Multiferroic properties of the layered perovskite-related oxide La6(Ti0.67Fe0.33)6O20
Abstract
The magnetic and electrical properties of the layered perovskite-related oxide, La6(Ti0.67Fe0.33)6O20, are investigated. The material possesses the structure of six ABO3 layers with iron ions concentrated towards the center of the slabs. The valence state of La, Ti and Fe ions was determined using X-ray photoelectron spectroscopy. The “glassy” magnetic behavior of La6(Ti0.67Fe0.33)6O20 can be understood by the coexistence and competition between two different types of interaction, which originate from both the antiferromagnetic interactions between Fe3+–O–Fe3+ in the central layers of the slabs and ferromagnetic coupling that is induced by the oxygen vacancies from the titanium ion enrichment zone at the borders, owing to the nonrandom distribution of magnetic Fe3+ ions. The observed ferromagnetism can be ascribed to the ferromagnetic coupling and spin canting of the antiferromagnetic coupling via the Dzyaloshinskii–Moriya interaction. The frequency-dependent behavior of the dielectric loss peak in La6(Ti0.67Fe0.33)6O20 manifests itself as a thermally activated relaxation process. The P–E hysteresis loops and local piezoresponse loops confirm the ferroelectric behavior of La6(Ti0.67Fe0.33)6O20.