Critical behavior at the ferromagnetic phase transition of (Fe1-xCrx)85B15 metallic glasses close to the critical concentration of ferromagnetic long-range order.

Abstract

The critical behavior of metallic glasses from the system (${\mathrm{Fe}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Cr}}_{\mathrm{x}}$${)}_{85}$${\mathrm{B}}_{15}$ is studied by measurements of the specific heat, the thermal derivative of the resistivity d\ensuremath{\rho}/dT, the ac susceptibility, and the magnetization in magnetic fields up to 1 T. The absence of a resolvable specific-heat anomaly and a smooth peak in d\ensuremath{\rho}/dT indicates that the metallic glasses exhibit nonuniversal, smeared phase transitions. Nevertheless the magnetization data M(H,T) at high fields show scaling of good quality with effective critical exponents similar to those found in other metallic-glass systems. The Curie temperature determined by the analysis of scaling, however, falls into the temperature range where the low-field magnetic hysteresis measurements clearly show the existence of hysteresis and spontaneous magnetization. The anomalous behavior at the phase transition is attributed to the existence of Fe-Cr concentration fluctuations on a length scale much larger than the random atomic short-range disorder.