Anomalous depinning of magnetic domain walls within the ferromagnetic phase of the Weyl semimetal Co₃Sn₂S₂

Abstract

We report bulk magnetization measurements and spatially resolved measurements of magnetic domains in Co3Sn2S2 single crystals. The results indicate that a previously reported magnetic anomaly around 130K is due to an anomalous domain wall depinning upon cooling. Our measurements also reveal a hysteresis between field-cooled-cooling (FCC) and field-cooled-warming (FCW) magnetization curves acquired under a constant magnetic field below 300Oe. This observation rules out the possibility that the anomaly stems from a second-order phase transition. Our results further suggest that changes in the shape of hysteresis loops from 5K to 170K are caused by an unusual temperature-dependent domain nucleation field that changes sign around 130K. The Kerr rotation images of the magnetic domains confirm that the domain walls depin between 120K and 140K.

Quantum interactions in topological R166 kagome magnet

“…Even in a long-range ordered magnetic state, some hidden magnetic orders may be induced by the geometric frustration and thermal fluctuation. For instance, the Co-based kagome metal Co 3 Sn 2 S 2 was assumed to be a simple easy-c-axis FM below T C = 175 K [45, 50, 125,137], yet recent studies showed that there exist unconventional magnetic phase transitions at around 130 K [149][150][151][152][153][154]. The µSR experiment, which serves as an extremely sensitive local probe for detecting microscopic details of the static magnetic order, ordered magnetic volume fraction, and magnetic fluctuations, suggested the magnetic phase separation where competing in-plane AFM state coexist with the FM state below T C [150].…”