ИСТИНА

Magnetism in low-dimensional magnetic systems is a hot topic due to the wide range of physical phenomena exhibited by them. Usually the magnetic subsystem formation is related to the peculiarities of the crystal structure of the substance. Selenite and tellutite compounds are attractive to the search for low-dimensional magnets due to the strong asymmetric surrounding of selenium or tellurium atoms and presence of active pairs of electrons, which act as nonvisible ligand comparable to the oxygen atom in volume Such electron pairs tend to form cavities, channels or even layers in the crystal structures. As the result, the selenite or tellutire groups also tend to order in the crystal structure. Finally layered (2D) or low-dimensional (1D, 0D) crystal structure may form. The presence of 3d- metal ions in such structure may lead to low-dimensional magnetic subsystem formation and related magnetic properties. In our work, a number of systems with low-dimensional magnetic behavior were prepared and characterized. Copper (II) ions with S = 1/2 compounds Sr2M(SeO3)2Cl2 (M = Co, Ni, Cu), SrCu2(SeO3)2Cl2, CaCu2(SeO3)2Cl2, PbCu2(XO3)2Cl2 (X= Se, Te) and mineral francisite-like compounds with composition Cu3M(SeO3)2O2X (M = different Rare Earth Metals; X = Cl, Br) possess low-dimensional magnetic properties with different geometry of magnetic subsystems. The iron (III) compound S = 5/2 Bi2Fe(SeO3)2OCl3 was found to be quasi one dimensional magnetic. It should be noted, that copper (II) compounds with same formula may crystallize in different crystal structures and exhibit different magnetic properties. For example, PbCu2(SeO3)2Cl2 is isostructural to SrCu2(SeO3)2Cl2, but PbCu2(TeO3)2Cl2 has the same structure as calcium compound CaCu2(SeO3)2Cl2. Magnetic properties of these two types of structures fitted by the different models of spin-spin interactions. The 1D magnetic subsystem of Bi2Fe(SeO3)2OCl3 is closely related to the crystal structure of this compound where [BiO4Cl3] and [BiO3Cl3] polyhedrons and bridged SeO3 groups separate the infinite chains of [FeO6] apex shared octahedrons. Due to such separation, the magnetic interactions between different chains are very weak. The comparison to the other known related compounds will be presented. The work was supported by RFBR project 16-03-00463