This study reviewed the electronic structure using density functional theory (DFT) and demostrated the transmission of optical magnetic circular spectrum in probing spin-dependent optical transitions in yttrium iron garnet (YIG). DFT+Uresults suggested that the t2 orbital of tetrahedral irons are polarized by exchange-splittingO(2p) bands. Such polarization was found to be essential for the kinetic exchange and magnetism in YIG. DFT+Uresults also identified the spin-polarized energy gaps in YIG. On the basis of the distinctions of Fe3O4 [J. Chen et al, Phys. Rev. B, 98, 085 141 (2018)] and YIG in electronic band features along with their manifestations in an optical magnetic circular diachroism (OMCD) spectrum, a map of spin-dependent optical transitions in YIG is presented. Based on the analysis ofOMCDspectra at room temperature, the majority-spin and minority-spin gap in YIG are determined to be 2.45 and 2.25 eV, respectively.
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