Pressure induced martensitic transition, magnetocaloric and magneto-transport properties in Mn-Ni-Sn Heusler alloy

In this work, we report the effect of hydrostatic pressure (P)on the martensitic transition in Mn₅₀Ni₄₀Sn₁₀ Heusler alloy using the magnetization and electrical resistivity measurements. Martensitic transition temperature (T_M)is found to shift significantly to higher temperatures with the application of pressure, which reflects the stabilization of the martensite phase. On the other hand, T_M shifts to lower temperatures with magnetic field, which implies the stabilization of the austenite phase. The estimated rate of change of martensitic transition temperature with pressure (dT_M/dP)for the present alloy is ∼4.6 K/kbar. The alloy shows a maximum negative magnetoresistance (MR)of 9.6% for P = 4 kbar at the martensitic transition. A large isothermal magnetic entropy change (ΔS_M)of 16.6 J/kg.K and a refrigerant capacity (RC)of ∼146 J/kg are observed at T_M under ambient pressure. Both quantities are found to decrease with the increase of pressure. The values of ΔS_M and adiabatic temperature change (ΔT_ad), calculated from heat capacity measurements are ∼11.3 J/kg.K and −3.4 K respectively for 50 kOe field change. The observed pressure and field dependence results have been explained using the Clausius-Clapeyron equation. The combined effect of pressure and field on the martensitic transition is also discussed.