Enhanced Magneto-optical Kerr Effect at Fe/Insulator Interfaces

TL;DR

This study uses density functional theory to demonstrate that Fe/insulator interfaces exhibit an enhanced magneto-optical Kerr effect due to interfacial low-dimensional Fe atoms, which modify optical conductivity components and spin-orbit interactions.

Contribution

The paper reveals a novel mechanism to enhance the magneto-optical Kerr effect at metal/insulator interfaces through low-dimensional interfacial Fe atoms, avoiding heavy elements.

Findings

Significant decrease in diagonal optical conductivity component $\sigma_{xx}$

Enhanced off-diagonal component $\sigma_{xy}$ at around 2 eV photon energy

Large Kerr angle proportional to $\sigma_{xy}/\sigma_{xx}$ ratio

Abstract

Using density functional theory calculations, we have found an enhanced magneto-optical Kerr effect in Fe/insulator interfaces. The results of our study indicate that interfacial Fe atoms in the Fe films have a low-dimensional nature, which causes the following two effects: (i) The diagonal component $\sigma_{xx}$ of the optical conductivity decreases dramatically because the hopping integral for electrons between Fe atoms is suppressed by the low dimensionality. (ii) The off-diagonal component $\sigma_{xy}$ of the optical conductivity does not change at low photon energies, but it is enhanced at photon energies around 2 eV, where we obtain enhanced orbital magnetic moments and spin-orbit correlations for the interfacial Fe atoms. A large Kerr angle develops in proportion to the ratio $\sigma_{xy}/\sigma_{xx}$. Our findings indicate an efficient way to enhance the effect of spin-orbit coupling at metal/insulator interfaces without using heavy elements.