Magneto-optical Kerr effect, discovered by J. Kerr in 1877, refers to the fact that when a linear polarized light beam hits a magnetic material the polarization plane of the reflected light beams rotates. Nowadays Magneto-optical Kerr effect is widely used as a powerful probe of the electronic and magnetic properties of materials, such as domain wall, surface plasma resonance, magnetic anisotropy and topological insulator. However, magneto-optical Kerr effect has been found only in magnetic materials with nonzero magnetization such asferromagnets and ferrimagnets. Using first-principles density functional theory, Guang-Yu Guo (a DCS of the NCTS) and his co-workers [1] recently demonstrate for the first time large magneto-optical Kerr effect in high-temperature noncollinearantiferromagnets Mn3X (X = Rh, Ir, Pt), in contrast to conventional 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 band double degeneracy due to the absence of spatial symmetry in the Mn3X noncollinearantiferromagnets which together with the time-reversal symmetry would preserve the Kramers theorem. Our results indicate that Mn3X would provide a rare material platform for exploration of subtle magneto-optical phenomena in noncollinear magnetic materials without net magnetization.
Ref and link: W. Feng, G.-Y. Guo, J. Zhou, Y. Yao and Q. Niu, Phys. Rev. B 92, 144426 (2015)
(Prof. Guang-Yu Guo is a Distinuished Center Scientist of NCTS, and also a professor in National Taiwan University).
Figure Caption: Cubic L12 crystal structure of Mn3X (X = Rh, Ir, Pt) with (a) T1 and (b) T2 spin configurations, as well as the corresponding (111) planes in (c) and (d), respectively. The red balls (each with one arrow) and green balls (without arrow) represent Mn and X atoms, respectively. The dashed lines in (c) and (d) stand for the primitive cell of the kagome lattice.
