scholarly journals Spherical neutron polarimetry in multiferroics under external stimuli

2014 ◽  
Vol 70 (a1) ◽  
pp. C151-C151
Author(s):  
Vladimir Hutanu ◽  
Andrew Sazonov ◽  
Georg Roth ◽  
In-Hwan Oh ◽  
Max Baum ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Structure ◽  
Magnetic Order ◽  
Strong Electric Field ◽  
Electric Polarization ◽  
Square Lattice ◽  
Microscopic Mechanism ◽  
Coupling Energy ◽  
Neutron Polarimetry

Study of multiferroics, materials simultaneously having more than one primary ferroic order parameter, is a hot topic of material sciences. The most extensively studied class of these compounds is the family of magnetoelectric multiferroics, where ferroelectricity can be induced by various types of magnetic orderings via the relativistic spin-orbit interaction. As a consequence of the cross coupling between spins and electric polarization, the spectacular control of the ferroelectric polarization by external magnetic field and the manipulation of the magnetic order via electric field can often be realized in these systems. Depending on the symmetry and microscopic mechanism of the multiferroicity the coupling energy between magnetic and electric ordering parameters can significantly vary. Classical neutron diffraction often fails in the precise determining of the complex magnetic structure in the multiferroics due to the presence of the statistically distributed domains in the macroscopic sample. Using spherical neutron polarimetry (SNP), known also as 3D polarization analysis, it is possible not only to precisely determine the complex magnetic structure, but also to investigate in-situ its evolution with external parameters and to control the magnetic domains distribution under the influence of the external electric or/and magnetic field. Here we will present some SNP results on few different multiferroic materials. In some of them, e.g. square lattice 2D antiferromagnet Ba2CoGe2O7, even strong electric field does not change the magnetic order. However rater week magnetic field is sufficient to create a mono-domain structure and to rotate spins in the plane. In other e.g. incommensurate (spiral) magnetic structure of the TbMnO3, solely electric field is sufficient to fully control the chirality of the magnetic structure. In the case of Cr2O3 both electric and magnetic fields should be applied in parallel in order to switch between the different antiferromagnetic domains.

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 Unusual magnetoelectric effect in paramagnetic rare-earth langasite

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Lukas Weymann ◽  
Lorenz Bergen ◽  
Thomas Kain ◽  
Anna Pimenov ◽  
Alexey Shuvaev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Rare Earth ◽  
Electric Field ◽  
Field Vector ◽  
Electric Polarization ◽  
Rare Earth Ions ◽  
Spontaneous Breaking ◽  
Unusual Behavior ◽  
Propagation Of Light ◽  
The Magnetic Field

Abstract Violation of time reversal and spatial inversion symmetries has profound consequences for elementary particles and cosmology. Spontaneous breaking of these symmetries at phase transitions gives rise to unconventional physical phenomena in condensed matter systems, such as ferroelectricity induced by magnetic spirals, electromagnons, non-reciprocal propagation of light and spin waves, and the linear magnetoelectric (ME) effect—the electric polarization proportional to the applied magnetic field and the magnetization induced by the electric field. Here, we report the experimental study of the holmium-doped langasite, HoxLa3−xGa5SiO14, showing a puzzling combination of linear and highly non-linear ME responses in the disordered paramagnetic state: its electric polarization grows linearly with the magnetic field but oscillates many times upon rotation of the magnetic field vector. We propose a simple phenomenological Hamiltonian describing this unusual behavior and derive it microscopically using the coupling of magnetic multipoles of the rare-earth ions to the electric field.

scholarly journals FRB coherent emission from decay of Alfvén waves

2020 ◽  
Vol 494 (2) ◽  
pp. 2385-2395 ◽  
Author(s):  
Pawan Kumar ◽  
Željka Bošnjak
Keyword(s):  
Magnetic Field ◽  
Wave Packet ◽  
Electric Field ◽  
Static Magnetic Field ◽  
Strong Electric Field ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Radio Waves ◽  
Electron Positron

ABSTRACT We present a model for fast radio bursts (FRBs) where a large-amplitude Alfvén wave packet is launched by a disturbance near the surface of a magnetar, and a substantial fraction of the wave energy is converted to coherent radio waves at a distance of a few tens of neutron star radii. The wave amplitude at the magnetar surface should be about 1011 G in order to produce an FRB of isotropic luminosity 1044 erg s−1. An electric current along the static magnetic field is required by Alfvén waves with non-zero component of transverse wave vector. The current is supplied by counter-streaming electron–positron pairs, which have to move at nearly the speed of light at larger radii as the plasma density decreases with distance from the magnetar surface. The counter-streaming pairs are subject to two-stream instability, which leads to formation of particle bunches of size of the order of c/ωp, where ωp is the plasma frequency. A strong electric field develops along the static magnetic field when the wave packet arrives at a radius where electron–positron density is insufficient to supply the current required by the wave. The electric field accelerates particle bunches along the curved magnetic field lines, and that produces the coherent FRB radiation. We provide a number of predictions of this model.

Identities between reflexion and transmission coefficients and electric field components for certain anisotropic modes of oblique propagation

1971 ◽  
Vol 6 (2) ◽  
pp. 257-270 ◽  
Author(s):  
J. Heading
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Differential Equations ◽  
Electric Field ◽  
Electromagnetic Waves ◽  
Electric Polarization ◽  
Stratified Medium ◽  
Transmission Coefficients ◽  
Oblique Propagation ◽  
Integral Identities

A wide-ranging investigation is rendered possible by a judicious combination of products of electric field components and electric polarization components for two distinct modes of propagation of electromagnetic waves in an anisotropic, ionized, stratified medium. The differential equations, governing oblique propagation in these two distinct modes in such a medium, are combined to yield various integral identities when integrated throughout the medium. These lead to a large number of relations between the reflexion and transmission coefficients (for incidence from below and from above) and the fields throughout the medium, each containing as a factor just one of the components of the external magnetic field pervading the medium.

A Magnetoelectric Effect in Low-Carrier Density Colossal Magnetoresistance Materials

2006 ◽  
Vol 52 ◽  
pp. 21-26
Author(s):  
M. Auslender
Keyword(s):  
Magnetic Field ◽  
Solid State ◽  
Electric Field ◽  
Acoustic Waves ◽  
Carrier Density ◽  
Colossal Magnetoresistance ◽  
Magnetoelectric Effect ◽  
Strong Electric Field ◽  
Acoustoelectric Effect ◽  
Dc Electric Field

It is shown that in colossal magnetoresistance materials an inhomogeneous alternating magnetic field generates a strong electric field of non-inductive nature. This magnetoelectric effect is an analog of acoustoelectric effect in conventional semiconductors. Due to the above electric field spin waves in the former materials, like acoustic waves in the latter ones, acquire an additional attenuation at equilibrium. This attenuation may be converted to amplification by applying strong enough dc electric field drifting the carriers (solid-state Cherenkov’s effect). The experiments, which probed this phenomenon in HgCr2Se4 using spin wave pumping, are discussed.

Magnetic Structure of Nanosized Ferrimagnetic Particle Depending on External Parameters

2014 ◽  
Vol 1040 ◽  
pp. 70-73 ◽  
Author(s):  
V.A. Rodionov ◽  
E.P. Naiden
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Magnetic Structure ◽  
Magnetic Order ◽  
Magnetocrystalline Anisotropy

In this work we performed analysis of the magnetic order of nanosized ferrimagnetic particle at the temperature and magnetic field changes, using Monte-Carlo method. The calculations take into account real mechanisms of exchange and magnetocrystalline anisotropy of ferrospinels.

The Influence of the Magnetic Field on Electrically Induced Domain Wall Motion

2015 ◽  
Vol 233-234 ◽  
pp. 443-446 ◽  
Author(s):  
D.A. Sechin ◽  
E.P. Nikolaeva ◽  
A.P. Pyatakov ◽  
A.B. Nikolaev ◽  
T.B. Kosykh
Keyword(s):  
Magnetic Field ◽  
Domain Wall ◽  
Electric Field ◽  
Wall Motion ◽  
Domain Walls ◽  
Domain Wall Motion ◽  
Electric Polarization ◽  
Measured Velocity ◽  
Iron Garnet ◽  
The Magnetic Field

Domain walls in iron garnet films demonstrate magnetoelectric properties that manifest themselves as a displacement induced by inhomogeneous electric field. In this paper the results of the study of electric field induced domain wall dynamics and its dependence on external magnetic field are presented. The measured velocity of the electrically induced domain wall motion increased by an order with the magnetic field applied perpendicular to the domain wall plane. The numerical simulation shows that the observed behaviour of the domain wall can be explained by magnetic field induced modification of its internal micromagnetic structure and enhancement of the electric polarization associated with the wall.

scholarly journals Full electric-field tuning of the nonreciprocal transport effect in massive chiral fermions with trigonal warping

2021 ◽  
Author(s):  
Wei-Li Lee ◽  
Elisha Cho-Hao Lu ◽  
Liang Li ◽  
Cheng-Tung Cheng
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electric Polarization ◽  
Transport Effect ◽  
Nonreciprocal Effect ◽  
Lifshitz Transition ◽  
Valley Polarization ◽  
Trigonal Warping ◽  
A Current ◽  
Exact Cancellation

Abstract In a noncentrosymmetric system, an intrinsic electric polarization is allowed and may lead to unusual nonreciprocal charge transport phenomena. As a result, a current-dependent resistance, arising from the magnetoelectric anisotropy term of k · E × B, appears and acts as a current rectifier with the amount of rectification being linearly proportional to the magnitude of both current and applied magnetic field. In this work, a different type of nonreciprocal transport effect was demonstrated in a graphene-based device, which requires no external magnetic field. Owing to the unique pseudospin (valley) degree of freedom in chiral fermions with trigonal warping, a large nonreciprocal transport effect was uncovered in a gapped bilayer graphene, where electric-field tunabilities of the band gap and valley polarization play an important role. The exact cancellation of nonreciprocal effect between two different valleys is effectively removed by breaking the inversion symmetry via electric gatings. The magnitude of the current rectification appears to be at a maximum when the Fermi surface undergoes a Lifshitz transition near the band edges, which is proportional to the current and the displacement field strength. The full electric-field tuning of the nonreciprocal transport effect without a magnetic field opens up a new direction for valleytronics in two-dimensional based devices.

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