A promising magnetic refrigerant, MnCoGe, undergoes consecutive phase transitions from hexagonal to orthorhombic structure at Tt = 400 K1 and from paramagnetic from ferromagnetic ordering at TC = 345 K (in the orthorhombic phase). However, the TC of hexagonal MnCoGe is estimated theoretically to be around 275 K. Once the Tt value falls between TC values of the two polymorphs, a coupling between magnetic and structural phase transitions, i.e. a magnetostructural transition, can be established.2 Consequently, a giant magnetocaloric effect is expected in this kind of material. In contrast to the TC values, the Tt value is easier to tune by changing chemical composition. In this contribution, we demonstrate that Zn doping or vacancy formation on Mn, Co, and Ge sites can be used to achieve magnetostructural coupling in MnCoGe. Based on the room-temperature powder X-ray diffraction patterns, it is found that the hexagonal structure can be induced by both methods. The influence of these chemical modifications on the magnetocaloric effects of MnCoGe-based compounds will also be discussed.

Effects of Zn doping and vacancy formation on the magnetic properties and magnetocaloric effect in MnCoGe

2019 Spring National Meeting

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