COERCIVITY ENHANCEMENT OF CO PT SUPERLATTICES THROUGH UNDERLAYER MICROSTRUCTURE MODIFICATION/

A major effort is directed toward Increasing the coercivity of Co/Pt s uperlattice films for practical applications. We have used amorphous I TO as the underlayer and have studied the microstructure and magnetic properties of Co/Pt multilayer film by varying the deposition conditio ns of the underlayer. We have correlated observed microstructural feat ures with coercivity and squareness behavior. A smooth underlayer depo sited at low pressure results in high squareness but low coercivity, w hereas a rough underlayer deposited at high pressure produces Co/Pt fi lms with low squareness but high coercivity. We attribute the increase in coercivity to a decrease in Co/Pt columnar diameter and to enhance d domain wall pinning because of morphology-induced micro-structural d efects such as irregular interfacial and columnar boundaries, and a de crease in columnar diameter. The concurrent reduction in squareness is attributed to a decrease in anisotropy because of degraded crystallin ity and admixture of fcc(200) texture. Underlayer morphology can be ea sily controlled by sputtering pressure for the optimum combination of coercivity and squareness.