| Abstract
| - A new family of nonstoichiometric materials, GaV4-xMoxS8 (0≤x≤4), 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 (F4̄3m) 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 (1≤x≤3) 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 GaV4-xMoxS8 series.
- Cation substitution at the B-site in GaB4S8 (B = V, Mo) suppresses a low-temperature structural distortion that precedes the onset of long-range magnetic order in the ternary phases. Suppression of this distortion prevents the establishment of a magnetically ordered state in the quaternaries.
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