A magnetization study of the development of short-range order in a concentrated Cu-Mn spin glass

Abstract

The kinetics of short-range order (SRO) growth in a Cu - 16.4 at.% Mn alloy have been studied by measuring the evolution with time of the low-temperature magnetic properties while aging at temperatures around 100 . This new approach was possible because atomic SRO leads to magnetic clustering at this Mn concentration. Several models, all based on the diffusion of vacancies and their annihilation in fixed sinks, implied that the sink density was higher at 115 than at 100 for identical quenching conditions. It was concluded that the quenched-in vacancies condense in clusters. These act as sinks, halting the growth of SRO when the excess quenched-in vacancies have been absorbed. Quenching faster or aging at a higher temperature nucleates more vacancy clusters, causing earlier vacancy exhaustion. Neutron irradiation was used to continuously supply vacancies, thereby driving the SRO process to equilibrium at about 100 . A much higher magnetic susceptibility was attained than previously reported, some 20 times the as-quenched value at the spin freezing temperature.