On the ferromagnetic-paramagnetic phase transition in amorphous iron-rich Fe_100-xzr_x (x=8,9,10) alloys

Abstract

With a view to resolving the controversy (see Kaul, 1987; Fish and Rhyne, 1987) surrounding the nature of the magnetic transition. Tc in amorphous (a-)Fe_100-xZr_x alloys with x=8, 9, 10, published magnetisation data on a-Fe₉₂Zr₈ and a-Fe₉₁Zr₉ alloys have been reanalysed and detailed bulk magnetisation measurements in the critical region have been performed on a-Fe₉₀Zr₁₀. Other workers have claimed that the critical exponents for spontaneous magnetisation, initial susceptibility and critical isotherm, i.e. beta , gamma and delta , respectively, have anomalously large values for a-Fe₉₂Zr₈ and a-Fe₉₀Zr₁₀ alloys, but the authors' data analysis demonstrates that for all the glassy alloys in question the critical exponents beta , gamma and delta possess values that are very close to the three-dimensional Heisenberg values and obey the Widom scaling relation, beta delta = beta + gamma . Consistent with this result, magnetisation data in the critical region do satisfy the magnetic equation of state characteristic of a second-order phase transition. A coherent explanation has been provided for the seemingly contradictory neutron diffraction and magnetisation results within the framework of a model previously proposed by the author. Moreover, recently published thermoelectric power and electrical resistivity data on a-Fe₉₀Zr₁₀ and a-Fe₉₂Zr₈8, respectively, have also been discussed in the light of the present findings.