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

Highlights: • The martensitic phase of Ni₅₀Mn₃₇Sn₁₃ Heusler alloy was suppressed by Gd doping. • The ferromagnetism in the austenitic phase basically belongs to the mean-field. • Ferromagnetic order can be easily influenced by the magnetically inhomogeneity. - Abstract: The magnetic phase transition behavior were investigated in detail in Ni_50−yGd_yMn₃₇Sn₁₃ (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 (T_C^A) 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 T_C^A = 299.0 ± 0.2 K for y = 1, and β = 0.469 ± 0.068 and γ = 1.214 ± 0.042 with T_C^A = 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