Different magneto-optical response of magnetic sublattices as a function of temperature in ferrimagnetic bismuth iron garnet films
- In this paper we investigate the magneto-optical (MO) and magnetic properties of bismuth iron garnet Bi3Fe5O12 thin films over a wide range of photon energies (1.6-3.5 eV) and temperatures (5-740 K). Depending on the photon energy range, the Faraday rotation (Theta(F)) and ellipticity (epsilon(F)) vary nonmonotonously with temperature. This behavior cannot be explained by a magnetization variation that can only decrease with increasing temperature. Theta(F) and epsilon(F) spectra have therefore been analyzed using a model based on two optical transitions of a diamagnetic nature, representing the tetrahedral and octahedral iron sites. Thus, the contribution of each magnetic sublattice has been extracted from the global macroscopic MO response and investigated as a function of temperature. The magnetic properties of octahedral and tetrahedral sublattices depend differently on temperature, suggesting a different anisotropy due to oxygen coordination. We have demonstrated that this relatively simple macroscopic measurement with aIn this paper we investigate the magneto-optical (MO) and magnetic properties of bismuth iron garnet Bi3Fe5O12 thin films over a wide range of photon energies (1.6-3.5 eV) and temperatures (5-740 K). Depending on the photon energy range, the Faraday rotation (Theta(F)) and ellipticity (epsilon(F)) vary nonmonotonously with temperature. This behavior cannot be explained by a magnetization variation that can only decrease with increasing temperature. Theta(F) and epsilon(F) spectra have therefore been analyzed using a model based on two optical transitions of a diamagnetic nature, representing the tetrahedral and octahedral iron sites. Thus, the contribution of each magnetic sublattice has been extracted from the global macroscopic MO response and investigated as a function of temperature. The magnetic properties of octahedral and tetrahedral sublattices depend differently on temperature, suggesting a different anisotropy due to oxygen coordination. We have demonstrated that this relatively simple macroscopic measurement with a subsequent analysis can grant access to the information on the properties at a microscopic level. These results can advance the fundamental understanding of MO properties in multisublattice magnetic materials.…
