Structural and corresponding magnetic properties of sputtered ni/al multilayer films: effect of ni layer thickness
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A series of Ni/Al multilayers with different thicknesses of Ni layers was produced by a sputtering technique. The deposition parameters of optimum magnetic properties for write heads were detected by scanning the magnetic layer thickness from 0 to 70 nm. The optimum magnetic properties were decided by obtaining the saturation magnetization, M-s, coercivity, H-c and M-s/H-c ratios from the hysteresis loops. A face centered cubic (fcc) structure was established for all films. Transition surface morphology; i.e., a surface morphology between an apical + uneven structure (observed for the mono layered Al film) and an acicular + relatively smooth structure (observed for the films with Ni layer thicknesses of 30 nm and 70 nm) occurred on the surface of the film with Ni layer thickness of 10 nm. This transition surface morphology was very similar to that of the substrate as compared to the other morphologies and it may lead to relatively lower H-c value. A significant increase in H-c value was detected for Ni/Al film with Ni layer thickness of 70 nm. The increase was attributed to the irregular acicular morphology of substrate and high crystallite size of Al fcc (111). The deposition parameters of 8[Ni(10 nm)/Al(10 nm)] multilayer can be considered in order to support the higher M-s/H-c ratio which has a key role for effective technological applications of write heads.