Field-independent transverse thermal Hall behavior in antiferromagnet YbMnBi₂

YbMnBi₂ is a canted antiferromagnet with a Neel temperature of 290 K and the Curie temperature for spin canting is 250 K. The antiferromagnetic moments are aligned along [001] direction with spin canted along [110] direction. We report measurements of thermal Hall effect with heat flux applied along [1-10] direction, magnetic field along [110] direction, and measured transverse transport signals along [001] direction. We investigated both Nernst effect and thermal Hall effect. In the above configuration, we observed a field-independent thermal Hall conductance plateau around three halves of the thermal conductance quantum with a temperature and magnetic field range approximately from 150 K to 250 K and 1 T to 5 T. Surprisingly, the plateau disappears not only above the Curie temperature, but also at temperatures below 150 K. In the same configuration, we replaced the applied temperature gradient by a current flow and conducted electrical Hall effect measurements for the same sample: the ratio of thermal to electrical Hall effects deviates strongly from the Wiedemann-Franz law. The Nernst conductivity is also much larger in this configuration than when magnetic field is applied along [100] direction, as reported in Ref. 1.

1. Pan, Y., Le, C., He, B., Watzman, S.J., Yao, M., Gooth, J., Heremans, J.P., Sun, Y., Felser, C., 2022. Giant anomalous Nernst signal in the antiferromagnet YbMnBi2. Nature Materials 21, 203–209 (2021). doi:10.1038/s41563-021-01149-2