Enhanced magneto-optical effect in Y1.5Ce1.5Fe5O12 thin films deposited on silicon by pulsed laser deposition

Abstract

Polycrystalline Ce:YIG thin films deposited on silicon are promising material candidates for integrated nonreciprocal photonic devices. So far, the reported Faraday rotation of polycrystalline Ce:YIG thin films on silicon is much lower than that of their single crystal or epitaxial thin film counterparts, limiting the magneto-optical figure of merit, device bandwidth and fabrication tolerance. In this paper, we report the growth of Ce:YIG thin films on silicon from targets with high Ce concentration up to nominally Y1.5Ce1.5Fe5O12 by pulsed laser deposition. The polycrystalline Y1.5Ce1.5Fe5O12 thin film showed pure garnet phase, smooth surface roughness of 0.7 nm, a dominant Ce3+ valence state and a bulk-like saturation magnetization of 125 emu/cm3 at room temperature. This material shows high Faraday rotation of −6410 deg/cm at 1550 nm wavelength, exceeding that of an Y2Ce1Fe5O12 epitaxial thin film on a GGG (100) substrate. However higher loss and lower figure of merit is also observed at 1550 nm wavelength compared to Y2Ce1Fe5O12 thin films, possibly due to the low oxygen partial pressure during fabrication. Low deposition oxygen partial pressure is essential to enhance the Ce solubility and Ce3+ concentration, which results in large Faraday rotation.