Dependence of Switching Fields on Island Shape in Bit Patterned Media

Nanofabricated islands in bit patterned media (BPM) for magnetic data storage tend to vary in shape, size, and material properties which leads to variations in switching fields, causing write errors. In a working system, write errors will be rare, and therefore, an efficient analytic model is preferable to a micromagnetic model. An analytic model has been developed that calculates magnetometric (volume averaged) demagnetizing factors and predicts switching fields for different island shapes, particularly islands that can be described as truncated elliptic cones, since variants of this geometry can represent real islands. The model has been shown to agree well with micromagnetic simulations for various island shapes with fields at various angles to the perpendicular. Switching field calculations reveal that 4 : 1 aspect ratio islands may be more prone to adjacent track erasure compared to those with lower aspect ratios and that islands with slanted side walls were easier to reverse compared to cylindrical ones.