Journal ArticleDOI
Ferroelectricity from iron valence ordering in the charge-frustrated system LuFe2O4.
Naoshi Ikeda,Hiroyuki Ohsumi,Kenji Ohwada,Kenji Ishii,Toshiya Inami,Kazuhisa Kakurai,Youichi Murakami,Kenji Yoshii,Shigeo Mori,Yoichi Horibe,Hijiri Kito +10 more
TLDR
Experimental evidence for ferroelectricity arising from electron correlations in the triangular mixed valence oxide, LuFe2O4 is reported, and resonant X-ray scattering measurements are used to determine the ordering of the Fe2+ and Fe3+ ions.Abstract:
Ferroelectric materials have a spontaneous electric polarization and are widely used in electronic devices including memories. Conventional ferroelectricity arises from ionic displacement, but an alternative mechanism has been proposed based on ordered electrons. Evidence for the latter behaviour has now been found in a mixed valence oxide. This type of ferroelectricity may offer potential for devices with enhanced controllability. Ferroelectric materials are widely used in modern electric devices such as memory elements, filtering devices and high-performance insulators. Ferroelectric crystals have a spontaneous electric polarization arising from the coherent arrangement of electric dipoles1 (specifically, a polar displacement of anions and cations). First-principles calculations2,3 and electron density analysis4 of ferroelectric materials have revealed that the covalent bond between the anions and cations, or the orbital hybridization of electrons on both ions, plays a key role in establishing the dipolar arrangement. However, an alternative model—electronic ferroelectricity5—has been proposed in which the electric dipole depends on electron correlations, rather than the covalency. This would offer the attractive possibility of ferroelectric materials that could be controlled by the charge, spin and orbital degrees of freedom of the electron. Here we report experimental evidence for ferroelectricity arising from electron correlations in the triangular mixed valence oxide, LuFe2O4. Using resonant X-ray scattering measurements, we determine the ordering of the Fe2+ and Fe3+ ions. They form a superstructure that supports an electric polarization consisting of distributed electrons of polar symmetry. The polar ordering arises from the repulsive property of electrons—electron correlations—acting on a frustrated geometry.read more
Citations
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Multiferroics: a magnetic twist for ferroelectricity
TL;DR: It is found that even a weak magnetoelectric interaction can lead to spectacular cross-coupling effects when it induces electric polarization in a magnetically ordered state.
Journal ArticleDOI
Multiferroics: progress and prospects in thin films.
TL;DR: Novel device paradigms based on magnetoelectric coupling are discussed, the key scientific challenges in the field are outlined, and high-quality thin-film multiferroics are reviewed.
Journal ArticleDOI
Multiferroicity: the coupling between magnetic and polarization orders
TL;DR: In this article, the authors highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system and summarize various strategies used to combine the two types of order.
Journal ArticleDOI
Advances in magnetoelectric multiferroics.
TL;DR: Progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and usage in applications are reviewed.
Journal ArticleDOI
The evolution of multiferroics
TL;DR: In this article, a review of multiferroic thin-film heterostructures, device architectures, and domain and interface effects is presented. But the focus of the field is now shifting into neighbouring research areas, as discussed in this review.
References
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Book
Introduction to solid state physics
TL;DR: In this paper, the Hartree-Fock Approximation of many-body techniques and the Electron Gas Polarons and Electron-phonon Interaction are discussed.
Journal ArticleDOI
Why Are There so Few Magnetic Ferroelectrics
TL;DR: In this paper, the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence was explored and the properties of known magnetically ordered ferro-electric materials were examined.
Journal ArticleDOI
Origin of ferroelectricity in perovskite oxides
TL;DR: In this paper, the authors report results of electronic-structure calculations on two classic examples of ferroelectric perovskites, BaTiO3 and PbTiO2, and demonstrate that hybridization between the titanium 3d states and the oxygen 2p states is essential for ferroelectivity.
Journal ArticleDOI
Evidence for Pb-O Covalency in Tetragonal PbTiO 3
Yoshihiro Kuroiwa,Shinobu Aoyagi,Akikatsu Sawada,Jimpei Harada,Eiji Nishibori,Masaki Takata,Makoto Sakata +6 more
TL;DR: Clear evidence of the Pb-O hybridization in tetragonal PbTiO3, which has been theoretically predicted as a key factor of much larger ferroelectricity of this substance than that of Ba TiO3 is obtained.