Magnetocaloric effect and critical magnetic behavior in Ni-rich Ni-Mn-Sn full Heusler alloy

In search of low-cost, hysteresis-free, broad working temperature magnetocaloric materials, Ni2.24Mn0.76Sn Heusler alloy has been prepared by the conventional arc melting method. The XRD pattern reveals that the sample is crystallized in Fm3<mml:mo><overbar></mml:mover>m space group in L2(1) cubic symmetry. The Maxwell's equation is employed on magnetic isotherms to determine the change in magnetic entropy. This alloy gives a reasonable magnetocaloric effect (Delta SM=1.25 J/Kg-K and RCP=83.87 J/Kg at 3 T) with a large working temperature (67 K at 3 T) near the room temperature. Critical exponents have been calculated using modified Arrott plot, Kouvel-Fisher plot, and critical isotherm analysis to understand the nature of phase transition and exchange interaction, causing magnetic ordering in the system. The values of critical exponents (beta =0.454 +/- 0.015, gamma =1.145 +/- 0.035, delta =3.522 +/- 0.009) and range of exchange interaction (sigma =1.698) fall in between long-range mean-field theory and short-range 3D Heisenberg model, indicating the complex nature of exchange interaction.