| Popis: |
Thin films of Co-Pt and Co-Pd have been electrodeposited from alkaline baths based on cobalt amino-citrate complexes and amino-nitrite complexes of the noble metal, on copper substrates coated with Ni-P ACD (10 μm). Co-Pd films can be obtained in a wide range of compositions; both fcc and hcp structures can be present (the last one only for Pd ≤ 16 at%); the lattice constant varies continously with varying composition. The Bragg diffraction peaks are broadened, suggesting a poorly defined crystalline structure or a high density of defects. The grains appear to be homogeneous and regular, their size being generally below 100 nm. Co-Pt films are rich in cobalt; they show a fcc structure with a lattice constant varying discontinously and with a (111) PO. A well defined crystalline structure is obtained, with fine and regular crystallites (size below 100 nm), and sharp Bragg peaks. Differences in microstructure can be related to large differences in magnetic properties. While Co-Pt films show high coercivities (up to 200 kA/m) and high squareness, Co-Pd films, in the whole range of compositions investigated, show very low coercivities and varying squareness. In the Co-Pd system, hysteresis cycles sometimes suggest the presence of two phases with different micromagnetic behaviours and different coercivities; only one of the phases gives the observed value of coercivity. We further investigated the effect of layering through pulsed current deposition; the growth of the different phases could be controlled through control of deposition parameters in the electrodeposition process. Co-Pd films could be promising candidates for thin-film heads in magnetic recording media; their possibilities have not yet been fully assessed, but their magnetic properties, together with their possible high corrosion resistance and good mechanical properties, deserve further studies. |
