57Fe Mössbauer and Magnetism study of Mo6+ and W6+ substituted four-layer Aurivillius Bi5FeTi3O15 compound.

The present work reports the structural, electrical and magnetic properties of W⁶⁺ and Mo⁶⁺ substituted four-layer Aurivillius compound, Bi₅FeTi₃O₁₅ (BFTO). The oxidation states of the dopants and other elements of BFTO are studied from x-ray photo-electron and ⁵⁷Fe Mössbauer spectroscopy. The substitution resulted in a net increase of magnetic cation (Fe³⁺) from 25% to about 37.5% in BFTO. However, the magnetization measurements indicate the lack of magnetic ordering even down to 2 K. Further, the high temperature (300-1070 K) dielectric study of these compounds reveal the ferroelectric transition temperature decreases with the increase of magnetic cations in BFTO because of hexavalent W⁶⁺ and Mo⁶⁺ substitution at Ti⁴⁺ site. [ABSTRACT FROM AUTHOR]