The crystal growth and magnetic properties of sputtered Co-Ni films on bcc polycrystalline underlayers

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Abstract
The crystal growth and magnetic properties of sputtered Co-20 wt. % Ni films on Cr-based bcc polycrystalline underlayers were investigated. The crystal textures of sputtered Co-Ni films on Cr underlayers were initially determined by x-ray diffraction technique and related to their in-plane coercivities. By introducing N in Cr layers, the lattice spacing of the Cr-based bcc structure was expanded and the effects of larger lattice spacing on the crystal growth of Co-Ni films were studied. The microstructure and morphology of Co-Ni/Cr(N) thin layers were also studied by employing scanning electron microscopy and transmission electron microscopy. The preferred orientation texture of Co-Ni films on Cr(N) layers having d(110)=2.039 Å showed (101̄1), while Cr-N d(110) of larger than 2.039 Å gave (0002) preferred orientation texture of Co-Ni films. In this study, 〈101̄1〉 and 〈0002〉 of 750-Å-thick Co-Ni thin films on Cr(N) bcc polycrystalline layers, which are hard and easy axes of magnetization in the hcp structure, gave 750 and 277 Oe of in-plane coercivity, respectively. The difference in coercivities of Co-Ni films having different crystal textures are clearly explained by the crystal anisotropy in hcp Co-Ni sputtered film.