Magnetocaloric and critical behavior in the austenitic phase of Gd-doped Ni50Mn37Sn13 Heusler alloys

The magnetic phase transition behavior were investigated in detail in Ni50−yGdyMn37Sn13 (y = 1 and 3) alloys prepared by arc-melting method. The martensite phase was found to be strongly suppressed by a small amount of Gd doping. Based on isothermal magnetization curves around Curie temperature of the austenite (TCA) phase, critical behavior in the austenite phases of both alloys were determined carefully by the Kouvel-Fisher method. The critical exponents were found to be β = 0.473 ± 0.020 and γ = 1.141 ± 0.017 with TCA = 299.0 ± 0.2 K for y = 1, and β = 0.469 ± 0.068 and γ = 1.214 ± 0.042 with TCA = 302.9 ± 0.7 K for y = 3, respectively. The values of the critical exponents for the ferromagnetic phase transition in the A phase of two alloys can be basically ascribed in the mean-field model (with β = 0.5, γ = 1) with slightly deviation, revealing a long-range order of ferromagnetic interactions. Such critical behavior can be attributed to the magnetic inhomogeneities originated from the atomic disorder introduced by Gd doping.