Dependence of HAMR Transition Curvature on Bit Length

Transition curvature is a major contributor to transition broadening in current heat-assisted magnetic recording (HAMR) devices. In this article, in order to clarify HAMR performance versus bit length (BL), a detailed study of the dependence of HAMR transition curvature on BL is presented. With the help of micromagnetic simulations, HAMR bits with three different BLs (10.5, 15, and 21 nm) are written and transition curvatures are calculated. Both thermal exchange coupling composite (ECC) media and pure FePt media are tested. By tracking the change of transition curvature during the HAMR cooling process, an erase-after-write effect is observed. DC-erased media, introduction of intergranular exchange, and removal of dipole interactions are also examined for potential optimization of the HAMR system.