Fluctuation fields in perpendicular media

Simulations of experiments to determine the fluctuation field and activation volume in perpendicular media show that the measurement is sensitive to the average grain size and the degree of easy axis distribution in the media, but is largely insensitive to the grain-size distribution, except when the medium is near saturation. Although the fluctuation field varies with the medium magnetization, there is generally no correlation between the size of the grains reversing and the activation volume as measured using the standard technique.