Critical behavior and magnetocaloric effect of Gd65Mn35-xGex (x=0, 5, and 10) melt-spun ribbons

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 (alpha-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 51 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4740062]