Probing the anomalous Hall transport and magnetic reversal of quasi-two-dimensional antiferromagnet CoNbS.

The recent discovery of anomalous Hall effect (AHE) in non-collinear antiferromagnets offers a promising platform for developing ultra-compact, ultrafast, and low-power antiferromagnetic spintronics, as well as for the in-depth investigation of topological physics. One notable example is the quasi-two-dimensional antiferromagnet CoNbS, which exhibits a large spontaneous Hall effect with compensated magnetization. Here, we report the observation of a large spontaneous Nernst effect in exfoliated CoNbS flakes. By analyzing the temperature- and field-dependent thermoelectric and transport phenomena, we confirm the intrinsic k-space Berry curvature as the origin of the spontaneous Hall effect. Reflective magnetic circular dichroism measurements further reveal the presence of non-collinear antiferromagnetic domains in CoNbS. Combined with electrical transport measurements, we elucidate the distinct magnetic reversal mechanisms between bulk and exfoliated samples. Our study provides a comprehensive phenomenological understanding of the magnetic and transport properties of CoNbS, laying the groundwork for further exploration of the underlying physics and potential applications of two-dimensional non-collinear magnets.