Electrically active magnetic excitations in antiferromagnets (Review Article)

Krivoruchko, V. N.

doi:10.1063/1.4752093

Cited by 18 publications

(18 citation statements)

References 74 publications

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“…20,22, this form of boundary conditions leaves questions with regard to the microscopic interpretation of the exchange coupling constant * AB A . So, either the natural boundary conditions (8)(9) or the generalized Barnaś-Mills boundary conditions (36)(37) should be used instead.…”

Section: Discussionmentioning

confidence: 99%

“…It is easy to see that the direction of the magnetization becomes continuous if one neglects in equation (16) terms of the order of  a a x     m , where λ is the spin wave wavelength 24 (or any alternative appropriate quantity describing the characteristic length scale of the non-uniformity of the magnetization direction). This assumption (that the spin wave wavelength is greater than lattice constants of constituent materials) is the essence of the continuous medium approximation in magnonics, in which the natural boundary conditions (8)(9) are derived. In particular, this explains why such a continuous medium approach as the plane wave method 70,[74][75][76][77] is consistent with the natural boundary conditions (8-9) but experiences difficulties adopting the notion of the interlayer exchange coupling.…”

Section: Natural Hoffmann and Barnaś-mills Forms Of Magnetizatimentioning

confidence: 99%

“…Once again, equation (18) demonstrate that the terms neglected in the natural boundary conditions (8)(9) are of the order of  a  . So, the omission of the terms in the natural boundary conditions is perfectly consistent with the continuous medium approximation, while applying the Hoffmann boundary conditions to functions defined in the one and same point 71 is not.…”

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confidence: 99%

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Magnetization boundary conditions at a ferromagnetic interface of finite thickness

Kruglyak

Gorobets

et al. 2014

J. Phys.: Condens. Matter

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We develop a systematic approach by which to derive boundary conditions at an interface between two ferromagnetic materials in the continuous medium approximation. The approach treats the interface as a two-sublattice material, although the final equations connect magnetizations outside of the interface and therefore do not explicitly depend on its structure. Instead, the boundary conditions are defined in terms of some average properties of the interface, which may also have a finite thickness. In addition to the interface anisotropy and symmetric exchange coupling, this approach allows us to take into account coupling resulting from inversion symmetry breaking in the vicinity of the interface, such as the Dzyaloshinskii-Moriya antisymmetric exchange interaction. In the case of negligible interface anisotropy and Dzyaloshinskii-Moriya exchange parameters, the derived boundary conditions represent a generalization of those proposed earlier by Barnaś and Mills and are therefore named "generalized Barnaś-Mills boundary conditions". We demonstrate how one could use the boundary conditions to extract parameters of the interface via fitting of appropriate experimental data. The developed theory could be applied to modeling of both linear and non-linear spin waves, including exchange, dipole-exchange, magnetostatic, and retarded modes, as well as to calculations of nonuniform equilibrium micromagnetic configurations near the interface, with a direct impact on the research in magnonics and micromagnetism. * Corresponding author: V.V.Kruglyak@exeter.ac.uk 2

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Section: Discussionmentioning

confidence: 99%

Section: Natural Hoffmann and Barnaś-mills Forms Of Magnetizatimentioning

confidence: 99%

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confidence: 99%

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Magnetization boundary conditions at a ferromagnetic interface of finite thickness

Kruglyak

Gorobets

et al. 2014

J. Phys.: Condens. Matter

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“…In contrast, the dynamic response under oscillating fields can elucidate other significant interactions. Magnetoelectric coupling creates a new quasiparticle excitation-the electromagnon-at terahertz (THz) frequencies [7][8][9][10][11][12][13] . Electromagnons have been discovered in rareearth-doped compounds such as RMnO 3 and RMn 2 O 5 at low temperature (o70 K), and are thought to result from modifications of the Heisenberg exchange interaction 14,15 , which has a S i Á S j term in the spin Hamiltonian.…”

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confidence: 99%

High-temperature electromagnons in the magnetically induced multiferroic cupric oxide driven by intersublattice exchange

et al. 2014

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Magnetically induced ferroelectric multiferroics present an exciting new paradigm in the design of multifunctional materials, by intimately coupling magnetic and polar order. Magnetoelectricity creates a novel quasiparticle excitation-the electromagnon-at terahertz frequencies, with spectral signatures that unveil important spin interactions. To date, electromagnons have been discovered at low temperature (o70 K) and predominantly in rare-earth compounds such as RMnO 3 . Here we demonstrate using terahertz time-domain spectroscopy that intersublattice exchange in the improper multiferroic cupric oxide (CuO) creates electromagnons at substantially elevated temperatures (213-230 K). Dynamic magnetoelectric coupling can therefore be achieved in materials, such as CuO, that exhibit minimal static cross-coupling. The electromagnon strength and energy track the static polarization, highlighting the importance of the underlying cycloidal spin structure. Polarized neutron scattering and terahertz spectroscopy identify a magnon in the antiferromagnetic ground state, with a temperature dependence that suggests a significant role for biquadratic exchange.

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“…It was found that the application of critical magnetic field of 20 kOe suppressed the polarization P s states along the c-axis whereas it started increasing along the aaxis. [184,186] To confirm the origin and selection rules for these two peaks of TbMnO 3 and DyMnO 3 , light polarization-dependent measurements were performed. [184] Pimenov et al observed the new collective excitation corresponding to this multiferroic state known as electromagnon, i.e., electric-dipole active magnetic excitation in the imaginary part of the THz dielectric constant for GdMnO 3 and TbMnO 3 .…”

Section: Thz Studies On Multiferroic Rmnomentioning

confidence: 99%

Terahertz Electrodynamics in Transition Metal Oxides

Prajapati

Dagar

et al. 2019

Advanced Optical Materials

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201900958. 2−y 2 , d z 2 ) levels. [35] The splitting of the d-orbital was successfully explained by the crystal field theory. The ground state properties of these materials are mainly governed by the two interactions; i) the electron correlations (U) and, ii) SOC (λ) in the crystal field split narrow bands. [36] Among d electron systems, electrons in 3d TMOs experiences large electron correlations due to localized nature of 3d orbitals. The idea of electron-electron interaction was given by Sir N. F. Mott in 1949. It originated from the fact that the NiO was expected to be a metal according to the band theory, while the experiments showed insulating behavior. [37][38][39][40][41] This disagreement of experiments with the theory was explained by Hubbard who attributed the insulating state to the splitting

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Electrically active magnetic excitations in antiferromagnets (Review Article)

Cited by 18 publications

References 74 publications

Magnetization boundary conditions at a ferromagnetic interface of finite thickness

Magnetization boundary conditions at a ferromagnetic interface of finite thickness

High-temperature electromagnons in the magnetically induced multiferroic cupric oxide driven by intersublattice exchange

Terahertz Electrodynamics in Transition Metal Oxides

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