SPUTTERING PRESSURE EFFECT ON MICROSTRUCTURE OF SURFACE AND INTERFACE, AND ON COERCIVITY OF CO/PT MULTILAYERS

Thin Co/Pt multilayers were prepared on Si and glass substrates by sputtering with Ar pressures ranging from 2.5 to 15m Torr. The bilayer structure of the samples was Co(3 angstrom)/Pt(15 angstrom) x 17, and all samples had the easy axis of magnetization perpendicular to the sample surface as determined with a SQUID magnetometer. All samples retained the layered structure, as revealed by low-angle x-ray diffraction. In addition, diffraction peaks due to the formation of Co-Pt compounds (presumably at the interfaces between Co and Pt) were identified. The coercivity of samples changed from about 400 Oe for films deposited at low Ar sputtering pressure (2.5 mTorr) to as high as 2300 Oe for films deposited at high Ar pressure (15 mTorr). Ellipsometry and atomic force microscopy were used to study surface roughness and microstructure of samples prepared at different sputtering pressures.