A 3D micromagnetic model is established to analyze the dynamics of single-pole-type (SPT) heads, in which a main pole and a soft underlayer (SUL) are included. It is found that, in an SPT head whose write pole thickness Lm and pole width W are 40 nm each, the throat height should be no greater than the pole tip width to avoid high remnant field at the static state. The influences of the head's parameters and the damping constant on switching time of SPT head are analyzed respectively. The crystalline anisotropy field of SUL is also proved to have great effect on the switching characteristics: a high anisotropy field along the cross-track direction could stabilize the magnetic moments in SUL and greatly shorten the switching time.

In this work, micromagnetic simulations of writing and reading processes in a perpendicular system including a single pole head and recording media with soft underlayer (SUL) have been performed. The noise contribution from the recording layer increased with increasing grain size distribution of the recording layer but that from soft underlayer remained almost a constant at a given linear density. Details of the noise from the soft underlayer will be discussed. Also thermal decay over a long time scale of the recorded bits was investigated by the Langevin equation and the time-temperature scaling method. It was found that at the linear density of 1058 kfci narrower grain size distribution in the recording layer even in the same average grain size is very important in the point of thermal decay than expectation.