Dielectric tensor characterization and evaluation of several magneto-optical recording media

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Abstract
We attempt to establish a dielectric tensor database for magneto-optical (MO) thin film materials with potential application for blue recording. For this purpose a method is developed for measuring the dielectric tensor of the MO layer within a multilayered stack. It uses a combination of ellipsometric, reflection/transmission, and polar MO Kerr effect measurements, and employs the MULTILAYER computer program to analyze the data. Using this approach we have measured the dielectric tensor for thin films of BiDy3(FeGa)5O12 garnet, MnBi, multilayered Co/Pt, amorphous TbFeCoTa, and fcc cobalt in the wavelength range of 400–780 nm. The dielectric tensor for the Heusler alloy films of PtMnSb, which is available from the published literature, is also presented for the sake of completeness. These materials are then evaluated based on the intrinsic MO figure of merit defined by FOM≡‖εxy‖/(2 Im εxx), where εxx and εxy are the diagonal and off-diagonal elements of the dielectric tensor of the MO material. In the blue–green regime of 400–550 nm, the relationship of the derived FOMs is as follows: FOMMnBi(≊0.027–0.045) ≊ FOMGarnet (≊0.023–0.032) ≳ FOMPtMnSb(≊0.015–0.026) ≳ FOMCo/Pt(≊0.013–0.015) ≊ FOMCo(fcc) (≊0.011–0.016) ≳ FOMTbFeCoTa (≊0.009–0.011).