Enhancing the Magneto-Optical Kerr Effect in Non-collinear Antiferromagnets via a Dielectric Layer

Non-collinear antiferromagnets like, such as Mn₃Sn, exhibit unique magnetic properties, such asincluding the anomalous Hall and magneto-optical Kerr effects (MOKE), where magnetic octupole moments control their interactions with electric currents and light. However, the absence of a net magnetization poses challenges for magneto-optical measurements. In this study, we demonstrated the enhancement of MOKE in Mn₃Sn by adding a dielectric MgO layer with an optimized thickness, creating constructive interference with reflected light. Using ellipsometry, we obtained the refractive index of MgO and performed numerical calculations to predict how the Kerr amplitude changes with MgO thickness. These calculations suggested a sinusoidal dependence, with the amplitude peaking around the optimal thickness. Experimental results from polar MOKE measurements confirmed this trend, showing a doubling of Kerr amplitude at the optimized MgO thickness, which agrees with our model. This work will enable a high-sensitivity detection of magnetic domains, advancing research in antiferromagnetic spintronics.