Thickness-dependent magnetooptical properties of ion beam sputtered polycrystalline Ce1Y2Fe5O12 films

Polycrystalline cerium-substituted yttrium iron garnet (Ce:YIG, Ce1Y2Fe5O12) films were deposited on synthetic fused silica substrates with various thicknesses using ion beam sputtering, and their roughness, transmissivity, optical constants, microstructure, and their magnetic and magnetooptical properties were measured. Thicker films exhibit cracking due to thermal mismatch stress. A ∼5 nm thick amorphous layer was observed at the interface between Ce:YIG and the substrates, resulting in a non-monotonic thickness dependence of the measured properties. A 338 nm thick Ce:YIG film showed the largest magnetooptical figure of merit defined as the ratio of Faraday rotation angle to absorption coefficient, 127°/dB at a wavelength of 1550 nm, more than three times larger than prior work.