Direct overwrite using through-thickness temperature gradients

A type of direct overwrite using exchange-coupled bilayer magnetooptical media, without the need for an initializing magnetic field, was experimentally demonstrated. This was accomplished at a constant bias magnetic field by manipulating the through-thickness temperature gradient using a combination of short and long laser pulses. One layer of this bilayer medium is rare-earth poor, and the other layer is rare-earth rich without a compensation temperature. With long pulses the magnetization direction of the recording layer is aligned to the external bias magnetic field, while short pulses cause the subnetwork magnetization of the recording layer to be aligned to that of the reference layer by exchange-coupling. The magnetization direction of the reference layer always remains unchanged, while the magnetization of the recording layer is switched by the change between short and long laser pulses