Use of THMap for Write Performance Characterization in HAMR

In heat-assisted magnetic recording, magnetic field-driven magnetization switching of grains in media is assisted by heat provided by laser diode in head. A method called THMap was developed to measure the distribution of magnetization switching of grains. It measures noise power after reverse DC writing over saturated media to the opposite polarity as a function of laser current and write current. We investigated characteristics of THMap by comparing with two-dimensional map of bit error rate (BER) as a function of laser current and write current. To remove the impacts of widened write width on BER by increased laser current, a constant condition of trim writing was conducted from adjacent tracks. Under the trim writing condition, laser current and write current for BER saturation were well correlated with those for the saturation of magnetization switching of grains in THMap. As the results, the saturation of magnetization switching is substantially relevant for BER saturation. These correlation results in the potential of THMap as a method to provide a minimum condition of laser current and write current in its optimization for areal density maximization.