Raman and infrared-active phonons in hexagonal HoMnO<sub>3</sub>single crystals: magnetic ordering effects

Litvinchuk, A. P.; Iliev, M. N.; Popov, V. N.; Gospodinov, M.

doi:10.1088/0953-8984/16/6/011

Cited by 96 publications

(117 citation statements)

References 24 publications

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“…Further signatures for the strong coupling of the magnetic order to the lattice or phonons was derived from Raman experiments showing an enhancement of the phonon frequencies of two modes, which modulate the Mn-Mn interaction, below the Néel temperature of HoMnO 3 [128]. A similar phonon enhancement had also been reported for hexagonal LuMnO 3 near [129].…”

Section: Magnetic Order and Dielectric And Thermodynamicsupporting

confidence: 57%

“…An elastic softening was observed over a wide temperature range, with pronounced anomalies at SR and Ho , and it was attributed to spin fluctuations induced by the Ho-Mn interactions. It should also be noted that magnetic ordering effects below result in a sizable hardening of phonon modes that modulate the Mn-Mn interactions which is further evidence of the strong spin-lattice coupling in HoMnO 3 [128].…”

Section: Magnetoelastic Effects As Evidence For Strong Spin-lattice Cmentioning

confidence: 90%

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Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Lorenz

2013

ISRN Condensed Matter Physics

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Hexagonal manganites belong to an exciting class of materials exhibiting strong interactions between a highly frustrated magnetic system, the ferroelectric polarization, and the lattice. The existence and mutual interaction of different magnetic ions (Mn and rare earth) results in complex magnetic phase diagrams and novel physical phenomena. A summary and discussion of the various properties, underlying physical mechanisms, the role of the rare earth ions, and the complex interactions in multiferroic hexagonal manganites, are presented in this paper.

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Section: Magnetic Order and Dielectric And Thermodynamicsupporting

confidence: 57%

Section: Magnetoelastic Effects As Evidence For Strong Spin-lattice Cmentioning

confidence: 90%

Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Lorenz

2013

ISRN Condensed Matter Physics

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“…5 (c,d)). This could be due to the variation of relevant bond distances, documented in the neutron diffraction studies [5,7] and/or the effect of magnetic order on corresponding force constants, similar to those reported for other magnetic materials [21,22].It is important to note that the dielectric response of La 1/2 Ca 1/2 MnO 3 , as obtained from the reflection spectroscopy data, is consistent with the phase separation sce-3 nario for manganese oxides (see review [23] and references cites therein). Indeed, even below T N the dielectric function is not typical of an insulator, but contains the Drudelike component, a signature for presence in the sample of a conducting phase.…”

supporting

confidence: 69%

Charge and lattice dynamics of ordered state in La1/2Ca1/2MnO3: infrared reflection spectroscopy study

Litvinchuk¹,

Iliev²,

Pissas³

et al. 2004

Solid State Communications

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We report an infrared reflection spectroscopy study of La 1/2 Ca 1/2 MnO3 over a broad frequency range and temperature interval which covers the transitions from the high temperature paramagnetic to ferromagnetic and, upon further cooling, to antiferromagnetic phase. The structural phase transition, accompanied by a ferromagnetic ordering at TC =234 K, leads to enrichment of the phonon spectrum. A charge ordered antiferromagnetic insulating ground state develops below the Néel transition temperature TN =163 K. This is evidenced by the formation of charge density waves and opening of a gap with the magnitude of 2∆0 = (320 ± 15) cm −1 in the excitation spectrum. Several of the infrared active phonons are found to exhibit anomalous frequency softening. The experimental data suggest coexistence of ferromagnetic and antiferromangetic phases at low temperatures. PACS numbers:Manganite perovskites R 1−x A x MnO 3 (where R is a trivalent rare earth and A is a divalent alkaline rare earth) exhibit rich phase diagram and a variety of intriguing properties due the delicate interplay of spin, charge, lattice, and orbital degrees of freedom (Ref. [1,2,3] and references cited therein). Well defined anomalies of physical properties at commensurate carrier concentrations of x=N/8 (where N=1, 3, 4, 5, and 7) and x = L/3 (where L=1,2) were unambiguously established. Of particular interest is the phenomenon of charge and orbital ordering, most clearly pronounced for x=1/2 [4,5,6,7,8,9,10].In this communication we report the results of an infrared reflection study of La 1/2 Ca 1/2 MnO 3 over broad frequency range and at temperatures, covering the transitions from the high temperature paramagnetic to ferromagnetic and, upon further cooling, to antiferromagnetic phase. By making use of Kramers-Kronig analysis we obtained the spectral dependence of conductivity. Its analysis yields information on the evolution of phonons and electronic excitations as a function of temperature. We found that additional phonon modes appear in the spectra in the ferromagnetic phase, a fact which implies the occurrence of a structural phase transition. Upon further cooling the conductivity spectrum shows development of a gap, which signals the formation of a charge ordered state at low temperatures. At the same time a Drude-like component of the conductivity does not vanish completely and suggests the coexistence of a metallic and insulating phases.The measurements were performed on a dense ceramic pellet of La 1/2 Ca 1/2 MnO 3 , mechanically polished to optical quality. The material preparation technique is described in Ref. [3,9,11]. The samples were intensively characterized by the X-ray scattering, neutron diffraction, magnetization measurements, Raman scattering as well as Mössbauer spectroscopy (doped with 1% Sn or Fe). These measurements unambiguously identified the transition from the paramagnetic to ferromagnetic phase at T C =234 K, and further to antiferromagnetic phase at T c N =163 K (cooling cycle) or T h N =196 K (heating cycle), see The re...

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“…The point where two such adjacent curves join can be regarded as the phase transition temperature. [38][39][40] The data in Fig. 8 are modeled with two curves of Eq.…”

Section: Raman Spectroscopy Of Unmodified and Fe-modified Nbtmentioning

confidence: 99%

Structure and properties of Fe-modified Na0.5Bi0.5TiO3at ambient

et al. 2012

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Sodium bismuth titanate (NBT) ceramics are among the most promising lead-free materials for piezoelectric applications. This work reports the crystal structure and phase evolution of NBT and Fe-modified NBT (from 0-2 at% Fe) using synchrotron X-ray diffraction and Raman spectroscopy, both at ambient and elevated temperatures. The crystallographic results are discussed with reference to permittivity and piezoelectric thermal depolarization measurements of the same compositions. Changes in the depolarization temperature due to Fe substitution were detected by Raman spectroscopy, and were found to correlate closely with depolarization temperatures obtained from converse piezoelectric coefficient and permittivity measured in situ. The depolarization temperatures obtained from direct piezoelectric coefficient measured ex situ as well as the phase transition temperatures obtained from synchrotron X-ray diffraction were found to be at higher temperatures. The mechanisms underlying the relationship between permittivity and piezoelectric depolarization to structural transitions observed in Raman spectroscopy and X-ray diffraction are discussed.

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Raman and infrared-active phonons in hexagonal HoMnO₃single crystals: magnetic ordering effects

Cited by 96 publications

References 24 publications

Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Charge and lattice dynamics of ordered state in La1/2Ca1/2MnO3: infrared reflection spectroscopy study

Structure and properties of Fe-modified Na0.5Bi0.5TiO3at ambient

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Raman and infrared-active phonons in hexagonal HoMnO3single crystals: magnetic ordering effects

Cited by 96 publications

References 24 publications

Hexagonal Manganites—(RMnO3): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Hexagonal Manganites—(RMnO3): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Charge and lattice dynamics of ordered state in La1/2Ca1/2MnO3: infrared reflection spectroscopy study

Structure and properties of Fe-modified Na0.5Bi0.5TiO3at ambient

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Product

Resources

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Raman and infrared-active phonons in hexagonal HoMnO₃single crystals: magnetic ordering effects

Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity

Hexagonal Manganites—(RMnO₃): Class (I) Multiferroics with Strong Coupling of Magnetism and Ferroelectricity