Static critical phenomena in ball milled (Fe0.74Cu0.26)(85)Zr-15 amorphousalloy

The magnetic second-order phase transition that occurs at the Curie tempera ture in ball milled amorphous (Fe0.74Cu0.26)(85)Zr-15 metallic alloy has be en investigated. The critical exponents beta, gamma and delta, and the Curi e temperature were obtained using modified Arrot plots in an iterative mann er and embracing the narrow temperature range \T - T-C\/T-C approximate to 0.1. The values of the resulting critical exponents beta, gamma and delta a re in good agreement with those predicted by the mean field theory, indicat ing that the exchange interactions are of long-range type. Furthermore, the temperature dependence of the spontaneous magnetization, determined for th e exponents calculated, was obtained for a wider temperature range from 5 K to the Curie temperature. The presence of spin-wave excitations contributi ng to the thermomagnetization process at low temperatures is suggested by t he mean field theory approach to the temperature dependence of the spontane ous magnetization. We propose a mictomagnetic low-temperature ground state, which appears to be reached through a thermally activated magnetization pr ocess.