Publication Type:Journal Article
Source:Science, Volume 299, Number 5613, p.1719-1722 (2003)
Keywords:Article, bismuth derivative, calculation, crystal structure, device infection, electric conductivity, Ferroelectric materials, Ferromagnetic materials, film, Heterojunctions, iron derivative, lattice constants, magnetic field, Magnetism, Polarization, priority journal, room temperature, Semiconducting bismuth compounds, structure analysis, thickness, thin films, X ray diffraction
Enhancement of polarization and related properties in heteroepitaxially constrained thin films of the ferroelectromagnet, BiFeO3, is reported. Structure analysis indicates that the crystal structure of film is monoclinic in contrast to bulk, which is rhombohedral. The films display a room-temperature spontaneous polarization (50 to 60 microcoulombs per square centimeter) almost an order of magnitude higher than that of the bulk (6.1 microcoulombs per square centimeter). The observed enhancement is corroborated by first-principles calculations and found to originate from a high sensitivity of the polarization to small changes in lattice parameters. The films also exhibit enhanced thickness-dependent magnetism compared with the bulk. These enhanced and combined functional responses in thin film form present an opportunity to create and implement thin film devices that actively couple the magnetic and ferroelectric order parameters.
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