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Pashkevich, Yu. G.; Sobolev, V. L.; Fedorov, S. A.; Eremenko, A. V.

doi:10.1103/physrevb.51.15898

Cited by 6 publications

(9 citation statements)

References 19 publications

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“…1 Such kind of canting, which has nonrelativistic origin, supports the scattering on exchange magnons in the multisublattices exchange noncollinear magnets. 21 The one magnon contribution from exchange mechanisms appears under replacement one of the basis functions in the invariants shown in Table IV Table V we classify magnons at the magnetic  point by IRP of paramagnetic phase. This classification implies that small spin deviations can be described by magnetic basis functions (1).…”

Section: Cu1mentioning

confidence: 99%

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
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We performed Raman studies and a dielectric characterization of the pseudo-kagome Cu 3 Bi(SeO 3 ) 2 O 2 X (X = Cl, Br). These compounds share competing nearest-neighbour ferromagnetic exchange and frustrating next-nearest-neighbour antiferromagnetic exchange as well as highly noncollinear magnetic ground state. However, at low temperature they differ with respect to the existence of inversion symmetry. For both compounds there exists a pronounced interplay of polar phonon modes with quantum magnetic fluctuations. A novel Raman mode appears for temperatures below the Neel temperature with a Fano lineshape and an enormous intensity that exceeds most of the phonon lines. We discuss a possible contribution of longitudinal magnons to this signal. In contrast, one magnon scattering based on linear transvers magnons is excluded based on a symmetry analysis of spin wave representations and Raman tensor calculations. There exists evidence that in these pseudo-kagome compounds magnetic quantum fluctuations carry an electric dipole moment. Our data as well as a comparison with previous farinfrared spectra allow us to conclude that Cu 3 Bi(SeO 3 ) 2 O 2 Cl changes its symmetry most likely from Pmmn to P2 1 mn with a second order structural phase transition at T*=120 K and becomes multiferroic. Cu 3 Bi(SeO 3 ) 2 O 2 Br represents an interesting counter part as it does not show this instability and stays inversion symmetric down to lowest temperatures, investigated.PACS:

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Section: Cu1mentioning

confidence: 99%

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
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“…High scattering intensity can be provided by a few factors: i) strong DM interaction which is necessary for observation of exchange magnons in Raman experiments [18]; ii) contribution of exchange mechanism of Raman light scattering [19]; iii) existence of a few magnons with the same energy (quasidegeneration caused by the restricted number of exchange integrals for the description of 15 exchange magnons). Our preliminary measurements of Cu 2 OSeO 3 far-infrared (FIR) reflectance at 10 K [20] also demonstrate similar features in the same frequency region of spectra.…”

Section: Raman Spectra Of Cu 2 Oseomentioning

confidence: 99%

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

Gnezdilov

Lamonova

Pashkevich

et al. 2010

Low Temperature Physics

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We report Raman scattering studies and magneto/structural symmetry analysis of the many sublattices ferrimagnet Cu 2 OSeO 3 with a cubic symmetry and a linear magnetoelectric effect. There is no spectroscopic evidence for structural lattice distortions below T C = 60 K, 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 T C . 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 Cu 2 OSeO 3 .

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“…The irreducible representation which remains invariant under all symmetry elements of the magnetic group 6mm is B 1 , therefore ψ 3 is a good candidate to be defined as the antiferromagnetic order parameter [18] for YMnO 3 . ψ 3 is a complicated combination of the spin components of the six ions in the unit cell.…”

mentioning

confidence: 99%

“…The corresponding magnetic group is 6mm. Following Nedlin [17] and Pashkevich et al [18], we consider the following linear combinations of spins:…”

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A generalized Ginzburg-Landau approach to second harmonic generation

Valentí

Gros

2000

Eur. Phys. J. B

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We develop a generalized Ginzburg-Landau theory for second harmonic generation (SHG) in magnets by expanding the free energy in terms of the order parameter in the magnetic phase and the susceptibility tensor in the corresponding high-temperature phase. The non-zero components of the SHG susceptibility in the ordered phase are derived from the symmetries of the susceptibility tensor in the high-temperature phase and the symmetry of the order parameter. In this derivation, the dependence of the SHG susceptibility on the order parameter follows naturally, and therefore its nonreciprocal optical properties. We examine this phenomenology for the magnetoelectric compound Cr2O3 as well as for the ferroelectromagnet YMnO3. [3,4] in Cr 2 O 3 were obtained what confirms that these experiments can distinguish between the two magnetic states that are related to each other by the time reversal operation, and therefore its nonreciprocity. These observations can be explained by an interference effect between a time-symmetric magnetic dipole contribution and a time-antisymmetric electric dipole contribution [3]. Soon after these experiments were done, a microscopic theory was proposed [5] which could explain quantitatively the non-reciprocal effects observed in Cr 2 O 3 . It was shown that the electric dipole contributions were linearly proportional to the antiferromagnetic order parameter giving rise to the timeantisymmetric character to the electric dipole tensor. The study of this dependence is of crucial importance in order to understand the non-reciprocal character of the SHG tensors. The derivation of a micoscopic theory for a specific effect, in our case SHG, can be rather complicated depending on the properties of the material under study [5,6]. Concrete information of the SHG process in materials where a transition takes place, i.e. paramagnetantiferromagnet or paraelectric-ferroelectric, can be obtained at a simpler level, i.e. by considering only the symmetry arguments. In particular, we are interested in investigating the dependence of the SHG susceptibilities in the ordered phase on the order parameter.A powerful phenomenological theory suitable to describe phase transitions is the Ginzburg-Landau theory. The Ginzburg-Landau approach is based on the existence of an order parameter in the ordered phase and on symmetry considerations [7]. Pershan in 1963 [8] showed that the tensors for nonlinear electro-and magneto-optic effects could be derived from a phenomenological timeaveraged free energy. It is our purpose in this paper to extend the formulation of Pershan by including the order parameter explicitly in the expansion of the free energy for SHG. We shall show that the non-zero components of the SHG susceptibility tensor in the ordered phase are naturally obtained from the symmetry of the susceptibility tensor in the high-temperature phase and the symmetry of the order parameter. Once the dependence of the SHG susceptibility tensor on the order parameter is known, the non-reciprocal optical properties below the...

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Theory of Raman light scattering in the many-sublattice exchange-noncollinear magnetsUO2,RMnO3

Cited by 6 publications

References 19 publications

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
View full text Add to dashboard Cite

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
View full text Add to dashboard Cite

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

A generalized Ginzburg-Landau approach to second harmonic generation

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Theory of Raman light scattering in the many-sublattice exchange-noncollinear magnetsUO2,RMnO3

Cited by 6 publications

References 19 publications

Lattice and magnetic instabilities in Cu3Bi(SeO3)2OGnezdilov1, Pashkevich2, Lemmens3 et al. 2017Phys. Rev. B235190View full textAdd to dashboardCite

Lattice and magnetic instabilities in Cu3Bi(SeO3)2OGnezdilov1, Pashkevich2, Lemmens3 et al. 2017Phys. Rev. B235190View full textAdd to dashboardCite

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

A generalized Ginzburg-Landau approach to second harmonic generation

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Product

Resources

About

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
View full text Add to dashboard Cite

Lattice and magnetic instabilities in Cu3Bi(SeO3)2O
Gnezdilov
¹
,
Pashkevich
²
,
Lemmens
³

et al. 2017
Phys. Rev. B
23
5
19
0
View full text Add to dashboard Cite