  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 130 K 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 300 Oe. 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 5 K to 170 K are caused by an unusual temperature-dependent domain
nucleation field that changes sign around 130 K. The Kerr rotation images of
the magnetic domains confirm that the domain walls depin between 120 K and 140
K.
