ABSTRACT
The MnNiFeGe alloy is prepared by high-pressure annealing method. It is found that the martensitic transformation temperature after high-pressure annealing of this alloy decreases with the increasing thermal hysteresis. Besides, another magnetic phase transition above the martensitic transformation is observed, which is due to the existence of a large amount of retained austenite induced by high-pressure annealing. As a result, this alloy shows two positive magnetic entropy change peaks, corresponding to the ferromagnetic phase transition of the austenite and the magnetic martensitic transformation, respectively. The magnetic phase transitions, the variable-temperature crystal-structure evolution, and the magnetocaloric properties of this alloy are investigated in detail.
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