Magneto-optical properties and magnetic anisotropy of Nd_05Bi_25Fe_5-yGa_yO_12 thin films on glass substrates

Abstract

Thin films of the highly bismuth-substituted neodymium iron garnet Nd0.5Bi2.5Fe5-yGayO12 (Bi2.5Ga:NIG) were prepared on Nd2BiFe4GaO12 (Bi1Ga1:NIG) buffer layers on glass substrates. These thin films exhibited a large magneto-optical (MO) effect, demonstrating that the magnetic anisotropy of this material can be varied by substituting gallium for iron. As gallium content was increased from 0 to 1, the Bi2.5Ga:NIG thin films showed Faraday rotation angles varying from 21.9 to 14.9°/μm, and effective magnetic anisotropy energy values varying from −3.3 × 104 to 1.3 × 104 erg/cm3. The variation of the effective magnetic anisotropy is discussed in terms of the shape anisotropy depending on the saturation magnetization and the induced magnetic anisotropy caused by the different thermal expansion coefficients for the thin films and the glass substrate. The significant decrease in saturation magnetization upon gallium substitution is believed to result from 85% of the gallium being preferentially substituted at tetrahedral sites in the garnet, which is consistent with changes observed in the Faraday rotation spectra of the thin films.