Dielectric tensor characterization of Mn0.53Bi0.47 and Mn0.52Bi0.44Sb0.04 films

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Abstract
We have grown Mn0.53Bi0.47 and Mn0.52Bi0.44Sb0.04 alloy films on glass substrates under UHV conditions. These films exhibit good magneto‐optical (MO) properties. Unfortunately, the measurements of Kerr rotation and ellipticity cannot by themselves provide reliable evaluation of the MO properties of a layer capped with a dielectric SiO film. The purpose of the present work was to determine the dielectric tensor in the MnBi1−xSbx films within a multilayer stack, using a combination of ellipsometric, reflection/transmission, and polar MO Kerr effect measurements in the wavelength range of 360–860 nm. We have evaluated the Mn0.53Bi0.47 and Mn0.52Bi0.44Sb0.04 films based on the intrinsic MO figure of merit (FOM) defined by FOM=‖εxy‖/(2 Im εxx), where εxy and εxx are the diagonal and off‐diagonal elements of the dielectric tensor of the MO material. For short wavelengths (360–550 nm) the measured FOM in the Mn0.53Bi0.47 and Mn0.52Bi0.44Sb0.04 films is significantly larger (≥factor of 2) than that commonly observed in TbFeCo films (∼0.01).