Irreversible structure change of the as prepared FeMnP 1−x Si x -structure on the initial cooling through the curie temperature

FeMnP0.75Si0.25 experiences a first order para- to ferromagnetic transition at about 200K. In common with some other alloy compositions crystallizing in the Fe2P structure, the magnetic transition of the as prepared alloy occurs at a lower temperature than on subsequent cooling events. This virgin effect is found to be accompanied by a magnetostrictively induced irreversible structure change that persists on succeeding cooling heating cycles. These findings provide means to understand and control the thermal hysteresis of the (Fe1−xMnx)2P1−ySiy alloy system which is a promising material class for use in magnetocaloric refrigerators.