Phase transformations, inverse magnetocaloric effect and critical behavior of Ni50Mn36Sn14−xSix Heusler alloys

The magnetic, magnetocaloric and critical behavior properties are systematically investigated for the Heusler alloy system Ni50Mn36Sn14−xSix (x=1, 2 and 3). For all the samples both the normal and inverse magnetocaloric effects (MCE) are observed. The magnetic entropy change and relative cooling power are evaluated near the structural phase transformation and magnetic transition regions under an applied magnetic field of 50 kOe. The maximum magnetic entropy change associated with the martensitic transition are 3.4 J kg−1 K−1, 2.5 J kg−1 K−1 and 1.3 J kg−1 K−1 for x=1, 2 and 3 respectively. The entropy change for x=1, 2 and 3 alloys near the Curie temperature of the austenite phase is found to be −2.8 J kg−1 K−1, −2.7 J kg−1 K−1 and −2.3 J kg−1 K−1 respectively. Relative cooling power is calculated in the vicinity of the Curie temperature of the austenite phase, as well as in the martensitic transition temperature regime. The critical parameters (β, γ and δ) of the samples were determined from the static magnetic data at the second-order ferromagnetic-paramagnetic transition region using the field dependence of magnetic entropy change.