Electronic-Structure-Driven Magnetic Ordering in a Kondo Semiconductor CeOs2Al10

TL;DR

This study investigates the anisotropic electronic structure changes in the Kondo semiconductor CeOs2Al10 across its antiferromagnetic transition, revealing that structural distortion and energy gap formation along specific axes drive magnetic ordering.

Contribution

It provides new insights into how anisotropic electronic structure and structural distortion influence magnetic ordering in a Kondo semiconductor.

Findings

c-f hybridization gap persists across T0 along a- and c-axes

A new energy gap appears along the b-axis below 39 K

Structural distortion induces the antiferromagnetic order

Abstract

We report the anisotropic changes in the electronic structure of a Kondo semiconductor CeOs$_2$Al$_{10}$ across an anomalous antiferromagnetic ordering temperature ($T_0$) of 29 K, using optical conductivity spectra. The spectra along the $a$- and $c$-axes indicate that a $c$-$f$ hybridization gap emerges from a higher temperature continuously across $T_0$. Along the b-axis, on the other hand, a different energy gap with a peak at 20 meV appears below 39 K, which is higher temperature than $T_0$, because of structural distortion. The onset of the energy gap becomes visible below $T_0$. Our observation reveals that the electronic structure as well as the energy gap opening along the b-axis due to the structural distortion induces antiferromagnetic ordering below $T_0$.