Measurement of the magnetocaloric properties of CoMn0.95Fe0.05Si: Large change with Fe substitution

CoMnSi and CoMnSi(1-x)Ge(x) have recently been shown to exhibit negative magnetocaloric properties at a first-order magnetic-field-driven metamagnetic phase transition between a low-temperature antiferromagnetic phase and a high-temperature ferromagnetic phase. We find that doping with Fe changes the magnetocaloric properties drastically by (a) lowering the metamagnetic transition temperature and field, (b) yielding a higher magnetocaloric effect at lower fields than in CoMnSi, and (c) producing an unusual downturn in the entropy change in the highest fields measured. We also find that fragmentation of the sample lowers the transition field reflecting the role of strain in these samples but makes no significant change to the hysteresis loss or the entropy change.