Raman- and infrared-active phonons in hexagonal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YMnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: Experiment and lattice-dynamical calculations

Iliev, M. N.; Lee, H.-G.; Popov, V. N.; Abrashev, M. V.; Hamed, A.; Meng, R. L.; Chu, C. W.

doi:10.1103/physrevb.56.2488

Cited by 205 publications

(145 citation statements)

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“…By the group theory analysis, the HexREMnO 3 has been reported to have 23 IR active phonon modes (9A1+ 14E1) [33]. In our work, the ambient REMnO 3 absorption spectrum shapes agree with the published results of YMnO 3 [33]. 11…”

Section: Resultssupporting

confidence: 82%

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High-pressure structural stability of multiferroic hexagonalRMnO3(R=Y, Ho, Lu)

et al. 2011

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Structural changes in REMnO 3 (RE= Y, Ho, Lu) under high pressure were examined by synchrotron x-ray diffraction methods at room temperature. Compression occurs more readily in the ab plane than along the c-axis. With increased pressure, a pressure-induced hexagonal to orthorhombic phase transition was observed starting at ~ 22 GPa for Lu(Y)MnO 3 . When the pressure is increased to 35 GPa, a small volume fraction of Lu(Y)MnO 3 is converted to the orthorhombic phase and the orthorhombic phase is maintained on pressure release. High pressure IR absorption spectroscopy and Mn K-edge near edge x-ray absorption spectroscopy confirm that the hexagonal P6 3 cm structure is stable below ~20 GPa and the environment around Mn ion is not changed. Shifts in the unoccupied p-band density of states with pressure are observed in the Mn K-Edge spectra. A schematic pressure-temperature phase diagram is given for the small ion REMnO 3 system.

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Section: Resultssupporting

confidence: 82%

“…Lorentzian oscillators [33] can index our ambient YMnO 3 OD spectrum well. The phonon assignments are listed in the Table 1 and compared to the measurements of Ref.…”

Section: Resultsmentioning

confidence: 99%

High-pressure structural stability of multiferroic hexagonalRMnO3(R=Y, Ho, Lu)

et al. 2011

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“…Optical studies on YMnO 3 also find clear evidence for coupling between the ferroelectric and antiferromagnetic domain walls [3], with measurements on the related compound HoMnO 3 demonstrating control of the magnetic phase using a static electric field [7]. The microscopic origin of the spin-charge coupling in YMnO 3 has also been investigated in detail using Raman scattering [8][9] and magnetoelastic measurements [6]. Raman studies on YMnO 3 thin films provide evidence for spin-phonon coupling below T N [9], while neutron measurements of spin excitations highlight the importance of magnetoelastic coupling in this system [6].…”

Section: Introductionmentioning

confidence: 99%

Suppression of multiferroic order in hexagonal ceramics

Dixit

Smith

Subramanian

et al. 2010

Solid State Communications

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We have investigated the effects of substituting In for Mn on the antiferromagnetic phase transition in YMnO 3 using magnetic, dielectric, and specific heat measurements. We prepared a set of isostructural phase pure hexagonal YMn 1-x In x O 3 samples having x=0 to x=0.9, which exhibit a systematic decrease of the antiferromagnetic ordering temperature with increasing In content. The multiferroic phase, which develops below T N , appears to be completely suppressed for x≥0.5 in the temperature range investigated, which can be attributed solely to the dilution of magnetic interactions as the crystal structure remains hexagonal. Similar to previous reports, we find an enhancement of the magnetocapacitive coupling on dilution with non-magnetic ions.

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“…The crystallographic, magnetic and electric properties of the hexagonal YMnO 3 and the other rare-earth manganites were studied in the sixties and the related data are available in [13]. New data concerning dielectric, magnetic, infrared and Raman studies have been also reported recently [14,15].…”

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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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Raman- and infrared-active phonons in hexagonalYMnO3: Experiment and lattice-dynamical calculations

Cited by 205 publications

References 11 publications

High-pressure structural stability of multiferroic hexagonalRMnO3(R=Y, Ho, Lu)

High-pressure structural stability of multiferroic hexagonalRMnO3(R=Y, Ho, Lu)

Suppression of multiferroic order in hexagonal ceramics

A generalized Ginzburg-Landau approach to second harmonic generation

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