Multiferroics

2017 ◽  
Author(s):  
N. Nagaosa
Keyword(s):  
Spin Structure ◽  
Berry Phase ◽  
Spin Current ◽  
Electric Polarization ◽  
Constrained Systems ◽  
Gauge Fields ◽  
Spin States ◽  
Recent Developments ◽  
Electronic Configurations ◽  
Vector Spin Chirality

This chapter delves into the physics of multiferroics, the recent developments of which are discussed here from the viewpoint of the spin current and “emergent electromagnetism” for constrained systems. It presents the three sources of U(1) gauge fields, namely, the Berry phase associated with the noncollinear spin structure, the spin-orbit interaction (SOI), and the usual electromagnetic field. The chapter reviews multiferroic phenomena in noncollinear magnets from this viewpoint and discusses theories of multiferroic behavior of cycloidal helimagnets in terms of the spin current or vector spin chirality. Relativistic SOI leads to a coupling between the spin current and the electric polarization, and hence the ferroelectric and dielectric responses are a new and important probe for the spin states and their dynamical properties. Microscopic theories of the ground state polarization for various electronic configurations, collective modes including the electromagnon, and some predictions including photoinduced chirality switching are discussed with comparison to experimental results.

scholarly journals Functional THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Cormac McDonnell ◽  
Junhong Deng ◽  
Symeon Sideris ◽  
Tal Ellenbogen ◽  
Guixin Li
Keyword(s):  
Amino Acids ◽  
Linear Polarization ◽  
Berry Phase ◽  
Science And Technology ◽  
Optical Control ◽  
Biomedical Science ◽  
Spin States ◽  
Single Cycle ◽  
All Optical ◽  
Thz Waves

AbstractRecent advances in the science and technology of THz waves show promise for a wide variety of important applications in material inspection, imaging, and biomedical science amongst others. However, this promise is impeded by the lack of sufficiently functional THz emitters. Here, we introduce broadband THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces, which exhibit unique optical functionalities. Using these new emitters, we experimentally demonstrate tunable linear polarization of broadband single cycle THz pulses, the splitting of spin states and THz frequencies in the spatial domain, and the generation of few-cycle pulses with temporal polarization dispersion. Finally, we apply the ability of spin control of THz waves to demonstrate circular dichroism spectroscopy of amino acids. Altogether, we achieve nanoscale and all-optical control over the phase and polarization states of the emitted THz waves.

SPINMOTIVE FORCE IN MAGNETIC NANOSTRUCTURES

SPIN ◽  
2013 ◽  
Vol 03 (02) ◽  
pp. 1330004 ◽  
Author(s):  
JUN'ICHI IEDA ◽  
YUTA YAMANE ◽  
SADAMICHI MAEKAWA
Keyword(s):  
Energy Transfer ◽  
Spin Current ◽  
Magnetic Nanostructures ◽  
Mutual Interaction ◽  
Conduction Electrons ◽  
Recent Developments ◽  
Basic Concepts

The mutual interaction between spin current and magnetization is a key phenomenon in spintronics. This interaction leads to a spinmotive force, a mechanism of energy-transfer from magnetization into conduction electrons. In this paper, the basic concepts and recent developments of the spinmotive force are introduced.

scholarly journals Large linear magnetoelectric effect and field-induced ferromagnetism and ferroelectricity in DyCrO4

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Xudong Shen ◽  
Long Zhou ◽  
Yisheng Chai ◽  
Yan Wu ◽  
Zhehong Liu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Spin Structure ◽  
Magnetoelectric Effect ◽  
Electric Polarization ◽  
Metamagnetic Transition ◽  
Ferromagnetic Component ◽  
Antiferromagnetic Structure ◽  
Field Control ◽  
Ferromagnetic Magnetization

Abstract All the magnetoelectric properties of scheelite-type DyCrO4 are characterized by temperature- and field-dependent magnetization, specific heat, permittivity, electric polarization, and neutron diffraction measurements. Upon application of a magnetic field within ±3 T, the nonpolar collinear antiferromagnetic structure leads to a large linear magnetoelectric effect with a considerable coupling coefficient. An applied electric field can induce the converse linear magnetoelectric effect, realizing magnetic field control of ferroelectricity and electric field control of magnetism. Furthermore, a higher magnetic field (>3 T) can cause a metamagnetic transition from the initially collinear antiferromagnetic structure to a canted structure, generating a large ferromagnetic magnetization up to 7.0 μB f.u.−1. Moreover, the new spin structure can break the space inversion symmetry, yielding ferroelectric polarization, which leads to coupling of ferromagnetism and ferroelectricity with a large ferromagnetic component.

scholarly journals Skyrmions in Multiferroic Insulator

2014 ◽  
Vol 70 (a1) ◽  
pp. C1547-C1547
Author(s):  
Shinichiro Seki
Keyword(s):  
Present Finding ◽  
Berry Phase ◽  
High Energy ◽  
Electric Polarization ◽  
Orbit Interaction ◽  
Nanometer Scale ◽  
Metallic Materials ◽  
Device Applications ◽  
High Energy Efficiency ◽  
Spin Texture

Magnetic skyrmion is a topologically stable particle-like object, which appears as nanometer-scale vortex-like spin texture in a chiral-lattice magnet [1]. In metallic materials (MnSi, FeGe, Fe1-xCoxSi etc), electrons moving through skyrmion spin texture gain a nontrivial quantum Berry phase, which provides topological force to the underlying spin texture and enables the current-induced manipulation of magnetic skyrmion [2]. Such electric controllability, in addition to the particle-like nature, is a promising advantage for potential spintronic device applications. Recently, we newly discovered that skyrmions appear also in an insulating chiral-lattice magnet Cu2OSeO3 [3]. We find that the skyrmions in insulator can magnetically induce electric polarization through the relativistic spin-orbit interaction, which implies possible manipulation of the skyrmion by external electric field without loss of joule heating. The present finding of multiferroic skyrmion may pave a new route toward the engineering of novel magnetoelectric devices with high energy efficiency. In this talk, our recent attempts to drive skyrmions by external field are also introduced.

scholarly journals High Spin States in 193Hg

2020 ◽  
Vol 4 ◽  
pp. 170
Author(s):  
N. Fotiades ◽  
Et al.
Keyword(s):  
Excited States ◽  
High Spin ◽  
Normal Level ◽  
Beam Energy ◽  
Spin Structure ◽  
Spin States ◽  
Tandem Accelerator ◽  
High Spin States ◽  
Γ Rays ◽  
Γ Ray

The high-spin structure of 193Hg was investigated by in-beam γ-ray spectro­scopic techniques. The tandem accelerator at Daresbury Laboratory, U. K., was used to populate excited states of 193Hg through the reaction 150Nd(48Ca,5n)193Hg at a beam energy of 213 MeV and the EUROGAM detector array was used to de­ tect the γ-rays emitted by the deexciting nuclei. The normal level scheme has been further extended and a new band has been observed. In addition two new ΔI=1 structures of competing dipole and quadrupole transitions were found which will be discussed in detail.

High spin states in 96Tc populated through the (α,n) reaction

1980 ◽  
Vol 58 (2) ◽  
pp. 174-190 ◽  
Author(s):  
H. A. Mach ◽  
M. W. Johns ◽  
J. V. Thompson
Keyword(s):  
Theoretical Model ◽  
High Spin ◽  
Spin Structure ◽  
Gamma Ray ◽  
Angular Distributions ◽  
Spin States ◽  
High Spin States ◽  
Gamma Coincidence ◽  
Electron Conversion ◽  
Conversion Coefficients

High spin states of 96Tc populated by the (α,n) reaction using alpha beams from 13 to 27 MeV have been studied. Gamma-ray energies and intensities, gamma–gamma coincidence probabilities, gamma-ray angular distributions, and electron conversion coefficients were determined at 18 MeV. In addition, some results taken at 14 MeV are reported.The high spin structure observed in this work includes the following levels: 49.3(6+), 318.8(6+), 574.7(7+), 926.9(9+), 946.5(8+), 1062.1(8+), 1138.8(8+), 1447.2(9+), 1702.8(10+), 1861.6(9+), 1922.3(11+), 2147.5(11+), 2213.5(10(+)), 2317.2(12+), 2396.8(11(+)), 2599.0((13)+), 2642.4((14)+), and 3020.1(12(+)).These experiments also clarify and extend the information obtained by previous workers. In particular, evidence is adduced for low-lying states at 0.0(7+), 34.3(4+), 45.3(5+), 120.3(3−), 177.0(5+), 226.2(2−), 227.0(4+), and 254.3(3+).The work identifies many other states of intermediate energy.Attenuation coefficients for states in 96Tc are calculated using a theoretical model.

Octahedral aromaticity in 2S+1A1g X6q clusters (X = Li–C and Be–Si, S = 0–3, and q = −2 to +4)

2016 ◽  
Vol 18 (17) ◽  
pp. 11700-11706 ◽  
Author(s):  
Ouissam El Bakouri ◽  
Miquel Duran ◽  
Jordi Poater ◽  
Ferran Feixas ◽  
Miquel Solà
Keyword(s):  
Spin States ◽  
Open Shells ◽  
Electronic Configurations ◽  
Closed Shells

Octahedral aromaticity was found in most clusters of formula X6q (X = Li–C and Be–Si) with q = −2 to +4 and spin states ranging from the singlet to the septet that have electronic configurations of closed-shells or open shells half-filled with the same spin electrons.

GAUGE-INVARIANT QUANTISATION OF CHIRAL GAUGE THEORIES

1990 ◽  
Vol 05 (03) ◽  
pp. 175-182 ◽  
Author(s):  
T. D. KIEU
Keyword(s):  
Path Integral ◽  
Gauge Theories ◽  
Berry Phase ◽  
Integral Functional ◽  
Gauge Fields ◽  
Quantum Mechanical ◽  
Gauge Invariant ◽  
Normal Ordering ◽  
Schwinger Model ◽  
Holomorphic Representation

The path-integral functional of chiral gauge theories with background gauge potentials are derived in the holomorphic representation. Justification is provided, from first quantum mechanical principles, for the appearance of a functional phase factor of the gauge fields in order to maintain the gauge invariance. This term is shown to originate either from the Berry phase of the first-quantized hamiltonians or from the normal ordering of the second-quantized hamiltonian with respect to the Dirac in-vacuum. The quantization of the chiral Schwinger model is taken as an example.

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