Magnetic Characteristics of Nanocrystalline BiFeO 3 -Based Materials Prepared by Solution Combustion Synthesis
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etic Characteristics of Nanocrystalline BiFeO3-Based Materials Prepared by Solution Combustion Synthesis N. A. Lomanovaa, *, M. V. Tomkovicha, D. P. Danilovichb, A. V. Osipovc, V. V. Panchukd, e, V. G. Semenovd, e, I. V. Pleshakova, M. P. Volkova, and V. V. Gusarova aIoffe
Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia St. Petersburg State Technological Institute (Technical University), St. Petersburg, 190013 Russia c Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, 199034 Russia d St. Petersburg State University, St. Petersburg, 199034 Russia e Institute of Analytical Instrumentation, Russian Academy of Sciences, St. Petersburg, 198095 Russia *e-mail: [email protected] b
Received May 5, 2020; revised August 12, 2020; accepted August 13, 2020
Abstract—Nanocrystalline BiFeO3-based powder materials with an average crystallite size near 40 nm have been prepared by solution combustion synthesis from bismuth and iron nitrates using sucrose and tartaric acid as fuel. The materials have been characterized by X-ray diffraction, helium pycnometry, scanning electron microscopy, energy dispersive X-ray microanalysis, and Mössbauer spectroscopy. Magnetometry results demonstrate that the magnetic response of the materials varies over several orders of magnitude, depending on the synthesis procedure. Keywords: perovskites, bismuth orthoferrite, Mössbauer spectroscopy, magnetometry DOI: 10.1134/S0020168520120110
INTRODUCTION Bismuth orthoferrite (BiFeO3) is the only perovskite-like compound that remains multiferroic above room temperature [1–3]. It has high magnetic ordering (Neel temperature tN ≈ 370°C) and ferroelectric ordering (Curie temperature tC ≈ 830°C) temperatures [1]. At room temperature, BiFeO3 has a rhombohedral structure (sp. gr. R3c), which permits a linear magnetoelectric effect. Its ferroelectric polarization is oriented in the [111] direction of its pseudocubic unit cell. The magnetic moments of the Fe ions are coupled ferromagnetically in the (111) plane and antiferromagnetically between neighboring planes, leading to G-type antiferromagnetic ordering at temperatures below tN. Flexomagnetoelectric interaction in bulk bismuth orthoferrite produces a spatially modulated cycloid spin structure with a period λc = 62 ± 2 nm [4, 5], which suppresses weak ferromagnetism and, accordingly, the linear magnetoelectric effect. Because of this, the preparation of bismuth orthoferrite-based materials whose size state and morphology help suppress the spin cycloid is a topical issue. Factors that influence the magnetic properties of bismuth orthoferrite have been analyzed in many studies (see, for example, Refs. [3, 6–14]). As shown by Wu et al. [3], they depend on nanoparticle size.
According to Castillo et al. [7], BiFeO3 nanoparticles ~50 nm in size, that is, smaller than λc, undergo magnetic ordering and their magnetization exceeds that of bulk bismuth orthoferrite. Hasan et al. [8] interpreted the effect of nanocrystal size on the magnetization of BiF
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