Present and future of magnetooptical recording materials and technology

Erasable optical information storage from amorphous rare earth-transition metal (RE-TM) alloys media has led to impressive improvements towards hyper high density recording in the past five years. Write/erase and readout processes are based on light-induced thermomagnetic switching of magnetic domains and magnetooptical (MO) Kerr effect, respectively, in ferrimagnetic films exhibiting a uniaxial magnetic anisotropy. The route towards ultrahigh optical areal densities was open from the beginning of the nineties from two key technologies related to near field optical techniques and RE-TM exchange-coupled bi, tri- and multilayers. The performances of the MO media depend on the types and states of these multilayers with perpendicular or mixed (perpendicular and planar) anisotropies which change with the temperature and the applied field. The development of the thermomagnetooptical materials is discussed with reference to their magnetic and MO properties to increase the density storage.