Relationship Between Applied Field Gradient and Magnetization Switching in ECC Structured Dots

The dependence of the switching of magnetic dots with a composite structure on applied field gradients is investigated. The dot size and magnetic properties were targeted at 2 Tbit/in -class bit patterned media. In the case of a head field with only a perpendicular component, the switching probability can be considered to be the fraction of the dot volume in which the field exceeds the average switching field of the dot when measured in a globally uniform field. The switching probability also depends on the recording field gradient within the dot. On the other hand, in the case of a vector recording field with in-plane components, the switching probability can be approximated by considering the angular dependence of switching field, calculated in a globally uniform field. Additionally, down-track write margins are estimated and found to increase logarithmically as the gradient is increased.