Microstructure and magnetic properties of thin-film Co-Ni-Pt for longitudinal recording

The dependence of microstructure and magnetic properties of RF-sputtered thin films of Co-Ni-Pt deposited on NiP/Al and Cr/NiP/Al substrates was studied as a function of platinum composition, Ar pressure, and sputtering power. Transmission electron microscopy and electron and X-ray diffraction were utilized to determine the correlation between the observed coercivity, remanence squareness behavior, and microstructure. It has been found that in the case of films on NiP/Al substrates, the coercivity is controlled by the grain size, whereas it is dominated by the relative amount of the HCP and FCC cobalt phases for the films deposited on a 300-nm Cr underlayer. An increase in the Ar pressure leads to a further increase in coercivity for both substrates. This behavior was attributed to an increase in the grain size and a more favorable c-axis orientation of the HCP cobalt phase for Cr and NiP underlayers, respectively