Yttrium iron garnet (YIG) is one of the key materials for applications to spintronic devices due to its characteristic low magnetic damping. Magnetism and magneto optical properties of YIG, with a chemical formula of Y_3Fe_5O_(12), have already been widely investigated experimentally. Theoretical first-principles approach has also been applied to study the magnetism of YIG for the application of spintronic devices, however, there are difficulties to reproduce magnetism of YIG based on first-principles calculations due to the complexity of crystal structure and the strong interaction by the localized J-electron of the Fe atoms in YIG. Regarding the treatment of strong electron correlation, DFT+Umethod has become one of the most effective ways. This method can describe the electronic states by introducing the screened on-site Coulomb interaction in terms of Hubbard model parameter, U_(eff). Previously, we have investigated the on-site Coulomb interaction in several simple transition metal oxides based on constrained DFT approach withm alinear response theory . We have additionally succeeded to describe the electronic structure of YIG and to obtain suitable U_(eff) value. In this work, we compute the magnetism of YIG by using the two values of U_(eff), i.e. 9.8 eV for Fe atoms in octahedral 16(a) sites and 9.1eV for those occupying the tetrahedral 24(d) sites. Calculations were carried out on the basis of the generalized gradient approximation by using full-potential linearized augmented plane wave method .We consider a bcc model of YIu (space group Ia-3d) which contains160 atoms (80 atoms in the primitive cell), and the experimental lattice constant (α = 12.376 A) has been usea m the calculations. Further discussion on magneto crystalline anisotropy and magneto-optical properties of YIG using the computed U_(eff) values will be presented.
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