Asymmetric Faraday effect caused by a break of spatial symmetry

TL;DR

This paper reports the discovery of an asymmetric Faraday effect caused by spatial symmetry breaking, leading to unequal Faraday rotations for opposite magnetic states, with potential implications for nanoscale magnonics and optomagnetism.

Contribution

It introduces the concept of asymmetric Faraday effect induced by spatial symmetry-breaking, supported by experimental and numerical evidence in magnetophotonic crystals.

Findings

AFE appears near cavity resonance for oblique incidence.

Asymmetry reaches up to 30% of the Faraday effect.

Effect confirmed across multiple configurations.

Abstract

It is widely known that the magneto-optical Faraday effect is linear in magnetization, and therefore the Faraday angles for the states with opposite magnetizations are of opposite sign but equal in modulus. Here we demonstrate that under certain spatial symmetry-breaking conditions, an asymmetric Faraday effect (AFE) arises, meaning that the Faraday angles for opposite magnetic states differ not only in sign but in absolute value as well. Experimental investigations of AFE are performed in a one-dimensional all-garnet magnetophotonic crystal, where AFE appears in the vicinity of the cavity resonance for an oblique incidence of light with an inclined light polarization plane. The magnitude of the observed asymmetry between Faraday rotations for the two opposite magnetizations is very large and reaches 30$\%$ of the absolute value of the Faraday effect. We confirm the generality of the suggested effect by the numerical analysis of several different configurations in which AFE arises. The discovered AFE is of prime importance for nanoscale magnonics and optomagnetism.