Development and Loss of Ferromagnetism Controlled by the Interplay of Ge Concentration and Mn Vacancies in Structurally Modulated Y4Mn1−xGa12−y
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- 作者：Melanie C. Francisco ; Christos D. Malliakas ; Paula M. B. Piccoli ; Matthias J. Gutmann ; Arthur J. Schultz ; Mercouri G. Kanatzidis
- 刊名：Journal of the American Chemical Society
- 出版年：2010
- 出版时间：July 7, 2010
- 年：2010
- 卷：132
- 期：26
- 页码：8998-9006
- 全文大小：340K
- 年卷期：v.132,no.26(July 7, 2010)
- ISSN：1520-5126
文摘
The cubic intermetallic phase Y4Mn1−xGa12−yGey (x = 0−0.26, y = 0−4.0) has been isolated from a molten gallium flux reaction. It presents a rare example of a system where ferromagnetism can be induced by controlling the vacancies of the magnetic centers. The Y4PdGa12 type crystal structure is made up of a corner-sharing octahedral network of Ga and Ge atoms with Mn atoms at the centers of half the octahedra and Y atoms in the voids. At the highest Ge concentration, y = 4.0, the Mn site is nearly fully occupied, x = 0.05, and the samples are paramagnetic. At a lower Ge concentration, y = 1.0, Mn deficiency develops with x = 0.10. Surprisingly, strong ferromagnetism is observed with Tc = 223 K. When Ge is excluded, y = 0, Mn is substantially deficient at x = 0.26 and ferromagnetism is maintained with a Tc of 160 K. In addition, a 6-fold modulated superstructure appears owing to an ordered slab-like segregation of Mn atoms and vacancies. Corresponding bond distortions propagate throughout the octahedral Ga network. Structure−property relationships are examined with X-ray and neutron diffraction, magnetic susceptibility, and electrical resistivity measurements.