Sensitivity enhancement of Co/Pt superlattices through underlayer composition modification

Co/Pt superlattice films for magneto-optical recording have a relatively high Curie temperature compared to rare earth-transition metal films, which has led to criticism of their recording sensitivity at higher disk velocities. We have prepared high-performance Co/Pt disk recording media using (In2O3)(100-x)(SnO2)(x) (ITO) as the underlayer. We have observed a two-fold increase in recording sensitivity as x is increased from 0 to 75 mol % SnO2. We have correlated measured sensitivity behavior with composition-induced changes in the microstructure and electrical resistivity in the ITO underlayer. ITO deposited with low SnO2 content exhibits crystalline microstructure and low electrical resistivity, whereas ITO deposited with high SnO2 content exhibits amorphous microstructure and high electrical resistivity. The reduction in crystallinity with increasing SnO2 content is expected to decrease the ITO thermal conductivity, which can explain the increase in recording sensitivity. Small changes in Co/Pt coercivity as a function of x can easily be compensated by adjusting the ITO sputtering pressure. The optimum combination of Co/Pt sensitivity and coercivity can be readily achieved by controlling the ITO underlayer composition and sputtering pressure. (C) 1996 American Institute of Physics.