The antiferromagnetic-ferromagnetic conversion and magnetostructural transformation in Mn-Ni-Fe-Ge ribbons

Two Mn-Ni-Fe-Ge ribbon samples are prepared. The ribbons reveal the complicated magnetization process with the variation of temperature and magnetic field. Strikingly, the antiferromagnetic-ferromagnetic conversion and competition are observed in the TiNiSi-type phase in these ribbons. The required field to complete the conversion decreases with increasing temperature. When completing conversion, the coupled magnetostructural transformation from the ferromagnetic TiNiSi-type to paramagnetic Ni2In-type state with large magnetic entropy changes near room temperature is achieved for these ribbons. However, it is found that the magnetic field would be difficult to drive ferromagnetic-paramagnetic magnetostructural transformation for these ribbons unlike temperature. (C) 2014 AIP Publishing LLC.