Large magneto-optical Kerr effect in noncollinear antiferromagnets Mn$_{3}X$ ($X$ = Rh, Ir, or Pt)

TL;DR

This study reveals a large magneto-optical Kerr effect in noncollinear antiferromagnets Mn3X, challenging traditional views that such effects are exclusive to ferromagnetic materials, and highlights their potential for novel magneto-optical applications.

Contribution

The paper demonstrates, through first-principles calculations, that Mn3X noncollinear antiferromagnets exhibit large Kerr effects comparable to ferromagnets, due to band degeneracy lifting caused by symmetry breaking.

Findings

Large Kerr rotation angles comparable to ferromagnets.

Origin of Kerr effect linked to symmetry-breaking band degeneracy lifting.

Potential for exploring magneto-optical phenomena in antiferromagnets.

Abstract

Magneto-optical Kerr effect, normally found in magnetic materials with nonzero magnetization such as ferromagnets and ferrimagnets, has been known for more than a century. Here, using first-principles density functional theory, we demonstrate large magneto-optical Kerr effect in high temperature noncollinear antiferromagnets Mn$_{3}X$ ($X$ = Rh, Ir, or Pt), in contrast to usual wisdom. The calculated Kerr rotation angles are large, being comparable to that of transition metal magnets such as bcc Fe. The large Kerr rotation angles and ellipticities are found to originate from the lifting of the band double-degeneracy due to the absence of spatial symmetry in the Mn$_{3}X$ noncollinear antiferromagnets which together with the time-reversal symmetry would preserve the Kramers theorem. Our results indicate that Mn$_{3}X$ would provide a rare material platform for exploration of subtle magneto-optical phenomena in noncollinear magnetic materials without net magnetization.