Curie Temperature Distribution in FePt Granular Media

The Curie temperature distribution is an important parameter affecting transition noise in heat-assisted magnetic recording. In this paper, we follow up on our recent report on a technique to evaluate the Curie temperature distribution and provide modeling that validates the method as well as provides the experimental bounds for its validity. Thermal modeling is used to determine whether the technique is sensitive to extrinsic sources of grain temperature variations, such as distributions in thermal boundary resistance. The technique is applied to a variety of FePt granular media films of varying alloy composition and chemical ordering, and we find the Curie temperature distribution to depend primarily on grain ordering kinetics. We also present results of grain switching probability as a function of the applied magnetic field and find a non-trivial dependence on the alloy magnetization.