Size distribution of Ni precipitates in Ag-Ni alloys determined by maximum entropy analysis of ultra-high field magnetization curves

Supersaturated Ag-Ni solutions containing 10 at.% Ni are produced by electron-beam co-evaporation onto cold glass substrates. Upon annealing the Ni precipitates and coarsens. The magnetization of samples annealed to various temperatures is measured at room temperature in a vibrating sample magnetometer. Samples annealed up to 650 K show superparamagnetic behavior. The size distribution of the 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. When a particle-size-dependent spontaneous magnetization term is incorporated into the model, the portion of the particle size distribution below 4000 /spl Aring//sup 3/ is altered significantly.