Size distribution of Ni precipitates in AgNi alloys determined by maximum entropy analysis of magnetization curves

Supersaturated Ag-Ni solutions containing approximately 5 at.% Ni are produced by electron-beam co-evaporation onto cold glass substrates. The magnetization of samples annealed to various temperatures is measured at room temperature as a function of applied field in a vibrating sample magnetometer. The magnetization curves of as-deposited samples show superparamagnetic behavior. On annealing, the Ni precipitates completely and coarsens. The volume distribution function of these superparamagnetic Ni particles is extracted from the magnetization curve by applying the maximum entropy method in which the magnetization is modeled as a weighted superposition of Langevin functions. The results are consistent with direct observations in the transmission electron microscope.