A magnetic study of precipitation in a gold-cobalt alloy

Abstract

The precipitation kinetics of a gold l·5%, by weight, cobalt alloy have been followed by measuring the sàturation magnetization of the precipitated cobalt and the results are compared with current theories. Marked differences were found between the ageing curves of air and water-quenched specimens. The remanent magnetization, coercive force and field to reduce remanence to zero of aged specimens have been measured and the results are discussed in terms of the single magnetic domain model. The magnetic properties are compared with those of the gold nickel system and the conclusion is reached that the dominant contribution to the anisotropy in the gold cobalt system is due to particle shape. In an appendix the remanence curve and coercivity for a random array of single domain ferromagnetic particles having a linear distribution of anisotropies have been calculated and shown to predict the main features of the observed results.