Comparison between different methods for evaluating the anisotropy field distribution in recording systems

The determination of the anisotropy field distribution P(H_α) is made by the second derivative of the magnetization measured perpendicularly to the easy magnetization direction, in the range from saturation to remanence, for a number of magnetic in the same systems. The transverse susceptibility χ(H) is measured in the same systems. For the systems where the particles are “perfectly” aligned the peak of P(H_α) is located at the same field of the peak of χ(H). In the systems where an appreciable fraction of particles are misaligned the peak of P(H_α) is shifted to lower fields while that of χ(H) does not change its position. The coincidence of the two peaks is assumed as a criterion for the validity of the P(Ha) distribution