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Taka-hisa Arima

Bio: Taka-hisa Arima is an academic researcher from University of Tokyo. The author has contributed to research in topics: Magnetization & Magnetic field. The author has an hindex of 67, co-authored 426 publications receiving 25692 citations. Previous affiliations of Taka-hisa Arima include Global Alliance in Management Education & Tohoku University.


Papers
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Journal ArticleDOI
06 Nov 2003-Nature
TL;DR: The discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering and gigantic magnetoelectric and magnetocapacitance effects are found.
Abstract: The magnetoelectric effect--the induction of magnetization by means of an electric field and induction of polarization by means of a magnetic field--was first presumed to exist by Pierre Curie, and subsequently attracted a great deal of interest in the 1960s and 1970s (refs 2-4). More recently, related studies on magnetic ferroelectrics have signalled a revival of interest in this phenomenon. From a technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate materials is limited and the effects are typically too small to be useful in applications. Here we report the discovery of ferroelectricity in a perovskite manganite, TbMnO3, where the effect of spin frustration causes sinusoidal antiferromagnetic ordering. The modulated magnetic structure is accompanied by a magnetoelastically induced lattice modulation, and with the emergence of a spontaneous polarization. In the magnetic ferroelectric TbMnO3, we found gigantic magnetoelectric and magnetocapacitance effects, which can be attributed to switching of the electric polarization induced by magnetic fields. Frustrated spin systems therefore provide a new area to search for magnetoelectric media.

3,769 citations

Journal ArticleDOI
TL;DR: Insulator-metal phenomena depending on band filling, temperature, and external magnetic field have been investigated for prototypical double-exchange ferromagnets, namely, crystals of crystals of La 1-x, showing large negative magnetoresistance around the ferromagnetic transition temperature.
Abstract: Insulator-metal phenomena depending on band filling (doping degree), temperature, and external magnetic field have been investigated for prototypical double-exchange ferromagnets, namely, crystals of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ (0\ensuremath{\le}x\ensuremath{\le}0.6). The electronic phase diagram in the plane of the temperature vs nominal hole concentration (x) has been deduced from the magnetic and electrical measurements on the melt-grown crystals. Around the ferromagnetic transition temperature ${\mathit{T}}_{\mathit{C}}$, large negative magnetoresistance was observed. Irrespective of temperature, reduction of the resistivity is scaled with the field-induced magnetization (M) as -\ensuremath{\Delta}\ensuremath{\rho}/\ensuremath{\rho}=C(M/${\mathit{M}}_{\mathit{s}}$${)}^{2}$ for M/${\mathit{M}}_{\mathit{s}}$\ensuremath{\lesssim}0.3, where ${\mathit{M}}_{\mathit{s}}$ is the saturated magnetization. The coefficient C strongly depends on x, i.e., C\ensuremath{\approxeq}4 near the compositional insulator-metal phase boundary (${\mathit{x}}_{\mathit{c}}$\ensuremath{\sim}0.17), but decreases down to \ensuremath{\approxeq}1 for xg=0.4, indicating the critical change of the electronic state.

2,412 citations

Journal ArticleDOI
06 Mar 2009-Science
TL;DR: In this paper, the relative phases of constituent atomic orbitals in an electronic wave function were used to probe the Mott insulating state induced by relativistic spin-orbit coupling in the layered 5d transition metal oxide Sr2IrO4.
Abstract: Measurement of the quantum-mechanical phase in quantum matter provides the most direct manifestation of the underlying abstract physics. We used resonant x-ray scattering to probe the relative phases of constituent atomic orbitals in an electronic wave function, which uncovers the unconventional Mott insulating state induced by relativistic spin-orbit coupling in the layered 5d transition metal oxide Sr2IrO4. A selection rule based on intra-atomic interference effects establishes a complex spin-orbital state represented by an effective total angular momentum = 1/2 quantum number, the phase of which can lead to a quantum topological state of matter.

863 citations

Journal ArticleDOI
TL;DR: The resulting spectrum in the high-{ital T}{sub {ital c}} regime is suggestive of a strongly itinerant character of the state in the moderately doped CuO{sub 2} plane while appreciable weight remains in the charge-transfer energy region.
Abstract: Optical reflectivity spectra are studied for single crystals of the prototypical high-${\mathit{T}}_{\mathit{c}}$ system ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ over a wide compositional range 0\ensuremath{\le}x\ensuremath{\le}0.34, which covers insulating, superconducting, and normal metallic phases. The measurements are made at room temperature over an energy range from 0.004 to 35 eV for the polarization parallel to the ${\mathrm{CuO}}_{2}$ planes. They are also extended to the perpendicular polarization to study anisotropy and to discriminate the contribution from the ${\mathrm{CuO}}_{2}$ plane. The present study focuses on the x dependence of the optical spectrum, which makes it possible to sort out the features of the excitations in the ${\mathrm{CuO}}_{2}$ plane and thus to characterize the electronic structure of the ${\mathrm{CuO}}_{2}$ plane in the respective phase. Upon doping into the parent insulator ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ with a charge-transfer energy gap of about 2 eV the spectral weight is rapidly transferred from the charge-transfer excitation to low-energy excitations below 1.5 eV. The low-energy spectrum is apparently composed of two contributions; a Drude-type one peaked at \ensuremath{\omega}=0 and a broad continuum centered in the midinfrared range. The high-${\mathit{T}}_{\mathit{c}}$ superconductivity is realized as doping proceeds and when the transfer of the spectrum weight is saturated. The resulting spectrum in the high-${\mathit{T}}_{\mathit{c}}$ regime is suggestive of a strongly itinerant character of the state in the moderately doped ${\mathrm{CuO}}_{2}$ plane while appreciable weight remains in the charge-transfer energy region. The spectrum exhibits a second drastic change for heavy doping (x\ensuremath{\sim}0.25) corresponding to the superconductor-to-normal-metal transition and becomes close to that of a Fermi liquid. The results are universal for all the known cuprate superconductors including the electron-doped compounds, and they reconcile the dc transport properties with the high-energy spectroscopic results.

672 citations

Journal ArticleDOI
TL;DR: Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K, indicating the clamping of the ferromagnetic and ferroelectric domain walls.
Abstract: Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K. The direction [110] of the spontaneous polarization is normal to both the magnetization easy axis [001] and to the propagation axis [110] of the transverse spiral component, in accord with the prediction based on the spin-current model. The reversal of the spontaneous magnetization by a small magnetic field (approximately 0.1 T) induces the reversal of the spontaneous polarization, indicating the clamping of the ferromagnetic and ferroelectric domain walls.

591 citations


Cited by
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Journal ArticleDOI
17 Aug 2006-Nature
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

Journal ArticleDOI
TL;DR: The dynamical mean field theory of strongly correlated electron systems is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition.
Abstract: We review the dynamical mean-field theory of strongly correlated electron systems which is based on a mapping of lattice models onto quantum impurity models subject to a self-consistency condition. This mapping is exact for models of correlated electrons in the limit of large lattice coordination (or infinite spatial dimensions). It extends the standard mean-field construction from classical statistical mechanics to quantum problems. We discuss the physical ideas underlying this theory and its mathematical derivation. Various analytic and numerical techniques that have been developed recently in order to analyze and solve the dynamical mean-field equations are reviewed and compared to each other. The method can be used for the determination of phase diagrams (by comparing the stability of various types of long-range order), and the calculation of thermodynamic properties, one-particle Green's functions, and response functions. We review in detail the recent progress in understanding the Hubbard model and the Mott metal-insulator transition within this approach, including some comparison to experiments on three-dimensional transition-metal oxides. We present an overview of the rapidly developing field of applications of this method to other systems. The present limitations of the approach, and possible extensions of the formalism are finally discussed. Computer programs for the numerical implementation of this method are also provided with this article.

5,230 citations

Journal Article
TL;DR: The first direct detection of gravitational waves and the first observation of a binary black hole merger were reported in this paper, with a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ.
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

4,375 citations