A MAGNETIZATION STUDY OF THE DEVELOPMENT OF SHORT-RANGE ORDER IN A CONCENTRATED CU-MN SPIN-GLASS

The kinetics of short-range order (SRO) growth in a Cu-16.4 at.% Mn al loy have been studied by measuring the evolution with time of the low- temperature magnetic properties while aging at temperatures around 100 degrees C. This new approach was possible because atomic SRO leads to magnetic clustering at this Mn concentration. Several models, all bas ed on the diffusion of vacancies and their annihilation in fixed sinks , implied that the sink density was higher at 115 degrees C than at 10 0 degrees C for identical quenching conditions. it was concluded that the quenched-in vacancies condense in clusters. These act as sinks, ha lting the growth of SRO when the excess quenched-in vacancies have bee n absorbed. Quenching faster or aging at a higher temperature nucleate s more vacancy clusters, causing earlier vacancy exhaustion. Neutron i rradiation was used to continuously supply vacancies, thereby driving the SRO process to equilibrium at about 100 degrees C. A much higher m agnetic susceptibility was attained than previously reported, some 20 times the as-quenched value at the spin freezing temperature.