Phase equilibria and stability of B2 and L21 ordered phases in the vicinity of half-metallic composition of Co–Cr–Ga Heusler alloy system
Phase equilibria and stability of B2 and L21 ordered phases in the vicinity of half-metallic composition of Co–Cr–Ga Heusler alloy system
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DOI：
10.1016/j.jallcom.2005.05.009
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发表时间：
2005-11
影响因子：
6.2
通讯作者：
K. Kobayashi;R. Kainuma;K. Fukamichi;K. Ishida
中科院分区：
文献类型：
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作者：
K. Kobayashi;R. Kainuma;K. Fukamichi;K. Ishida
近年来，从理论和实践的角度对半金属特性进行了广泛的研究。在本研究中，通过电子探针微量分析（EPMA）、差示扫描量热（DSC）测量和透射电子测量，研究了Co-Cr-Ga体系富Co部分（即半金属成分附近）的相平衡、A2/B2和B2/L21有序-无序转变以及铁磁/顺磁转变。 显微镜（TEM）。平衡状态下γ (A1; fcc-Co)、α (A2; bcc-Cr)、β (B2; CoGa)、ɛ (A3; hcp-Co) 和 σ (D8b) 相的组成、A2/B2 连续有序-无序转变对应的临界组成、B2/L21 有序-无序转变和 L21 相区域的顺磁/铁磁转变已被确定。已证实1000℃时β单相区存在较宽的成分范围，且B2/L21有序-无序转变温度高于Co-Cr-Al系。此外，据透露，CoGa B2 相的相稳定性（根据布拉格-威廉姆斯-戈尔斯基 (BWG) 计算作为连续有序-无序转变温度的线性外推法估计）低于 CoAl。
Recently, half-metallic properties have been extensively investigated from theoretical and practical viewpoints. In the present study, the phase equilibria, A2/B2 and B2/L21order–disorder transition, and ferromagnetic/paramagnetic transition in the Co-rich portion, that is, in the vicinity of half-metallic composition, for Co–Cr–Ga system were examined by electron probe microanalysis (EPMA), differential scanning calorimetric (DSC) measurement, and transmission electron microscope (TEM). The compositions of the γ (A1; fcc-Co), α (A2; bcc-Cr), β (B2; CoGa), ɛ (A3; hcp-Co), and σ (D8b) phases in equilibrium, the critical compositions corresponding to the A2/B2 continuous order–disorder transition, and the critical temperatures of the B2/L21order–disorder transition and the paramagnetic/ferromagnetic transition in the L21phase region have been determined. It has been confirmed that the β single-phase region at 1000°C exists in a wide composition range, and the B2/L21order–disorder transition temperature is higher than that of the Co–Cr–Al system. Furthermore, it has been disclosed that the phase stability of the CoGa B2 phase, estimated from the Bragg–Williams–Gorsky (BWG) calculation as a linear extrapolation of the continuous order–disorder transition temperatures, is lower than that of CoAl.