NQR in copper halides CuX2 and MCuX3
1980; Elsevier BV; Volume: 58; Linguagem: Inglês
10.1016/0022-2860(80)85032-0
ISSN1872-8014
Autores Tópico(s)Solid-state spectroscopy and crystallography
ResumoWe report our observations of 63,65Cu, 35,37Cl, 79,81Br and 85,87Rb NQR in the quasi 1-D compounds CuBr2, CuCl2, CsCuCl3, CsCuBr3 and RbCuCl3 between 77 and 295 K. The Cu resonance in CuBr2 was observed to disappear Sharply at 82 K, although the Br resonance remained down to 77 K, which is interpreted as heralding the onset of a phase change to the antiferromagnetic (AF) state just below 77 K. This is supported by a rough estimate of TN = 77 K obtained by scaling the known AF transition in CuCl2 at 23.9 K in the ratio of the temperatures, 70 and 226 K respectively, at which CuCl2 and CuBr2 exhibit maxima in magnetic susceptibility. Pressure and temperature dependence data for 63Cu NQR in CuBr2 and CsCuCl3 respectively, are also reported. It is speculated that the exchange narrowing that permits observation of Cu NQR in these Cu2+ (S=12) compounds is linked to their particular type of 1-D halogen bridged structure. Other compounds of the form MCuCl3 and M2CuCl4 characterized by dimer pair Cu2Cl2−6 and discrete molecule CuCl2−4 arrangements were examined unsuccessfully for Cu resonances although chlorine NQR was observed in each case. The RbCuCl3CA) structure (2 Cu sites) appears to be a marginal structure type with a structural phase change at 261 K above which the Cu signals disappeared although Cl NQR was still observed.
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