Author
W. Eerenstein
Bio: W. Eerenstein is an academic researcher from University of Cambridge. The author has contributed to research in topics: Dielectric & Thin film. The author has an hindex of 8, co-authored 9 publications receiving 7737 citations.
Papers
More filters
TL;DR: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements that arises through the quantum mechanical phenomenon of exchange.
Abstract: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.
6,813 citations
TL;DR: Electrically induced giant, sharp and persistent magnetic changes are demonstrated at a single epitaxial interface in ferromagnetic 40 nm La(0.67)Sr( 0.33)MnO(3) films on 0.5 mm ferroelectric BaTiO( 3) substrates, and X-ray diffraction confirms strain coupling via ferroelastic non-180( composite function) BaTi olympic domains.
Abstract: Magnetoelectric coupling between magnetic and electrical properties presents valuable degrees of freedom for applications. The two most promising scenarios are magnetic-field sensors that could replace low-temperature superconducting quantum interference devices, and electric-write magnetic-read memory devices that combine the best of ferroelectric and magnetic random-access memory. The former scenario requires magnetically induced continuous and reversible changes in electrical polarization. These are commonly observed, but the coupling constants thus obtained are invalid for data-storage applications, where the more difficult to achieve and rarely studied magnetic response to an electric field is required. Here, we demonstrate electrically induced giant, sharp and persistent magnetic changes (up to 2.3 x 10(-7) s m(-1)) at a single epitaxial interface in ferromagnetic 40 nm La(0.67)Sr(0.33)MnO(3) films on 0.5 mm ferroelectric BaTiO(3) substrates. X-ray diffraction confirms strain coupling via ferroelastic non-180( composite function) BaTiO(3) domains. Our findings are valid over a wide range of temperatures including room temperature, and should inspire further study with single epitaxial interfaces.
686 citations
TL;DR: It is argued that epitaxial strain does not enhance the magnetization and polarization in BiFeO3 and suggests the potential for novel devices that exploit the anticipated strain-mediated magnetoelectric coupling between the two ordered ground states.
Abstract: Wang et al recently reported multiferroic behavior, with ferromagnetic and ferroelectric polarizations that are both large at room temperature, in thin strained films of BiFeO3 (BFO). Although at room temperature, bulk BFO is ferroelectric and anti-ferromagnetic , Wang et al. reported that a 70-nm film shows both an enhanced ferroelectric polarization (90 μC cm–2) and a substantial magnetization (1 μB/Fe). This remains the only report of a robust room-temperature multiferroic and suggests the potential for novel devices that exploit the anticipated strain-mediated magnetoelectric coupling between the two ordered ground states. In this Comment, we argue that epitaxial strain does not enhance the magnetization and polarization in BiFeO3
554 citations
TL;DR: In this article, the authors demonstrate that the true film capacitance of the epitaxial layers is similar to that of the electrode interface, making analysis of capacitance as a function of film thickness necessary to achieve deconvolution.
Abstract: Temperature dependent impedance spectroscopy enables the many contributions to the dielectric and resistive properties of condensed matter to be deconvoluted and characterized separately. We have achieved this for multiferroic epitaxial thin films of BiFeO_(3) (BFO) and BiMnO_(3) (BMO), key examples of materials with strong magnetoelectric coupling. We demonstrate that the true film capacitance of the epitaxial layers is similar to that of the electrode interface, making analysis of capacitance as a function of film thickness necessary to achieve deconvolution. We modeled non-Debye impedance response using Gaussian distributions of relaxation times and reveal that conventional resistivity measurements on multiferroic layers may be dominated by interface effects. Thermally activated charge transport models yielded activation energies of 0.60± 0.05 eV (BFO) and 0.25± 0.03 eV (BMO), which is consistent with conduction dominated by oxygen vacancies (BFO) and electron hopping (BMO). The intrinsic film dielectric constants were determined to be 320± 75 (BFO) and 450± 100 (BMO).
134 citations
TL;DR: In this article, a resistivity of 5×107Ωcm and an effective (i.e. thickness dependent) dielectric constant of 1400 were obtained for BiMnO3 (010) films.
Abstract: BiMnO3 (010) films (100nm) were grown epitaxially on SrTiO3 (001) and 0.2at.% Nb-doped SrTiO3 (001) substrates using pulsed laser deposition. The microstructure, electrical, and magnetic properties, and indeed the formation of the correct phase, were found to be very sensitive to growth parameters. This optimization has resulted in highly resistive BiMnO3 films and thus enabled room-temperature dielectric measurements: We obtained a resistivity of 5×107Ωcm, and an effective (i.e. thickness dependent) dielectric constant of 1400. These findings pave the way for magnetoelectric measurements and further optimization.
79 citations
Cited by
More filters
TL;DR: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements that arises through the quantum mechanical phenomenon of exchange.
Abstract: A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.
6,813 citations
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.
Abstract: Magnetism and ferroelectricity are essential to many forms of current technology, and the quest for multiferroic materials, where these two phenomena are intimately coupled, is of great technological and fundamental importance. Ferroelectricity and magnetism tend to be mutually exclusive and interact weakly with each other when they coexist. The exciting new development is the discovery that even a weak magnetoelectric interaction can lead to spectacular cross-coupling effects when it induces electric polarization in a magnetically ordered state. Such magnetic ferroelectricity, showing an unprecedented sensitivity to ap plied magnetic fields, occurs in 'frustrated magnets' with competing interactions between spins and complex magnetic orders. We summarize key experimental findings and the current theoretical understanding of these phenomena, which have great potential for tuneable multifunctional devices.
3,683 citations
TL;DR: In this paper, the authors summarize both the basic physics and unresolved aspects of BiFeO3 and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.
Abstract: BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.
3,526 citations
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.
Abstract: Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.
3,472 citations
TL;DR: In this article, a review of mostly recent activities can be found, with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972.
Abstract: Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...
3,288 citations