Real-space visualization of thermomagnetic irreversibility within supercooling and superheating spinodals in Mn_1.85Co_0.15Sb using scanning Hall probe microscopy

Abstract

Phase coexistence across disorder-broadened and magnetic-field-induced first-order antiferromagnetic to ferrimagnetic transition in polycrystalline Mn_1.85Co_0.15Sb has been studied mesoscopically by scanning Hall probe microscope at 120 K and up to 5 T magnetic fields. We have observed hysteresis with varying magnetic fields and evolution of coexisting antiferromagnetic and ferrimagnetic states on mesoscopic length scale. These studies show that the magnetic state of the system at low field depends on the path followed to reach 120 K. The low-field magnetic states are mesoscopically different for virgin and second field increasing cycle when 120 K is reached by warming from 5 K but are the same within measurement accuracy when the measuring temperature of 120 K is reached from 300 K by cooling.