Three-dimensional Heisenberg critical behavior in amorphous Gd65Fe20Al15 and Gd71Fe3Al26 alloys

Abstract

Amorphous Gd65Fe20Al15 and Gd71Fe3Al26 alloys have ever been reported to exhibit giant refrigerant capacity around their magnetic ferromagnetic-paramagnetic phase transition, which is desirable in magnetic refrigeration. In this paper, we have investigated the critical behavior of amorphous Gd65Fe20Al15 and Gd71Fe3Al26 alloys in order to better understand their magnetic phase transition. We compared the critical exponents estimated using modified Arrott plot and Kouvel-Fisher plot methods. The critical exponents obtained by Widom's law are in good agreement with those calculated from critical isotherm analysis. According to the obtained critical exponents, the magnetic properties of these two samples were re-scaled, indicating that the magnetic behavior of these alloys could be expressed by a universal and unified law. By analyzing the effective critical exponents and exchange interaction of the two alloys, we have determined that Gd65Fe20Al15 and Gd71Fe3Al26 exhibit isotropic short-range magnetic interaction and close to the 3D-Heisenberg model.