Asymptotic and leading "correction-to-scaling" susceptibility critical exponents and amplitudes for ferromagnets with quenched disorder.

Abstract

Accurate values of the asymptotic susceptibility critical exponent (\ensuremath{\gamma}), critical amplitude (\ensuremath{\Gamma}), and the leading ``correction-to-scaling'' exponents and amplitudes for quench-disordered ferromagnets have been determined for the first time through an elaborate analysis of precise and comprehensive ac susceptibility data taken on amorphous ${\mathrm{Fe}}_{\mathrm{x}}$${\mathrm{Ni}}_{80\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{B}}_{19}$${\mathrm{Si}}_{1}$(x =10, 13, and 16) alloys in the critical region. Consequently, the present work provides unambiguous experimental verification of theoretical predictions based on renormalization-group (RG) calculations, and testifies to their correctness by demonstrating that the exponent \ensuremath{\gamma} of the ordered three-dimensional Heisenberg ferromagnet is not affected by the presence of quenched disorder and that the ``frozen'' disorder plays the role of an irrelevant scaling field (in the RG sense).