Effects of underlayer materials and substrate temperatures on the structural and magnetic properties of Nd2Fe14B films
Ma Yun-Gui (马云贵)a, Yang Zheng (杨正)a, M. Matsumotob, A. Morisakob, S. Takeib
a Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000, China; b Department of Information Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
Abstract Thin films of Nd$_2$Fe$_{14}$B were fabricated on heated glass substrates by dc magnetron sputtering. Different material underlayers (Ta, Mo, or W) were used to examine the underlayer influence on the structural and magnetic properties of the NdFeB films. Deposited on a Ta buffer layer at 420℃, the 300 nm thick NdFeB films were shown to be isotropic. But when the substrate temperature $T_{\rm s}$ was elevated to 520℃, the Nd$_2$Fe$_{14}$B crystallites of (00l) plane were epitaxially grown on Ta (110) underlayer. In contrast, Mo (110) buffer layer could not induce any preferential orientation in NdFeB film irrespective of the substrate temperature or film thickness. The W buffer layer was found to be most effective for the nucleation of Nd$_2$Fe$_{14}$B crystallites with c-axis alignment perpendicular to the film plane when $T_{\rm s}$ <490℃. But at $T_{\rm s}$ =490℃ the magnetic layer became isotropic. The maximum coercivity obtained was about 995 kA/m for the 100nm film deposited on W underlayer at 490℃. These variations were tentatively explained in terms of the lattice misfit between the underlayer and the magnetic layer, combined with the considerations of underlayer morphologies.
Received: 18 December 2003
Revised: 21 June 2004
Accepted manuscript online:
Ma Yun-Gui (马云贵), Yang Zheng (杨正), M. Matsumoto, A. Morisako, S. Takei Effects of underlayer materials and substrate temperatures on the structural and magnetic properties of Nd2Fe14B films 2004 Chinese Physics 13 1969
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