Magnetic properties and structures of sputtered CoNi/Cr films

This paper describes microstructures and crystalline structures of sputtered CoNi films on sputtered Cr underlayers (CoNi/Cr) and sputtered CoNi films on polyimide (CoNi/pol) relating to magnetic properties at all over the composition range (0-100 at% Ni) determined by transmission electron microscopy (TEM) observation. Magnetic properties of CoNi/Cr and CoNi/pol were studied as a function of Ni content. The maximum Hc value for CoNi/Cr was obtained at about 36 at.% Ni content. Hc values for CoNi/pol were low (below 100 Oe) for all the compositions. CoNi/Cr microstructures were composed of island-like grains (-100 nm) with smaller (-10 nm) sub-grains over all the composition range. On the other hand, no island-like grains were observed in CoNi/pol. Crystalline structures were determined by electron diffraction, wherein CoNi/Cr and CoNi/pol were composed of hexagonal close packed (HCP) phase, a mixture of HCP and faced-centered cubic (FCC) phase, or FCC phase depending on Ni content. Especially, Co64Ni36/Cr, where the maximum Hc was observed, was composed of a mixture of HCP and FCC. The high Hc on CoNi/Cr was relating to microstructures and crystalline structures.