Dynamic Magnetoelectric Effect Research Articles

Nonreciprocal Directional Dichroism and Toroidalmagnons in Helical Magnets

We investigate a dynamical magnetoelectric effect due to a magnetic resonance in helical spin structures through the coupling between magnetization and electric polarization via a spin current mechanism. We show that the magnon has both the dynamical magnetic moment $\Delta M^\omega$ and the electric moment $\Delta P^\omega$ ($\perp \Delta M^\omega$), i.e., a dynamical toroidal moment, under external magnetic fields, and thus it is named the {\em toroidalmagnon}. The toroidalmagnon exists in most conical spin structures owing to the generality of the spin current mechanism. In the absorption of electromagnetic waves, the toroidalmagnon excitation process generally induces a nonreciprocal directional dichroism as a consequence of an interference of the magnetic and electric responses.

Dynamical magnetoelectric effects in multiferroic oxides

Multiferroics with coexistent ferroelectric and magnetic orders can provide an interesting laboratory to test unprecedented magnetoelectric (ME) responses and their possible applications. One such example is the dynamical and/or resonant coupling between magnetic and electric dipoles in a solid. As examples of such dynamical ME effects, (i)the multiferroic domain wall dynamics and (ii)the electric dipole active magnetic responses are discussed with an overview of recent experimental observations.

Optical Response of Relativistic Electrons in the Polar BiTeI Semiconductor

The transitions between the spin-split bands by spin-orbit interaction are relevant to many novel phenomena such as the resonant dynamical magnetoelectric effect and the spin Hall effect. We perform optical spectroscopy measurements combined with first-principles calculations to study these transitions in the recently discovered giant bulk Rashba spin-splitting system BiTeI. Several novel features are observed in the optical spectra of the material including a sharp edge singularity due to the reduced dimensionality of the joint density of states and a systematic doping dependence of the intraband transitions between the Rashba-split branches. These confirm the bulk nature of the Rashba-type splitting in BiTeI and manifest the relativistic nature of the electron dynamics in a solid.

Magnetoelectricity in the ferrimagnetic Cu2OSeO3: symmetry analysis and Raman scattering study

sublattices ferrimagnet Cu2OSeO3 with a cubic symmetry and a linear magnetoelectric effect. There is no spectroscopic evidence for structural lattice distortions below TC=60K, which are expected due to magnetoelectric coupling. Using symmetry arguments we explain this observation by considering a special type of ferrimagnetic ground state which does not generate a spontaneous electric polarization. Interestingly, Raman scattering shows a strong increase of electric polarization of media through a dynamic magnetoelectric effect as a remarkable enhancement of the scattering intensity below TC. New lines of purely magnetic origin have been detected in the magnetically ordered state. A part of them are attributed as scattering on exchange magnons. Using this observation and further symmetry considerations we argue for strong Dzyaloshinskii–Moriya interaction existing in the Cu2OSeO3.

Dynamic investigations of multiferroics: Terahertz and beyond

We overview our recent studies of the electrodynamic response of multiferroic compounds. We report results of magnetic dynamics in multiferroic hexagonal manganite HoMnO3 by far-infrared spectroscopy in a magnetic field. Our results provide insight into the ferromagnetic nature of the rare-earth/Mn exchange that enables the electric-field control of magnetism in HoMnO3. In the multiferroic Ba0.6Sr1.4Zn2Fe12O22 we have observed a magnetic resonance using time domain pump-probe reflectance spectroscopy revealing the importance of the dynamic magnetoelectric effect which is a modulation of the dielectric tensor by magnetization precession. Our results highlight that magneto-electric dynamics manifest from the far-infrared through the visible and that both time-integrated and time-resolved spectroscopy are important tools in elucidating the microscopic properties of multiferroics.

Detection of Coherent Magnons via Ultrafast Pump-Probe Reflectance Spectroscopy in MultiferroicBa0.6Sr1.4Zn2Fe12O22

We report the detection of a magnetic resonance mode in multiferroic Ba0.6Sr1.4Zn2Fe12O22 using time-domain pump-probe reflectance spectroscopy. Magnetic sublattice precession is coherently excited via picosecond thermal modification of the exchange energy. Importantly, this precession is recorded as a change in reflectance caused by the dynamic magnetoelectric effect. Thus, transient reflectance provides a sensitive probe of magnetization dynamics in materials with strong magnetoelectric coupling, such as multiferroics, revealing new possibilities for application in spintronics and ultrafast manipulation of magnetic moments.

Dynamic magnetoelectric effect in terbium molybdate

The electric polarization induced in ferroelectric terbium molybdate by a magnetic field linearly varying with time is measured. The measurements are performed in fields up to 19 T at different specified rates of change in the magnetic field at temperatures of 273 and 219 K. The results obtained indicate that there are magnetoelectric effects of two types. One of them is a conventional magnetoelectric effect, which is appropriately referred to as the static magnetoelectric effect. The other effect is characterized by the fact that the electric polarization increases with an increase in the rate of change in the magnetic field and relaxes with time to zero at a fixed nonzero field. This phenomenon is termed the dynamic magnetoelectric effect.

Magneto-electric coupling in piezoelectric–piezomagnetic superlattices

Abstract A piezoelectric–piezomagnetic superlattice (PPS) is proposed to present the magneto-electric (ME) coupling wherein electric polarization induces magnetization or vice versa through the layer's coherent strain. We reveal that in PPS, the interaction of electromagnetic waves with the correspondent alternative piezoelectric and piezomagnetic superlattices through their vibrations excites the piezoelectric and the piezomagnetic phonon polaritons simultaneously. The polaritons couple with each other to give rise to a stop band, in which double negative permittivity and permeability can be realized, however negative refraction could not occur. The coupling also results in the huge dynamic ME effect which attributes to the large ME voltage coefficient in a BaTiO3–CoFe2O4 superlattice as large as 14.9 V cm−1 Oe−1.

Dynamic magnetoelectric effect in polymer-based laminate composite

The magnetoelectric (ME) effect is defined as an induced electric polarization in a material upon applying a magnetic field, or as an induced magnetization in a material upon applying an electric field. Such effect facilitates the conversion between energies stored in magnetic and electric fields. A new kind of ME laminated composites composed with 1–3 piezoelectric PZT/epoxy composite and pseudo-1-3 magnetostrictive Terfenol-D/epoxy composite was prepared in this paper. The dynamic coupled magnetic–mechanical–electric effect in such new composites was predicted using a simple method of equivalent circuit approach, and the results were proved valuable by our experimental data. The calculation results showed good agreement to the experimental data. Both data proved that the magnetoelectric coefficient is strongly dependent not only on the volume fraction of the PZT and Terfenol-D, but also on dc magnetic field. The results testify that the resonance frequency is affected simultaneously by the dc magnetic field and the volume fraction of the PZT and Terfenol-D. For such new type of ME composites, the quantitative relationship between ME coefficient with impact factors including materials, structure and field parameters were presented in theory for the first time through equivalent circuit approach.

Field-induced anomalies of the polariton spectrum of a bounded crystal with spatial dispersion: II. Crystal plate

Conditions are determined under which an external magnetic field leads to anomalies in the spectrum of bulk TM polaritons in a crystal plate possessing simultaneously the dynamic magnetoelectric effect and spatial dispersion.

An experimental setup for dynamic measurement of magnetoelectric effect

An experimental setup is developed for the measurement of dynamic magnetoelectric effect (ME) in polycrystalline materials, using a time varying DC magnetic field on which an AC magnetic field is superimposed. The experimental data on ME on Bi5FeTi3O15 and a solid solution of (90%)BiFeO3-(10%)BaTiO3 are obtained using this setup. The linear and higher order ME coefficients can be evaluated from the output voltage. The temperature variation of ME data gives additional information corroborating with the data on magnetization.