ИСТИНА

Low-dimensional systems of heterometallic bonds are fascinating objects of studies in inorganic and solid state chemistry, their presence often leads to unconventional properties. This talk will be focused on mixed chalcogenides based on the 2D heterometallic fragments, e.g. the recently discovered families of nickel-main group metal tellurides Ni3-xMTe2 with x varying from 0 to 1 [1-2]. These compounds are based on the ordered NiAs structure type and, according to the X-ray and HRTEM studies, show different ways of nickel vacancy ordering depending on the type of main group metal they incorporate. For M=Ga we have established hitherto unknown superstructure of the NiAs- type arising from the two-dimensional ordering of the vacancies in the ab crystallographic plane. For M=Sn, a one-dimensional ordering of vacancies is observed, leading to an incommensurate structure. We used these systems as a matrix for incorporating magnetic cations such as iron [3]. Using a high-temperature synthetic approach, we have produced Ni3- xFexMTe2 (M=Ga, Sn) samples with x up to 2. Detailed investigation of the samples using X-ray diffraction, ED, and 57Fe and 112Sn Moessbauer spectroscopy demonstrates the ordered nature of iron incorporation, the ordering patterns differ for M=Ga and Sn. In the case of the former, it was found that at low iron concentrations, all three nickel positions are partially occupied by iron. However, with an increase in the iron content, the process becomes more that of the vacancy filling, so at the limit of iron incorporation (x=1) iron is distributed across those two nickel positions that initially had vacancies (see Figure 1). Iron incorporation into the Ni3-xSnTe2, from all the available data, appears to be less ordered. However, it also does not change the structure motif, and no new superstructure arises from substitution.