom for one Li atom in a conventional cell would induce an atomic magnetic moment of 5.18 μ B. The main feature that allows Fe substitution for Li is the strong interaction between Fe and its neighboring Nb, which results in strong spin coupling between the two and throughout the whole crystal. Theoretical predictions were tested by experiments in which we doped Fe into LN using ion-beam implantation. It was found that Fe substituted Li fairly well when the doping content was 1 at.%. The obtained maximum atomic magnetic moment arrived to 3.33 μ B/Fe. The discrepancies among the theoretical and experimental results were analyzed. © 2012 Elsevier B.V. All rights reserved.

Chen C.,Tsinghua University | Zeng F.,Tsinghua University | Li J.H.,Tsinghua University | Sheng P.,Tsinghua University | And 6 more authors.
Thin Solid Films | Year: 2011

Mn-doped LiNbO3 was prepared by ion beam implantation with Mn content of 1 to 5 at.%. The samples were ferromagnetic. The maximum atomic magnetic moment was 5.83 μB/Mn for the samples with Mn content of 3 at.% 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. © 2011 Elsevier B.V. All rights reserved.

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