Magneto-optical effects of Rh3+ and Rh4+ doped yttrium iron garnet

Abstract

The Faraday rotation and magnetic circular dichroism (MCD) were studied in yttrium iron garnet epitaxial films Y3Fe5O12 doped with trivalent and tetravalent rhodium ions. The magneto-optical effects were measured in the spectral region from 0.5 to 2.5 eV (500–2400 nm) at temperatures between 80 and 300 K. The change in valency of Rh transpired to have a huge effect on the observed magneto-optical phenomena. The contribution from the trivalent Rh ions was very small compared with its tetravalent counterpart. Given the assumption that both the trivalent and tetravalent rhodium ions are in the low-spin state, then the Rh3+(4d6) ions have a negligible magnetic moment and therefore provide only a minor magneto-optical effect. In contrast, strong peaks in the Faraday rotation and MCD spectra are induced in the near infrared and visible regions due to an uncompensated spin moment in the Rh4+(4d5). At photon energies higher than 2.5 eV, the allowed charge transfer transitions to the iron 3d states played a more dominant role with no apparent contribution from the rhodium 4d states.