Magnetocaloric effect and critical behavior of amorphous (Gd4Co3)1−xSix alloys

The amorphous alloys (Gd4Co3)1−xSix (x=0, 0.05, and 0.10) were prepared by melt spinning. The Curie temperature can be tuned from 213 to 198 K with increasing Si content, while the maximum value of magnetic entropy change for a magnetic field change of 0-5 T can reach 7.3, 7.2 and 6.4 J kg−1 K−1 for x=0, 0.05 and 0.10 respectively. Large values of the refrigerant capacity are obtained in these alloys. The saturation magnetization at 5 K equals 26.5μB, 24.2μB and 22.4μB per (Gd4Co3)1−xSix formula with x=0, 0.05 and 0.10, respectively. All samples undergo a second order ferri-paramagnetic phase transition. The critical behavior around the transition temperature is investigated by means of the modified Arrott plots technique, the Kouvel-Fisher method and the Widom scaling relation. The results indicate that for x=0 and 0.05, the critical exponents are close to those of the 3D Ising model, while the critical exponents for x=0.1 are between those of the 3D Ising model and mean-field model.