HAMR switching dynamics and the magnetic recording quadrilemma

We investigate the dynamical switching process of Heat Assisted Magnetic Recording (HAMR) by numerical calculations of switching probability using an atomistic model. Calculations show that at the elevated write temperature of HAMR there is a loss of information arising from ’backswitching’: a thermodynamic phenomenon which comes into play when the ratio of the Zeeman energy to the thermal energy is insufficiently large to completely stabilise the switched direction. We consider the special case of Heated Dot Magnetic Recording, where a reduction of switching probability can be related to a bit error rate. We show that the backswitching becomes more pronounced at faster write times. Also, we show that in the case of current recording media, based on the binary alloy FePt, backswitching will be a more stringent limitation on recording density than the usually assumed thermal stability criterion.