The Effect of Hydrostatic Pressure on the Martensitic Transformation and Magnetocaloric Effect of MnNi_0.88GeV_0.12 Alloy

Abstract

The effect of hydrostatic pressure on the martensitic transformation and magnetocaloric properties of MnNi0.88GeV0.12 alloy is studied in detail. X‐ray diffraction at room temperature shows that the alloy has a single hexagonal Ni2In‐type structure. The phase transition temperature moves to the low‐temperature region with the increase in hydrostatic pressure. Under the external magnetic field of 15 kOe, the hydrostatic pressure driving rates d T normalM / d P and d T normalA / d P are 60.25 and 65.25 K GPa−1, respectively, which indicate that the applied pressure expands the working temperature range of magnetic refrigeration. A magnetic entropy change ΔS of −4.8 J kg−1 K−1 is obtained in the external magnetic field of 15 kOe under ambient pressure. The peak value of |ΔS| is increased to 5.6 J kg−1 K−1 under hydrostatic pressure, which is closely related to the structural change of the alloy.

Large magnetocaloric effect near room-temperature by tuning the magneto-structural transition in (Mn, Fe)(Ni, Fe)Si alloy

“…Recent studies on equiatomic alloys (having the general formula M-M′-X, where M & M′ are transition metals and X is the main group element) show that all the stoichiometric compounds undergo a structural transition from orthorhombic crystal symmetry to hexagonal crystal symmetry in the high-temperature region apart from the low-temperature magnetic transition [6][7][8][9][10][11][12][13][14][15][16]. So, in these types of alloys, coupling of the magnetic transition with the structural phase transition is necessary to achieve large MCE due to the large magnetization difference (ΔM) around the transition region [17,18].…”