Effects of a transition layer on CoCr films

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The effects of a transition layer separating the substrate and the columnar structure of rf sputtered CoCr films on their magnetic and structural properties have been investigated. The films were removed from glass substrates and the transition layer was etched directly by rf sputtering. It is shown that the abrupt change or anomalous jump observed in the in-plane magnetization hysteresis loop of some CoCr films is caused by a fine-grained transition layer which is about 1000 Å thick and has a coercivity of 200 Oe. The measured in-plane coercivity increased to 1000 Oe when the transition layer was completely removed while no change was observed in the perpendicular coercivity or saturation magnetization. Only films having a transition layer showed a large decrease in the effective anisotropy field as determined from the in-plane loop when sputter etched to a depth of 2000 Å from the top surface. The dispersion of the hcp (002) axes was found to be 3° for films without and 16° for films with a transition layer. These dispersions were found to be independent of the sputter-etched depth indicating that the intrinsic dispersion of the orientation of CoCr films is established by the transition layer.