Phase diagram and magnetocaloric effect of CoMnGe1-xSnxCoMnGe1-xSnx alloys

We propose the phase diagram of a new pseudo-ternary compound, CoMnGe1-xSnxCoMnGe1-xSnx, in the range x⩽0.1x⩽0.1. Our phase diagram is a result of magnetic and calorimetric measurements. We find that the separate magnetic and structural transitions in CoMnGe are tuned together as the level of Sn substitution is increased. We demonstrate the appearance of a hysteretic magnetostructural phase transition in the range x=0.04x=0.04–0.0550.055, similar to that observed in CoMnGe under hydrostatic pressure. From magnetisation measurements, we show that the isothermal entropy change associated with the magnetostructural transition can be as high as 4.5JK-1kg-1 in a field of 1 T. However, the large thermal hysteresis in this transition (∼20K) will limit its straightforward use in a magnetocaloric device.