Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

TL;DR

This study demonstrates the saturation of the anomalous Hall effect in RuO₂ at high magnetic fields up to 68 T, revealing field-induced Ne9el vector reorientation in altermagnetic materials.

Contribution

The paper provides experimental evidence of anomalous Hall effect saturation in RuO₂ at high magnetic fields, supported by symmetry analysis and ab initio calculations.

Findings

Anomalous Hall effect observed in RuO₂ thin films.

Saturation of the anomalous Hall signal at approximately 55 T.

Field-induced Ne9el vector reorientation confirmed.

Abstract

Observations of the anomalous Hall effect in RuO$_2$ and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO$_2$ is excluded by symmetry for the N\'eel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the N\'eel vector from the easy-axis towards the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO$_2$ thin-film samples whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field $H_{\rm c} \simeq$ 55 T that was inaccessible in earlier studies, but is consistent with the expected N\'eel-vector reorientation field.