An Energy Barrier Model for Write Errors in Exchange-Spring Patterned Media

Bit-patterned media (BPM), in which the medium is patterned into nanometer-sized magnetic islands and each island stores one bit, offers the potential for improved thermal stability. In order to study the write-error rates of systems using BPM, a model that calculates the energy barrier of a single island in exchange-spring or exchange-coupled composite (ECC) BPM, has been developed. The model has been shown to agree well with micromagnetic simulations. A study of energy barriers showed that ECC islands can be designed to retain a greater energy barrier in the presence of an applied field than single layer islands. This indicates that such ECC islands will be less prone to thermally activated adjacent track erasure (ATE) than single layer islands.