Incoherent Magnetic Switching of L10 FePt Grains

In this article, we present a novel micromagnetic model for L10 ordered FePt grains based on their atomic structure. In this model, each monolayer of Fe atoms is represented by a magnetic moment vector and the entire grain consists of a stack of magnetic moments coupled by magnetostatic and nearest-neighbor exchange fields. The grain model enables simulation of incoherent magnetization switching, especially near the Curie temperature. The model is applied to simulate the heat-assisted recording process in granular L10 FePt thin-film media. One of the unique findings is that grains at transition centers could have a domain wall trapped within, provided sufficient grain height. The existence of these grains, whose magnetic moments could be fractional at transition centers, resulting in significant reduction of medium noise. The noise reduction is effectively equivalent to an increase of the number of grains across the read track width. Enhancing and controlling this mechanism by material engineering could lead to significant increase of area density capability, specifically, increase of track density, without decreasing grain size.