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(Ti_0.67Fe_0.33)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(Ti_0.67Fe_0.33)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(Ti_0.67Fe_0.33)₆O₂₀ manifests itself as a thermally activated relaxation process. The P–E hysteresis loops and local piezoresponse loops confirm the ferroelectric behavior of La₆(Ti_0.67Fe_0.33)₆O₂₀.