Cation Substitution in Defect Thiospinels: Structural and Magnetic Properties of GaV4-xMoxS8 (0x4)

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• 作者：Anthony V. Powell ; Andrew McDowall ; Iwona Szkoda ; Kevin S. Knight ; Brendan J. Kennedy ; Thomas Vogt
• 刊名：Chemistry of Materials
• 出版年：2007
• 出版时间：October 2, 2007
• 年：2007
• 卷：19
• 期：20
• 页码：5035 - 5044
• 全文大小：298K
• 年卷期：v.19,no.20(October 2, 2007)
• ISSN：1520-5002

文摘

A new family of nonstoichiometric materials, GaV_4-xMo_xS₈ (0x4), has been prepared andcharacterized by high-resolution neutron powder diffraction, laboratory and synchrotron X-ray powderdiffraction, thermogravimetry, and SQUID magnetometery. All materials adopt a cubic (F3m) structureat ambient temperature. The end-member phases GaV₄S₈ and GaMo₄S₈ exhibit a distortion to rhombohedral(R3m) symmetry at low temperatures. High-resolution powder neutron diffraction reveals that the phasetransition is incomplete and that both cubic and rhombohedral phases coexist below ca. 40 K. Magneticsusceptibility data indicate that at low temperatures, the end-member phases undergo a transition to aferromagnetic state in which the metal-metal exchange interactions within cubic B₄S₄ clusters arepredominantly antiferromagnetic in origin. At intermediate compositions (1x3) a cubic structure persiststo 4 K, and materials remain paramagnetic to this temperature. The suppression of the rhombohedraldistortion may be responsible for the absence of magnetic ordering observed in the nonstoichiometricmembers of the GaV_4-xMo_xS₈ series.