The magnetostructural transformation and magnetocaloric effect in Co-doped MnNiGe1.05 alloys

A series of MnNi1−x Co x Ge1.05 (x = 0, 0.03, 0.05, 0.07, 0.09, and 0.11) alloys were prepared by the arc-melting method. With increasing content of Co, a first-order magnetostructural transformation between the antiferromagnetic TiNiSi-type phase and the ferromagnetic Ni2In-type phase was observed. A magnetic and crystallographic phase diagram for MnNi1−x Co x Ge1.05 alloys was proposed in this paper. Owing to the abrupt and large jump of magnetization around the magnetostructural transformation, MnNi1−x Co x Ge1.05 (x = 0.07, 0.09, 0.11) alloys show large and positive magnetic entropy changes at relatively low field.