Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds (4) [IIIII3] and (4) [IIIII3]

Carling, Simon G.; Visser, D.; Hautot, Dimitri; Watts, Ian D.; Day, Peter; Ensling, Jürgen; Gütlich, P.; Long, Gary J.; Grandjean, Fernande

doi:10.1142/9789812706836_0035

Cited by 5 publications

(8 citation statements)

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“…This reduced value is likely a result of the large unquenched orbital angular momentum in 1 , consistent with the strong magnetic anisotropy determined through magnetization experiments. Indeed, a similar phenomenon has been observed in the mixed-valence oxalates (PPh 4 )[Fe 2 (ox) 3 ] and (NBu 4 )[Fe 2 (ox) 3 ] …”

Section: Resultssupporting

confidence: 67%

Slow Magnetic Relaxation in a Family of Trigonal Pyramidal Iron(II) Pyrrolide Complexes

et al. 2010

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We present a family of trigonal pyramidal iron(II) complexes supported by tris(pyrrolyl-α-methyl)amine ligands of the general formula [M(solv)(n)][(tpa(R))Fe] (M = Na, R = tert-butyl (1), phenyl (4); M = K, R = mesityl (2), 2,4,6-triisopropylphenyl (3), 2,6-difluorophenyl (5)) and their characterization by X-ray crystallography, Mössbauer spectroscopy, and high-field EPR spectroscopy. Expanding on the discovery of slow magnetic relaxation in the recently reported mesityl derivative 2, this homologous series of high-spin iron(II) complexes enables an initial probe of how the ligand field influences the static and dynamic magnetic behavior. Magnetization experiments reveal large, uniaxial zero-field splitting parameters of D = -48, -44, -30, -26, and -6.2 cm(-1) for 1-5, respectively, demonstrating that the strength of axial magnetic anisotropy scales with increasing ligand field strength at the iron(II) center. In the case of 2,6-difluorophenyl substituted 5, high-field EPR experiments provide an independent determination of the zero-field splitting parameter (D = -4.397(9) cm(-1)) that is in reasonable agreement with that obtained from fits to magnetization data. Ac magnetic susceptibility measurements indicate field-dependent, thermally activated spin reversal barriers in complexes 1, 2, and 4 of U(eff) = 65, 42, and 25 cm(-1), respectively, with the barrier of 1 constituting the highest relaxation barrier yet observed for a mononuclear transition metal complex. In addition, in the case of 1, the large range of temperatures in which slow relaxation is observed has enabled us to fit the entire Arrhenius curve simultaneously to three distinct relaxation processes. Finally, zero-field Mössbauer spectra collected for 1 and 4 also reveal the presence of slow magnetic relaxation, with two independent relaxation barriers in 4 corresponding to the barrier obtained from ac susceptibility data and to the 3D energy gap between the M(S) = ±2 and ±1 levels, respectively.

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Section: Resultssupporting

confidence: 67%

Slow Magnetic Relaxation in a Family of Trigonal Pyramidal Iron(II) Pyrrolide Complexes

et al. 2010

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“…It is worth mentioning, on the other hand, that in the above quoted papers [9,10], at low temperatures, the Fe II sextet shows unusual very small B int values, close to 6 T, anyhow far from our data concerning the discussed compounds with bivalent iron listed in Table 3. Their interpretation inferred a positive value resulting from a negative Fermi-Contact term (spin only) contributions and a comparable but higher positive contribution related to an unquenched orbital moment [10], due to a trigonal symmetry around bivalent iron in those oxalate-containing compounds.…”

Section: Mössbauer Spectracontrasting

confidence: 59%

“…At room temperature (295 K), the experimental spectra lines are sharper, evidencing appropriate line widths for a coordination compound (G lower than 0.35 mm/s) ( Fig.10 and Table 3), and a lack of any noticeable relaxation process. The field at nucleus showed for Fe III values around 48 T and, respectively 44 T (see Table 3), smaller than those reported (close to 54 T) for compounds containing three oxalate groups [9,10], but larger than the one found in pure ferric oxalate. The patterns are labeled A and B to distinguish them, in Table 3, from the case of hetero-nuclear samples.…”

Section: Mössbauer Spectracontrasting

confidence: 52%

“…Their interpretation inferred a positive value resulting from a negative Fermi-Contact term (spin only) contributions and a comparable but higher positive contribution related to an unquenched orbital moment [10], due to a trigonal symmetry around bivalent iron in those oxalate-containing compounds. Their reasoning could be true (positive B int ), but was not confirmed via ''in field'' Mössbauer measurements.…”

Section: Mössbauer Spectramentioning

confidence: 99%

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Shaping distinct magnetic interactions in molecular compounds

Filoti

Bartolomé

Palade

et al. 2011

Journal of Magnetism and Magnetic Materials

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“…Interestingly, the magnetic hyperfine field of Fe3 II amounts to only ∼8.4 T, significantly lower than the typical ∼39 T for high-spin Fe II ions. This substantial reduction points toward the additional presence of an unquenched orbital moment, spin canting in the (Fe II ) 2 dimer and enhanced magnetic fluctuations.…”

Section: Resultsmentioning

confidence: 99%

A Mixed-Valent Iron (II/III) Diamond Chain with Single-Ion Anisotropy

et al. 2019

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The geometrically frustrated diamond spin chain system has yielded materials with a diversity of interesting magnetic properties but is predominantly limited to compounds with single-spin components. Here, we report the compound [(CH3)2NH2]6[FeIII 4FeII 2(μ3-O)2(μ3-OH)2(μ3-SO4)8] (1), which features the mixed-valent iron(II/III) diamond chain: ∞[FeIII–(FeIII)2–FeIII–(FeII)2]. 57Fe Mössbauer spectroscopy shows that two-thirds of the total spins in the ∞[FeIII 4FeII 2] diamond chain are spin-5/2 (high-spin FeIII), while the remaining one-third are spin-2 (high-spin FeII). To date, 1 is the only diamond-chain compound composed of more than one type of dimer, namely, (FeIII)2 and (FeII)2. On the basis of temperature-dependent 57Fe Mössbauer spectroscopy data, an alternating noncollinear 90° magnetic structure is proposed. Both the (FeIII)2 and (FeII)2 dimers are antiferromagnetically coupled and align in the direction along the chain axis ≈ [010], whereas the moments of the bridging FeIII monomers are oriented orthogonally. The spin canting, arising from the anisotropy of the FeII ions, leads to ferrimagnetic ordering at low temperatures.

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Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds (₄) [^II^III₃] and (₄) [^II^III₃]

Cited by 5 publications

References 0 publications

Slow Magnetic Relaxation in a Family of Trigonal Pyramidal Iron(II) Pyrrolide Complexes

Slow Magnetic Relaxation in a Family of Trigonal Pyramidal Iron(II) Pyrrolide Complexes

Shaping distinct magnetic interactions in molecular compounds

A Mixed-Valent Iron (II/III) Diamond Chain with Single-Ion Anisotropy

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