Thermal behavior in Pr(HCOO)<sub>3</sub> crystals

A combination of variable-temperature neutron scattering, reverse Monte Carlo analysis and direct Monte Carlo simulation is used to characterise the emergence of magnetic order in the metal-organic framework (MOF) Tb(HCOO)3 over the temperature range 100 K to 1.6 K = TN. We show that the magnetic transition at TN involves one-dimensional ferromagnetic ordering to a partially-ordered state related to the triangular Ising antiferromagnet. In this phase, the direction of magnetisation of ferromagnetic chains tends to alternate between neighbouring chains but this alternation is frustrated and is not itself ordered. In neutron scattering measurements this partial order gives rise to Bragg-like peaks, which cannot be interpreted using conventional magnetic crystallography without resort to unphysical spin models. The existence of low-dimensional magnetic order in Tb(HCOO)3 is stabilised by the contrasting strength of inter-and intra-chain magnetic coupling, itself a consequence of the underlying MOF architecture. Our results demonstrate how MOFs may provide an attractive if as yet under-explored platform for the realisation and investigation of low-dimensional physics.Low-dimensional magnets have long provided an important playground for the discovery and exploitation of unconventional physics [1]-from the earliest studies of soliton excitations in CsNiF 3 [2-4] to contemporary research into quantum information transport in spin-chain compounds [5]. The sensitivity of low-dimensional spin systems to small perturbations results in a rich diversity of phase transitions and complex ordering phenomena. By way of example, the Ising spin-chain compound Ca 3 Co 2 O 6 exhibits a variety of equilibrium and non-equilibrium states [6][7][8], characterised by e.g. long-wavelength incommensurate spin density modulations and field-induced magnetisation plateaux reminiscent of Hofstadter fractalisation [9,10]. In the field of low-dimensional magnetism, arguably the strongest scientific interest from both experimental and theoretical perspectives has always been in the limit of strict 1D order [11][12][13][14][15][16]. Yet even in canonical systems such as Ca 3 Co 2 O 6 the divergence of correlation lengths along 1D spin chains is always accompanied by full 3D magnetic order [8,17]. So the realisation and experimental characterisation of genuine partially-ordered low-dimensional spin states remain an important challenge in the field.It was in this context that we chose to study magnetic order in terbium(III) formate, Tb(HCOO) 3 . In metal-organic frameworks (MOFs) such as Tb(HCOO) 3 , magneticallyactive transition-metal or rare-earth ions are connected via organic ligands to form extended 3D framework structures. Because organic ligands can support superexchange interactions that span a broad energy range, and because framework design allows controlled incorporation of low-dimensional structural motifs (e.g. chains, ladders, layers), MOFs are natural candidate hosts for low-dimensional magnetism [18]. Indeed the magnetic response of...

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“…1(b)]. There is no experimental evidence for any change in space group symmetry between room temperature and 1.4 K [25,33,34].…”

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confidence: 99%

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

et al. 2016

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“…The corresponding Raman bands are very weak. These bands are shifted by about 100 cm 1 towards higher wavenumbers in comparison with anhydrous Pr(HCOO) 3 and are observed 11,12 at similar wavenumbers as the corresponding bands in Ca 2 Cu(HCOO) 6 . It is worth noting that the Raman spectra show also the presence of a broad and weak band near 1555 cm 1 .…”

Section: Polarized Ir and Spontaneous Raman Spectramentioning

confidence: 82%

Polarized IR, spontaneous and stimulated Raman spectra of Y(HCOO)3·2H2O single crystal — a new Raman laser material

Mączka

Hanuza

Kaminskii

2006

J. Raman Spectrosc.

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Polarized Raman and IR spectra have been measured for Y(HCOO) 3 ·2H 2 O single crystal at room temperature. Assignment of the observed bands to the respective internal and external vibrations was proposed on the basis of factor group approach for the orthorhombic P2 1 2 1 2 1 (D 4 2 ) space group and the literature data for the other metal formates. The results obtained for the spontaneous Raman scattering have been used in the discussion of the stimulated Raman spectra of the material studied.

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“…In this structure, the RE and HCOO species are at 3a(C 3v ) and 9b(C s xz ) symmetry sites, respectively. From the 39 normal modes of this compound, just 32 are optical-active (Raman and IR) modes and can be decomposed at the center of the Brillouin zone according to the irreducible representations of the C 3v point group in the following way [14] = 8A 1 (2T, L, ν 1 , . .…”

Section: Resultsmentioning

confidence: 99%

“…[14] Polarized Raman spectra were recorded on a Jobin-Yvon T64000 triplemate spectrometer using the lines of an argon ion laser (Coherent Innova 70) operating at 50 mW. The slit widths were adjusted to yield a 2 cm −1 of spectral resolution and the spectra were recorded with a liquid N 2 -cooled CCD detector.…”

Section: Methodsmentioning

confidence: 99%

“…In 1981, Kartha and Venkateswaran [13] presented the Raman spectra of RE(HCOO) 3 and RE(DCOO) 3 compounds. In 2004, Moura et al [14] presented a thermal analysis and a temperature-dependent Raman spectroscopic study of Pr(HCOO) 3 in the range 300-10 K, where the room-temperature Raman phonons were assigned based on the correlations with the results published in Refs. [12 and 13].…”

Section: Introductionmentioning

confidence: 99%

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Vibrational modes of rare‐earth formates

Silva

Moura

Ayala

et al. 2009

J Raman Spectroscopy

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In this work we investigate the room-temperature Raman spectra of several rare-earth [RE(HCOO) 3 ; RE = La, Pr, Nd, Gd, Tb and Y] formates. Polarized measurements were carried out for La(HCOO) 3 yielding the observation of most of the Ramanactive phonons predicted by group theory analysis. The respective assignment is given based on the formate vibrations and correlations with previous results in other RE(HCOO) 3 systems. The wavenumber 'softening' observed when RE goes from Y to La is accounted for the lattice expansion.

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Thermal behavior in Pr(HCOO)₃ crystals

Cited by 6 publications

References 18 publications

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

Polarized IR, spontaneous and stimulated Raman spectra of Y(HCOO)3·2H2O single crystal — a new Raman laser material

Vibrational modes of rare‐earth formates

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Thermal behavior in Pr(HCOO)3 crystals

Cited by 6 publications

References 18 publications

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

Polarized IR, spontaneous and stimulated Raman spectra of Y(HCOO)3·2H2O single crystal — a new Raman laser material

Vibrational modes of rare‐earth formates

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Thermal behavior in Pr(HCOO)₃ crystals