Successive magnetic phase transitions and magnetocaloric effect in the MnNiFeGe alloy

The magnetic system possessing successive phase transitions is expected to achieve a broad refrigeration temperature region. In present paper, the magnetocaloric effect is investigated in a MnNiFeGe alloy, in which the martensitic transformation and the ferromagnetic phase transition of austenite are in adjacent temperature regions. Under a low magnetic field of 0.9 T, this alloy shows a conventional and an inverse magnetocaloric effect simultaneously while only a conventional effect is observed under a magnetic field of 2.0 T, which is due to the magnetic-field-induced metamagnetic transition in the martensite. Metamagnetic phase transitions and potential application in magnetic refrigeration for the MnNiFeGe alloy are discussed.