Dynamically tunable operating temperature range of Ni-Co-Mn-Sn magnetic shape memory alloys via pressure modulation

Ni-Mn-Sn ferromagnetic shape memory alloys (FSMAs) have recently attracted attention due to their magnetic field-induced reverse martensitic transformation. However, the low and narrow operating temperature range greatly hinders their application, which is challenging to be solved. Here, a novel concept is introduced and demonstrated to increase and dynamically tune the operating temperatures in Ni-Co-Mn-Sn FSMAs via pressure. This work presents a systematic study of the martensitic transformation and magnetic properties in Ni-Co-Mn-Sn FSMAs under the field of hydrostatic pressure by the first principle calculations. Applying pressure allows a dynamically tunable wide operating temperature range in Ni14Co2Mn13Sn3 alloy and Ni13Co3Mn13Sn3 alloy, which results from the improvement of the stability of the martensite. Notably, the operating temperatures of Ni14Co2Mn13Sn3 alloy can be improved from 198 K to a high temperature of 262 K within 3 GPa. The pressure has a weak effect on the martensitic transformation sequence of Ni14Co2Mn13Sn3 (PA-FA-4O-NM) and Ni14Co2Mn13Sn3 (PA-FA-NM). Meanwhile, the pressure can maintain a large magnetization difference (ΔM), which benefits the functional performance in FSMAs. Moreover, in terms of the magnetic properties and the martensitic transformation, the effects of pressure on them are discussed by electronic structure, respectively.