科研之友
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摘要
We present an ab initio theoretical investigation of the magnetization and phase stability of two different complex cubic structures of prototype Cr23C6 and Mn23Th6, with an emphasis on the (Fe,Co,Ni)(23)B-6 and (Fe,Co,Ni)(23)Zr-6 compositions. These phases have recently been observed as secondary or even primary crystallization products of (Fe,Co,Ni)-Zr-B and related metallic glasses that have been studied for applications as soft magnets with nanocrystalline grain size. We first demonstrate the validity of the theoretical technique employed through a detailed comparison between the predictions of the calculations for the Co-Zr binary system and the experimentally stable phases. We then investigate the magnetization and stability of the binary phases. While the Fe-based binary Fe23Zr6 and Fe23B6 phases are expected to have the highest magnetization, the Co-based binary Co23Zr6 and Co23B6 structures are predicted to be the most stable of each prototype. The Co23Zr6 structure is the only binary 23:6 structure predicted to be a stable phase for the (Fe,Co,Ni)(23)B-6 and (Fe,Co,Ni)(23)Zr-6 systems investigated here. Small additions of Zr atoms to the (Fe,Co,Ni)(23)B-6 phases tend to substitutionally occupy the 8c Wykoff site and stabilize these structures. In contrast, small additions of B to the (Fe,Co,Ni)(23)Zr-6 phases have a much weaker site preference and tend to destabilize these structures. As a result, (Fe,Co,Ni)(23)B-6 structures are stabilized in (Fe,Co,Ni)-Zr-B systems relative to the binary (Fe,Co,Ni)(23)B-6 systems while the (Fe,Co,Ni)(23)Zr-6 phases are not. The results presented in this work are in good qualitative agreement with experimental observations of the compositional modifications tending to promote formation of the 23:6 phases in Fe-Co-Zr-B and related metallic glasses.
- 出版日期2008-10
