  We examine the thermal origin of the detected "saw-tooth" shaped Hall
resistance (Rxy) signals in the spin-orbit torque switching experiment for
antiferromagnetic MnN. Compared with the results of the heavy metal /
antiferromagnet bilayers (MnN/Ta), the qualitatively same "saw-tooth" shaped
signals also appear in the samples with the heavy metal layer alone (either Ta
or Pt) without MnN layer. In addition, The Rxy signal changes oppositely in the
devices with Ta and Pt, due to the opposite temperature coefficient of
resistivity (TCR) of the two materials. All those results are consistent with
the "localized Joule heating" mechanism in devices with Hall crosses geometry.
Moreover, by utilizing a structure with separated writing current paths and
Hall cross area, the quadratic relationship between delta-Rxy and the writing
current's amplitude is observed, which provides quantitative evidence of the
thermal contribution. These results reveal the dominant thermal artifact in the
widely used Hall crosses geometry for Neel vector probing, and also provide a
strategy to semi-quantitatively evaluate the thermal effect, which can shed
light on a more conclusive experiment design.
