Gd65Mn35−xGex (x = 0, 5, 10) alloy ribbons were prepared by melt-spinning. A fully amorphous structure was obtained for the alloys with x = 5 and 10, whereas, in melt-spun Gd65Mn35 ribbons, crystalline phases (α-Gd and GdMn2) precipitate in the amorphous matrix. The magnetic phase transition from ferromagnetic to paramagnetic is second order. The critical exponents are deduced from the Kouvel-Fisher method and scaling behavior. The obtained critical exponents are in agreement with the theoretical values of 3D Ising model. The Ising-like behavior suggests the presence of large anisotropy and short-range magnetic-coupling behavior. The maximum magnetic-entropy changes of the melt-spun alloys with x = 0, 5, and 10 for a magnetic field change from 0 to 5 T are 4.2, 4.1, and 4.5 Jkg−1 K−1, respectively. All three alloys have a broad temperature range of the magnetic-entropy peak, resulting in large refrigerant capacities.

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Gd5Si2.05−xGe1.95−xNi2x (2x = 0.08, 0.1) alloys were prepared by arc melting followed by annealing at 1273 K for 96 h. Mixed monoclinic Gd5Si2Ge2-type phase, orthorhombic Gd5Si4-type phase, and a small amount of Gd5Si3-type phase were obtained in these alloys. Gd5Si2.01Ge1.91Ni0.08 alloy undergoes a second-order transition (TC) around 300 K, whereas Gd5Si2Ge1.9Ni0.1 alloy exhibits two transitions including a first-order transition (TCІІ) at ∼295 K and second-order transition (TCІ) at ∼301 K. Ni substitution can effectively reduce the thermal hysteresis and magnetic hysteresis while maintaining large magnetic entropy change. The maximum magnetic entropy changes (|ΔSMmax|) of Gd5Si2.05−xGe1.95−xNi2x alloys with 2x = 0.08 and 0.1 are 4.4 and 5.0 J kg−1 K−1, respectively, for 0–2 T, and are 8.0 and 9.1 J kg−1 K−1, respectively, for 0–5 T. Low hysteresis performance and relatively large magnetic entropy change make these alloys favorable for magnetic refrigeration applications.