Effect of Co substitution on thermal stability and magnetocaloric effects of Gd70Al20Fe10-xCox amorphous alloys

The alloys with great magnetocaloric effect (MCE) are expected to be a good alternative for magnetic refrigerantion. In this work, ribbons were prepared by the melt-spinning method using Gd70Al20Fe10-x,Co-x (x = 0, 2, 4, 6, 8 and 10) alloys. Crystal structure, thermal stable, specific heat and magnetic properties of the ribbons were investigated by x-ray diffraction, Dynamic flow differential scanning calorimetry and Physical Properties Measurement System. Results show all samples are in amorphous state, and their onset crystallization temperatures (595-634 K) are higher than the magnetic transition temperature, which contributes to the stable of amorphous structures in practical application. In applied magnetic field of 5 T, the value of magnetic entropy change vertical bar Delta S-M vertical bar increases from 7.1 to 8.7 J . kg(-1). K-1 near the Curie temperature (151-114 K) of Gd70Al20Fe10-xCox alloys (x = 0, 2, 4, 6, 8 and 10) , respectively, which is ascribed to the exchange interaction between magnetic atoms Co and Fe; the full width at half maximum (FWHM) of Delta S-M and refrigeration capacity (RC) increase by 91% and 56% compared with those of pure Gd, respectively; the adiabatic temperature change are in the range of 3.4-3.7 K for the alloys. In addition, all alloys undergo a second order ferroparamagnetic phase transition, which is certified by the Arrott plots and universal curves.