The majority of bismuth-containing compounds with a layered perovskite-like structure, analogues of the so-called Aurivillius phases, are of practical and theoretical interest owing to their ferroelectric properties. Bismuth niobate Bi 5 Nb 3 O 15 belongs to the group of mixed layered compounds. Its structure is characterized by the ordered alternation of fragments formed by one and two niobium-oxygen octahedra. Magnetic properties and NEXAFS of cobalt-containing solid solutions with a layered perovskite-like structure Bi 5 Nb 3−3x Co 3x O 15−δ have been studied. Solid solutions of Bi 5 Nb 3−3x Сo 3x O 15−δ (х ≤ 0.005) can be crystallized in tetragonal syngony (sp. gr. P4 / mmm), as cobalt content increases, monoclinic distortion of the unit cell emerges at 0.005 < х ≤ 0.04. The solid solutions as well as cobalt oxides СoO, Co 3 O 4 were studied by the NEXAFS spectroscopy. The analysis of the NEXAFS Co2p-spectra of cobalt-containing solid solutions and cobalt oxides revealed that the studied Co atoms were mainly in the +2 and +3 oxidation state. The isotherms of paramagnetic component of magnetic susceptibility of cobalt atoms in Bi 5 Nb 3−3x Co 3x O 15−δ are typical for antiferromagnets. The effective magnetic moments of single cobalt atoms calculated by extrapolating concentration dependencies of [χ para (Co)] to infinite dilution of the solid solutions exceed pure-spin values and increase as the temperature increases from 6.18 μB (90 K) to 6.69 μB (320 K). The formation of exchangebound aggregates of Сo(III) and Co(II) atoms predominantly with antiferromagnetic exchange types has been found in the solid solutions.
Most bismuth compounds with layered perovskite-like structure, analogs of Aurivillius phases, exhibit ferroelectric properties and are of interest from both practical and theoretical points of view. In this study, we carried out magnetochemical measurements of an electronic state and exchange interactions between iron atoms in the solid solutions , and tetramers, J tetr = -40 cm -1 and J tetr = 25 cm -1 correspondently.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.