Giant magneto-optical Kerr enhancement from films on SiC due to the optical properties of the substrate

TL;DR

This paper demonstrates a significant enhancement of the magneto-optical Kerr effect in films on SiC substrates due to the substrate's optical properties, enabling improved detection and device design in the infrared spectrum.

Contribution

It reveals that SiC substrates can dramatically amplify Kerr signals at specific energies, and predicts similar effects with other substrates and in different spectral ranges.

Findings

Kerr angle enhanced by a factor of 68 in multilayer graphene on SiC

Enhancement occurs at the high-energy edge of SiC's reststrahlen band

Predicted giant Kerr and Faraday effects on metamaterial substrates with n=-1

Abstract

We report a giant enhancement of the mid-infrared (MIR) magneto-optical complex Kerr angle (polarization change of reflected light) in a variety of materials grown on SiC. In epitaxially-grown multilayer graphene, the Kerr angle is enhanced by a factor of 68, which is in good agreement with Kerr signal modeling. Strong Kerr enhancement is also observed in Fe films grown on SiC and Al-doped bulk SiC. Our experiments and modelling indicate that the enhancement occurs at the high-energy edge of the SiC reststrahlen band where the real component of the complex refractive index n passes through unity. Furthermore, since the signal is greatly enhanced when n=1, the enhancement is predicted to exist over the entire visible/infrared (IR) spectrum for a free-standing film. We also predict similar giant enhancement in both Faraday (transmission) and Kerr rotation for thin films on a metamaterial substrate with refractive index n=-1. This work demonstrates that the substrate used in MOKE measurements must be carefully chosen when investigating magneto-optical materials with weak MOKE signals or when designing MOKE-based optoelectronic devices.