Raman study of the NH+4 libration—phonon coupling in NH4MnF3

Rubín, Javier; Bartolomé, J.; Laguna, M. A.; Sanjuán, M. L.

doi:10.1016/0921-4526(95)00628-1

Cited by 7 publications

(5 citation statements)

References 13 publications

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“…This situation, again, has a strong resemblance with that found in ammonium and other small size alkylamonium halogenoperovskites and alkylamonium halogenoantimonates(III) and bismuthates(III) ,, that present a high temperature phase characterized by a considerable degree of freedom for rotational motion of alkylamonium cations inside the cavities defined by the [MX 6 ] n − octahedra. Meanwhile, diminution and freezing of their reorientational motion on lowering the temperature gives rise to low temperature polymorphs consisting in ordered phases of different nature (pyroelectric, ferroelectric, ferroelastic, etc.…”

Section: Discussionsupporting

confidence: 60%

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Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

et al. 2010

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We have found that the hybrid organic-inorganic perovskite-like formate Mn(HCOO)(3)[(CH(3))(2)NH(2)] shows a dielectric transition around 190 K. According to single crystal X-ray diffraction, the compound shows rhombohedral symmetry at room temperature and monoclinic symmetry at low temperature (100 K), and the main difference between both structures is that the (CH(3))(2)NH(2)(+) (DMA) cations are disordered in the high temperature phase but cooperatively ordered in the low temperature one. The vibrational spectra of this compound reveal that significant changes take place in the vibrations ascribed to the DMA cation (changes in the frequency of certain vibrations, splitting of particular vibrations, and changes in the intensities), while no significant changes have been observed in those attributed to the formate anion. On the basis of all this information, we attribute the origin of the dielectric transition to the dynamics of the DMA cations: above 190 K these cations can rotate inside the cubooctahedral cavity created by the [Mn(HCOO)(3)](-) framework, while for lower temperatures such rotation gets frozen, and their cooperative arrangement inside the cavities give rise to the observed dielectric transition.

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Section: Discussionsupporting

confidence: 60%

“…Meanwhile, diminution and freezing of their reorientational motion on lowering the temperature gives rise to low temperature polymorphs consisting in ordered phases of different nature (pyroelectric, ferroelectric, ferroelastic, etc. ). , …”

Section: Discussionmentioning

confidence: 99%

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

et al. 2010

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“…Besides, peaks within the same range are found at 2905 cm −1 , 2861 cm −1 , 1324 cm −1 and 1202 cm −1 , corresponding to the vibrations of PS chains whose presence is also confirmed by the TGA (Figure ), XRD (Figure ) and FTIR (Figure ) results. The liberational modes of MnF 6 are found at 354 cm −1 and 330 cm −1 in the Raman spectrum (Figure S2(b) supplementary data) of S2 measured in the range of 1000 cm −1 to 200 cm −1 . The Raman spectrum of sample S4 in the range of 800 cm −1 to 200 cm −1 is presented in Figure .…”

Section: Resultsmentioning

confidence: 93%

Fabrication and Characterization of Manganese‐based Self‐assembled Cubic Structures

et al. 2018

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Self‐assembled cubic structures of manganese‐based nanomaterials were achieved successfully, in case of manganese fluoride, for the very first time. The indirect synthesis of manganese oxide (Mn2O3) and manganese fluoride (MnF2/MnF3) self‐assembly involved an individual two step synthesis protocol. In first step of the protocol, NH4MnF3 self‐assembled cubic structures were fabricated by a simple liquid phase reaction using polystyrene (PS) as structure directing agent (SDA), while manganese nitrate tetrahydrate (Mn(NO3)2.4H2O) and ammonium fluoride (NH4F) as manganese and fluorine sources, respectively. In second step, the NH4MnF3 was transformed by calcination to manganese oxide (Mn2O3) at 450 °C for 5 hours under open atmosphere (air/O2), and individually, to manganese fluoride (MnF2/MnF3) at 350 °C for 5 hours under pure molecular fluorine (F2) environment. The temperature regimes for the transformation reactions were deduced from thermogravimetric analysis (TGA). The crystal structures and the compositions of all the samples were established by powder X‐rays diffraction (PXRD). Further, structural characterizations were carried out by spectroscopic analyses. The key objective, preservation of self‐assembled cubic structures in the resulting manganese oxide and fluoride, were confirmed by electron microscopic analyses. The self‐assembly structures formation mechanism was illustrated based on the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results.

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“…Our task was easy because vibrational spectra of tetraperoxometallate compounds with respect to the internal vibrations of the peroxo group in the dodecahedral [M(O 2 ) 4 ] 3– ion (where M = Cr 5+ ) had been reported before . In particular, it was of interest to study the temperature dependence of the low-frequency rotational, and librational modes of the NH 4 + ions which lie in this frequency range. , …”

Section: Resultsmentioning

confidence: 99%

Elucidating the Mechanism of Multiferroicity in (NH₄)₃Cr(O₂)₄ and Its Tailoring by Alkali Metal Substitution

et al. 2012

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The antiferromagnetic Cr(V) peroxychromates, M(3)Cr(O(2))(4), M = K, Rb, and Cs, become ferroelectric when mixed with NH(4)(+), but the underlying mechanism is not understood. Our dielectric relaxation, Raman scattering, and high-frequency EPR measurements on the M(3-x)(NH(4))(x)Cr(O(2))(4) family clarify this mechanism. At 295 K, (NH(4))(3)Cr(O(2))(4) is tetragonal (I42m), with the NH(4)(+) ions occupying two distinctly different sites, N1 and N2. A ferroelectric transition at T(c1) = 250 K is revealed by λ-type anomalies in C(p) and dielectric constant, and lowering of symmetry to Cmc2(1). Below T(c1), the N1 sites lose their tetrahedral symmetry and thus polarization develops. Raman detection of translational modes involving the NH(4)(+) ions around 193 cm(-1) supports this model. EPR around T(c1) revealed that the [Cr(O(2))(4)](3-) ions reorient by about 10°. A minor peak at T(c2) ≈ 207 K is attributed to a short-range ordering that culminates in a long-range, structural order at T(c3) ≈ 137 K. At T(c3), the symmetry is lowered to P1 with significant changes in the cell parameters. Rb(+) and Cs(+) substitutions that block the N1 and N2 sites selectively show that T(c1) is related to the torsional motion of the N1 site, while T(c2) and T(c3) are governed by the motional slowing down of the N2 site. These data show that the multiferroic behavior of this family is governed by the rotational and translational dynamics of the NH(4)(+) ions and is tunable by their controlled substitutions. Relevance to other classes of possible multiferroics is pointed out.

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Raman study of the NH+4 libration—phonon coupling in NH4MnF3

Cited by 7 publications

References 13 publications

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

Fabrication and Characterization of Manganese‐based Self‐assembled Cubic Structures

Elucidating the Mechanism of Multiferroicity in (NH₄)₃Cr(O₂)₄ and Its Tailoring by Alkali Metal Substitution

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Raman study of the NH+4 libration—phonon coupling in NH4MnF3

Cited by 7 publications

References 13 publications

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)3[(CH3)2NH2]

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)3[(CH3)2NH2]

Fabrication and Characterization of Manganese‐based Self‐assembled Cubic Structures

Elucidating the Mechanism of Multiferroicity in (NH4)3Cr(O2)4 and Its Tailoring by Alkali Metal Substitution

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Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

Characterization of the Order−Disorder Dielectric Transition in the Hybrid Organic−Inorganic Perovskite-Like Formate Mn(HCOO)₃[(CH₃)₂NH₂]

Elucidating the Mechanism of Multiferroicity in (NH₄)₃Cr(O₂)₄ and Its Tailoring by Alkali Metal Substitution