ИСТИНА

The sawtooth or delta chain is a spin chain of vertex-sharing triangles, that can be considered as a segment of highly frustrated kagomé lattice. The distortion of a triangle partially relieves the frustration which results in ferrimagnetic arrangement of the magnetic moments within delta chain. In this work, we first time investigated thermodynamic properties of the iron oxoselenite, Fe2O(SeO3)2, which hosts unique tilted sawtooth chains formed by Fe3+ ions, in mixed octahedral/tetrahedral coordination. Single crystals and powders of Fe2O(SeO3)2 were synthesized by gas transport reaction and hydrothermal technique, respectively, and studied in measurements of magnetization, specific heat and Mössbauer spectroscopy. Prediction of exchange interaction order was made by density functional theory (DFT) calculations. We suggest tilted sawtooth chain model to describe the whole set of experimental data. In our case there is hierarchy of numerous exchange interactions, that influence the observed magnetic response of the compound. Our suggestions have to be verified in future neutron scattering measurements. This work was supported by the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST “MISiS” grant K2–2017–084, by acts 211 of the Government of Russian Federation, сontract No. 02.A03.21.0004