Showing papers by "Michel Viret published in 2007"
TL;DR: In this paper, it was shown that the room-temperature ferroelectricity in solid solutions of a single crystal of the material is found to have a large spontaneous electric polarization.
Abstract: From an experimental point of view, room-temperature ferroelectricity in $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ is raising many questions. Electric measurements made a long time ago on solid solutions of $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ with $\mathrm{Pb}(\mathrm{Ti},\mathrm{Zr}){\mathrm{O}}_{3}$ indicate that a spontaneous electric polarization exists in $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ below the Curie temperature ${T}_{C}=1143\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Yet in most reported works, the synthesized samples are too conductive at room temperature to get a clear polarization loop in the bulk without any effects of extrinsic physical or chemical parameters. Surprisingly, up to now there has been no report of a $P(E)$ (polarization versus electric field) loop at room temperature on single crystals of $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$. We describe here our procedure to synthesize ceramics and to grow good quality sizeable single crystals by a flux method. We demonstrate that $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ is indeed ferroelectric at room temperature through evidence by piezoresponse force microscopy and $P(E)$ loops. The polarization is found to be large, around $60\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{C}∕{\mathrm{cm}}^{2}$, a value that has only been reached in thin films. Magnetic measurements using a superconducting quantum interference device magnetometer and M\"ossbauer spectroscopy are also presented. The latter confirms the results of nuclear magnetic resonance measurements concerning the anisotropy of the hyperfine field attributed to the magnetic cycloidal structure.
609 citations
TL;DR: In this article, electric polarization loops are measured at room temperature on highly pure BiFeO3 single crystals synthesized by a flux growth method, and the resulting low leakage currents allow the authors to measure a large spontaneous polarization in excess of 100μCcm−2.
Abstract: Electric polarization loops are measured at room temperature on highly pure BiFeO3 single crystals synthesized by a flux growth method. Because the crystals have a high electrical resistivity, the resulting low leakage currents allow the authors to measure a large spontaneous polarization in excess of 100μCcm−2, a value never reported in the bulk. During electric cycling, the slow degradation of the material leads to an evolution of the hysteresis curves eventually preventing full saturation of the crystals.
565 citations
TL;DR: In this paper, electric polarization loops are measured at room temperature on highly pure BiFeO3 single crystals synthesized by a flux growth method, and the resulting low leakage currents allow them to measure a large spontaneous polarization reaching 100 microC.
Abstract: Electric polarization loops are measured at room temperature on highly pure BiFeO3 single crystals synthesized by a flux growth method. Because the crystals have a high electrical resistivity, the resulting low leakage currents allow us to measure a large spontaneous polarization reaching 100 microC.cm^{-2}, a value never reported in the bulk. During electric cycling, the slow degradation of the material leads to an evolution of the hysteresis curves eventually preventing full saturation of the crystals.
57 citations
TL;DR: In this article, the effective spin pressure induced by an electric current on a domain wall in a ferromagnet is determined using a simple classical model, which allows us to extend previous theories to arbitrary domain-wall widths.
Abstract: The effective spin pressure induced by an electric current on a domain wall in a ferromagnet is determined using a simple classical model, which allows us to extend previous theories to arbitrary domain-wall widths. In particular, the role of spatially nonuniform components of the torques are analyzed in detail. We find that in the steady state, the main effect of the current is a distortion of the wall, which should enhance depinning. We also discuss the nonadiabatic part of the torque and find that this term, responsible for the pressure on the wall, depends on the nature of spin-flip scattering events.
54 citations
TL;DR: In this article, the association of multi-energy ion implantation with magnetic and structural analysis methods, particularly X-ray diffraction reciprocal space maps (XRD RSM), is shown to give new original information about the microstructure of Fe-implanted SiC, a good candidate for diluted magnetic semiconductors (DMS) applications.
Abstract: Association of multi-energy ion implantation with magnetic and structural analysis methods, particularly X-ray diffraction reciprocal space maps (XRD RSM), is shown to be able to give new original information about the microstructure of Fe-implanted SiC, a good candidate for diluted magnetic semiconductors (DMS) applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
7 citations
TL;DR: In this paper, the ferromagnetic resonance spectra of individual micron size disks with identical diameter, 1μm, but different layer structures were compared using a magnetic resonance force microscope.
Abstract: Using a magnetic resonance force microscope, we compare the ferromagnetic resonance spectra of individual micron size disks with identical diameter, 1μm, but different layer structures. For a disk composed of a single 43.3-nm-thick Permalloy (Py) layer, the lowest energy mode in the perpendicular configuration is the uniform precession. The higher energy modes are standing spin waves confined along the diameter of the disk. For a Cu (30nm)∕Py (100nm)∕Cu (30nm) multilayer structure, it has been interpreted that the lowest energy mode becomes a precession localized at the Cu/Py interfaces. When the multilayer is changed to Py (100nm)∕Cu (10nm)∕Py (10nm), this localized mode of the thick layer becomes coupled to the precession of the thin layer.
2 citations