Micromagnetic-FEM models of a perpendicular writer and reader

We have developed a micromagnetic finite element method (micromagnetic-FEM) to analyze perpendicular magnetic recording (PMR) writers and readers. The head field reversal time is 0.55-0.76 ns including the 0.2-ns current rise, and it is dependent on the current amplitude. The main pole has a faster reversal time, but the yoke and media soft-magnetic underlayer (SUL) show a slower response. In the media recording layer, the trailing region shows a faster reversal due to the longitudinal head field component of the trailing write shield. After writing, the media state affects the remanent field behavior. Since the moving media changes the head-media coupling, the remanent field can be relieved with a long relaxation time within 10 ns. To suppress the remanent field, a good anisotropy control of the main pole and yoke is required. A TMR reader with a flat top shield shows less side-reading, especially when the physical track width is below 0.1 μm. The PMR media plays a role in read width reduction over a wide range of physical track widths.