Chapter 199 Neutron scattering studies of lanthanide magnetic ordering

Lynn, J. W.; Skanthakumar, S.

doi:10.1016/s0168-1273(01)31008-5

Cited by 8 publications

(5 citation statements)

References 128 publications

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“…Although the moment correlations are expected to become negligible at temperatures above about twice the magnetic ordering temperature, the nonlinear M versus H curves shown in Figure are evidence that they persist to temperatures as high as 20 K in (NpO 2 ) 2 (SeO 4 )(H 2 O) 4 . Persistence of correlations well above the transition temperature has been previously reported in layered materials in which in-plane coupling is stronger than any out-of-plane interactions, the latter of which may include competitive coupling forces. , The difference in Np–Np in plane distances, about 4.1–4.2 Å, from the out-of-plane shortest Np–Np interactions of 7.2–7.4 Å supports this interpretation.…”

Section: Resultssupporting

confidence: 64%

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

2011

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Green crystals of (NpO(2))(2)(SeO(4))(H(2)O)(4), (NpO(2))(2)(SeO(4))(H(2)O)(2), and (NpO(2))(2)(SeO(4))(H(2)O) have been prepared by hydrothermal methods. The structures of these compounds have been characterized by single-crystal X-ray diffraction. (NpO(2))(2)(SeO(4))(H(2)O)(4), isostructural with (NpO(2))(2)(SO(4))(H(2)O)(4), is constructed from layers comprised of corner-sharing neptunyl(V) pentagonal bipyramids and selenate tetrahedra that are further linked by hydrogen bonding with water molecules. Each NpO(2)(+) cation binds to four other NpO(2)(+) units through cation-cation interactions (CCIs) to form a distorted "cationic square net" decorated by SeO(4)(2-) tetrahedra above and below the layer. Each selenate anion is bound to two neptunyl(V) cations through monodentate linkages. (NpO(2))(2)(SeO(4))(H(2)O)(2) is isostructural with the corresponding sulfate analogue as well. It consists of puckered layers of neptunyl(V) pentagonal bipyramids that are further connected by selenate tetrahedra to form a three-dimensional framework. The CCI pattern in the neptunyl layers of dihydrate is very similar to that of tetrahydrate; however, each SeO(4)(2-) tetrahedron is bound to four NpO(2)(+) cations in a mondentate manner. (NpO(2))(2)(SeO(4))(H(2)O) crystallizes in the monoclinic space group P2(1)/c, which differs from the (NpO(2))(2)(SO(4))(H(2)O) orthorhombic structure due to the slightly different connectivities between NpO(2)(+) cations and anionic ligands. The structure of (NpO(2))(2)(SeO(4))(H(2)O) adopts a three-dimensional network of distort neptunyl(V) pentagonal bipyramids decorated by selenate tetrahedra. Each NpO(2)(+) cation connects to four other NpO(2)(+) units through CCIs and also shares an equatorial coordinating oxygen atom with one of the other units in addition to the CC bond to form a dimer. Each SeO(4)(2-) tetrahedron is bound to five NpO(2)(+) cations in a monodentate manner. Magnetic measurements obtained from the powdered tetrahydrate are consistent with a ferromagnetic ordering of the neptunyl(V) spins at 8(1) K, with an average low temperature saturation moment of 1.98(8) μ(B) per Np. Well above the ordering temperature, the susceptibility follows Curie-Weiss behavior, with an average effective moment of 3.4(2) μ(B) per Np and a Weiss constant of 14(4) K. Correlations between lattice dimensionality and magnetic behavior are discussed.

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Section: Resultssupporting

confidence: 64%

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

2011

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“…The appearance and behavior of T k with increasing field is suggestive of a transition to an antiferromagnetic state for the Gd 3+ ion subsystem at low temperature. This type of transition is ubiquitous in high-T c cuprates with rare-earth components [23]. For example, it is found in Gd cuprates that antiferromagnetic ordering of Gd 3+ ions takes place at a T N of 2.3-2.4 K for double CuO 2 layer compounds; whereas, for single-layer ones a higher T N (up to 6.6 K) is revealed [7,24].…”

Section: Crossing Point Effectmentioning

confidence: 94%

Characteristic crossing point (T_*≈2.7 K) in specific heat curves of samples RuSr₂Gd_1.5Ce_0.5Cu₂O_10−δtaken for different values of magnetic field

Белевцев

Krasovitsky

Naugle

et al. 2009

J. Phys.: Condens. Matter

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Magnetic properties of polycrystalline samples of RuSr(2)(Gd(1.5)Ce(0.5))Cu(2)O(10-δ), as-prepared (by solid-state reaction) and annealed (12 h at 845 °C) in pure oxygen at different pressure (30, 62 and 78 atm) are presented. The specific heat and magnetization were investigated in the temperature range 1.8-300 K with a magnetic field up to 8 T. The specific heat, C(T), shows a jump at the superconducting transition (with an onset at T≈37.5 K). Below 20 K, a Schottky-type anomaly becomes apparent in C(T). This low-temperature anomaly can be attributed to splitting of the ground term (8)S(7/2) of paramagnetic Gd(3+) ions by internal and external magnetic fields. It is found that curves C(T) taken for different values of magnetic field have the same crossing point (at T(*)≈2.7 K) for all the samples studied. At the same time, C(H) curves taken for different temperatures have a crossing point at a characteristic field H(*)≈3.7 T. These effects can be considered as a manifestation of the crossing point phenomenon which is supposed to be inherent for strongly correlated electron systems.

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“…Technical difficulties in obtaining the susceptibility data that arise in part from safety concerns associated with handling a radionuclide, notably the use of only small sample sizes and the requirement for encapsulation, which contributes to the background, render it not possible to determine within error limits whether the U sublattice is diamagnetic (U 6+ ) or exhibits a positive signal consistent with a TIP. The presence of Cu in these materials further complicates the issue because it can contribute to a TIP response. , A large TIP could indicate the stoichiometric presence of U 4+ . A solely TIP response has been previously observed at higher temperatures (60–300 K) for BaUO 3 , a tetravalent U ion octahedrally coordinated with six oxygen atoms in full cubic symmetry .…”

Section: Resultsmentioning

confidence: 99%

“…The presence of Cu in these materials further complicates the issue because it can contribute to a TIP response. 71,72 A large TIP could indicate the stoichiometric presence of U 4+ . A solely TIP response has been previously observed at higher temperatures (60−300 K) for BaUO 3 , a tetravalent U ion octahedrally coordinated with six oxygen atoms in full cubic symmetry.…”

Section: ■ Introductionmentioning

confidence: 99%

Oxidation State of Uranium in A₆Cu₁₂U₂S₁₅(A = K, Rb, Cs) Compounds

Malliakas

Yao²,

Wells³

et al. 2012

Inorg. Chem.

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Black single crystals of A(6)Cu(12)U(2)S(15) (A = K, Rb, Cs) have been synthesized by the reactive flux method. These isostructural compounds crystallize in the cubic space group Ia ̅3d at room temperature. The structure comprises a three-dimensional framework built from US(6) octahedra and CuS(3) trigonal planar units with A cations residing in the cavities. There are no S-S bonds in the structure. To elucidate the oxidation state of U in these compounds, various physical property measurements and characterization methods were carried out. Temperature-dependent electrical resistivity measurement on a single crystal of K(6)Cu(12)U(2)S(15) showed it to be a semiconductor. These three A(6)Cu(12)U(2)S(15) (A = K, Rb, Cs) compounds all exhibit small effective magnetic moments, < 0.58 μ(B)/U and band gaps of about 0.55(2) eV in their optical absorption spectra. From X-ray absorption near edge spectroscopy (XANES), the absorption edge of A(6)Cu(12)U(2)S(15) is very close to that of UO(3). Electronic band structure calculations at the density functional theory (DFT) level indicate a strong degree of covalency between U and S atoms, but theory was not conclusive about the formal oxidation state of U. All experimental data suggest that the A(6)Cu(12)U(2)S(15) family is best described as an intermediate U(5+)/U(6+) sulfide system of (A(+))(6)(Cu(+))(12)(U(5+))(2)(S(2-))(13)(S(-))(2) and (A(+))(6)(Cu(+))(12)(U(6+))(2)(S(2-))(15).

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Chapter 199 Neutron scattering studies of lanthanide magnetic ordering

Cited by 8 publications

References 128 publications

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

Characteristic crossing point (T_*≈2.7 K) in specific heat curves of samples RuSr₂Gd_1.5Ce_0.5Cu₂O_10−δtaken for different values of magnetic field

Oxidation State of Uranium in A₆Cu₁₂U₂S₁₅(A = K, Rb, Cs) Compounds

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Chapter 199 Neutron scattering studies of lanthanide magnetic ordering

Cited by 8 publications

References 128 publications

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO2)2(SeO4)(H2O)n (n = 1, 2, and 4)

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO2)2(SeO4)(H2O)n (n = 1, 2, and 4)

Characteristic crossing point (T*≈2.7 K) in specific heat curves of samples RuSr2Gd1.5Ce0.5Cu2O10−δtaken for different values of magnetic field

Oxidation State of Uranium in A6Cu12U2S15(A = K, Rb, Cs) Compounds

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Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

Cation–Cation Interactions: Crystal Structures of Neptunyl(V) Selenate Hydrates, (NpO₂)₂(SeO₄)(H₂O)_n (n = 1, 2, and 4)

Characteristic crossing point (T_*≈2.7 K) in specific heat curves of samples RuSr₂Gd_1.5Ce_0.5Cu₂O_10−δtaken for different values of magnetic field

Oxidation State of Uranium in A₆Cu₁₂U₂S₁₅(A = K, Rb, Cs) Compounds