Towards unravelling the Rosette agent enigma: Spread and emergence of the co-invasive host-pathogen complex, Pseudorasbora parva-Sphaerothecum destruens.

The emergence of non-native fungal pathogens is a growing threat to global health, biodiversity, conservation biology, food security and the global economy. Moreover, a thorough understanding of the spread and emergence of pathogens among invasive and native host populations, as well as genetic analysis of the structure of co-invasive host populations, is crucial in terms of conservation biology and management strategies. Here we combined extensive catchment sampling, molecular detection tools and genomic signatures to i) assess the prevalence of the rosette agent Sphaerothecum destruens in invasive and native fish populations in contrasting french regions, and ii) characterize the genetic diversity and population structure of its co-invasive and asymptomatic carrier Pseudorasbora parva. Although S. destruens was not detected in all the fish collected its presence in contrasting freshwater ecosystems suggests that the disease may already be widespread in France. Furthermore, our results show that the detection of S. destruens DNA in its asymptomatic carrier P. parva is still limited. Finally, we found that P. parva populations show a homogeneous genetic and geographical structuring, which raises the possibility of the occurrence of successive introduction events in France from their native and invasive range.

New type of magnetic structure in the R2T2X group: Tb2Pd2In.

Anisotropy of bulk magnetic properties and magnetic structure studies of a Tb2Pd2In single crystal by means of bulk magnetization methods and neutron diffraction techniques confirmed the antiferromagnetic order below the Néel temperature 29.5 K. The collinear magnetic structure of Tb magnetic moments aligned along the tetragonal c-axis is characterized by a propagation vector k = (1/4, 1/4, 1/2), yielding an equal-moment structure with alternating coupling between nearest as well as next-nearest Tb neighbors within the basal plane and antiferromagnetic coupling between the c-axis neighbors. In the context of magnetism of R2T2X compounds, where R stands for rare-earth or actinide element, such collinear structure with long-wavelength periodicity represents a new type of magnetic structure.

(Nd/Pr)2NiO4+δ: Reaction Intermediates and Redox Behavior Explored by in Situ Neutron Powder Diffraction during Electrochemical Oxygen Intercalation.

Oxygen intercalation/deintercalation in Pr2NiO4+δ and Nd2NiO4+δ was followed by in situ neutron powder diffraction during electrochemical oxidation/reduction, in a dedicated reaction cell at room temperature. For both systems three phases, all showing the same line width, were identified. The starting phases Pr2NiO4.23 and Nd2NiO4.24, considered with an average orthorhombic Fmmm symmetry, although both show a slight monoclinic distortion, get reduced in a two-phase reaction step to tetragonal intermediate phases with 0.07 ≤ δ ≤ 0.10 and P42/ ncm space group, which on further reduction transform, again in a two-phase reaction step, toward the respective stoichiometric (Pr/Nd)2NiO4.0 phases, with Bmab space group. Electrochemical oxidation does, however, not proceed fully reversibly for both cases: while the reoxidation of Nd2NiO4+δ is limited to the tetragonal intermediate phase with δ = 0.10, the homologous Pr2NiO4+δ can be reoxidized up to δ = 0.17, showing orthorhombic symmetry. For the intermediate tetragonal phase, we were able to establish for Pr2NiO4.09 a complex anharmonic displacement behavior of the apical oxygen atoms, as analyzed by single-crystal neutron diffraction and maximum entropy analysis, in agreement with a low- T diffusion pathway for oxygen ions, activated by lattice dynamics.

Phase transitions and magnetic structures in MnW1-x Mo x O4 compounds (x ⩽ 0.2).

Temperature-dependent specific heat, magnetization and neutron diffraction data have been collected in zero magnetic field for polycrystalline samples of MnW1-x Mo x O4 (x ⩽ 0.2) solid solution whose end-member MnWO4 exhibits a magnetoelectric multiferroic phase (AF2 phase) between T 1 ≈ 8 K and T 2 = 12.5 K. In MnW1-x Mo x O4, diamagnetic W(6+) are replaced with diamagnetic Mo(6+) cations and magnetic couplings among Mn(2+) (3d (5), S = 5/2) ions are modified due the doping-induced tuning of the orbital hybridization between Mn 3d and O 2p states. It was observed that magnetic phase transition temperatures which are associated with the second-order AF3-to-paramagnetic (T N) and AF2-to-AF3 (T 2) transitions in pure MnWO4 slightly increase with the Mo content x. Magnetic specific heat data also indicate that the first-order AF1-to-AF2 phase transition at T 1 survives a weak doping x ⩽ 0.05. This latter phase transition becomes invisible above the base temperature 2 K for higher level of doping x ⩾ 0.10. Neutron powder diffraction datasets collected above 1.5 K for a sample of MnW0.8Mo0.2O4 were analyzed using the Rietveld method. The magnetic structure below ≈ 14 K is a helical incommensurate spin order with a temperature-independent propagation vector k = (-0.217(6), 0.5, 0.466(4)). This cycloidal magnetic structure is similar to the polar AF2 structure observed in MnWO4. The AF1 up-up-down-down collinear spin arrangement observed in MnWO4 is absent in our MnW0.8Mo0.2O4 sample.

Crystal structure of monoclinic calcium pyrophosphate dihydrate (m-CPPD) involved in inflammatory reactions and osteoarthritis.

Pure monoclinic calcium pyrophosphate dihydrate (m-CPPD) has been synthesized and characterized by synchrotron powder X-ray diffraction and neutron diffraction. Rietveld refinement of complementary diffraction data has, for the first time, allowed the crystal structure of m-CPPD to be solved. The monoclinic system P2(1)/n was confirmed and unit-cell parameters determined: a = 12.60842 (4), b = 9.24278 (4), c = 6.74885 (2) Å and ß = 104.9916 (3)°. Neutron diffraction data especially have allowed the precise determination of the position of H atoms in the structure. The relationship between the m-CPPD crystal structure and that of the triclinic calcium pyrophosphate dihydrate (t-CPPD) phase as well as other pyrophosphate phases involving other divalent cations are discussed by considering the inflammatory potential of these phases and/or their involvement in different diseases. These original structural data represent a key step in the understanding of the mechanisms of crystal formation involved in different types of arthritis and to improve early detection of calcium pyrophosphate (CPP) phases in vivo.

Study of the magnetic and electronic properties of nanocrystalline PrCo3 by neutron powder diffraction and density functional theory.

Nanocrystalline PrCo(3) powder has been synthesized by high-energy milling and was subsequently annealed from 873 to 1273 K for 30 min to optimize the extrinsic properties. The structure and magnetic properties of the nanocrystalline PrCo(3) have been investigated by means of x-ray and neutron diffraction as well as magnetization measurements. All compounds crystallize in the same PuNi(3) type structure, with grain sizes between 28 and 47 nm. As the annealing temperature increases, a maximum coercive field of 12 kOe at 300 K (55 kOe at 10 K) was obtained by annealing at 1023 K for a grain size of 35 nm. The refinement of the neutron powder diffraction patterns (NPD) of PrCo(3) from 1.8 to 300 K shows an expansion of the parameter a and a contraction of the parameter c, leading to a decrease of the ratio c/a. The evolution of the Co and Pr magnetic sublattices measured by NPD indicates that this compound is a highly anisotropic uniaxial ferromagnet with the easy magnetization axis parallel to c(-->). This experimental study has been completed by a theoretical investigation of the electronic structure of the PrCo(x) (x = 2, 3 and 5) compounds. Band structure calculations with collinear spin polarization were performed by using the local approximation of the density functional theory scheme implemented in the projector-augmented wave method. The electronic structure of PrCo(3) compound in both directions of spin shows that the majority of occupied states are dominated by the 3d states of Co, with a strong electronic charge transfer from Pr to Co. The PrCo(3) electronic structure can be explained by a superimposition of those of PrCo(2) and PrCo(5), as expected from its crystal structure. The magnetic anisotropy has been confirmed for PrCo(3), as a non-collinear spin calculation with the polarization along the c axis is shown to be more stable than with the polarization in the (a(-->),b(-->)) plane.

Mixed metallic Ba(Co,Fe)X(0.2)O(3-δ) (X = F, Cl) hexagonal perovskites: drastic effect of Fe-incorporation on structural and electronic features.

Starting from the parent 10H-Ba(5)Co(5)X(1-x)O(13-δ) (trimeric strings of face-sharing CoO(6) octahedra with terminal CoO(4) tetrahedra, stacking sequence (chhch')(2)) and 6H-Ba(6)Co(6)X(1-x)O(16-δ) (similar with tetrameric strings, stacking sequence chhhch') hexagonal perovskites forms (X = F, Cl; c, h = [BaO(3)] layers ; h' = [BaOX(1-y)] layers), we show here that the Fe incorporation leads to large domains of solid solutions for both X = F and Cl but exclusively stabilizes the 10H-form independently of the synthesis method. In this form, the lowest concentration of h-layers is stabilized by a sensitive metal reduction with increasing the Fe ratio. In a more general context of competition between several hexagonal perovskite polymorphs available for most of the transition metals, this redox change is most probably the key factor driving 1D (face-sharing chains) to 3D (corner-sharing) connectivities. Strikingly, ND data evidence the location of oxygen deficiencies in the tetrahedral (Co/Fe) coordination. This effect is exaggerated at high temperature, while (Co/Fe)O(4-δ) coordinations are completed by the displacement of X(-) anions toward the (Co/Fe) sphere of coordination following a "push-and-pull" mechanism within h'-[BaOX(1-y)] layers. The Fe-incorporation is also accompanied by increasing conduction gaps with predominant 1D variable range hopping. The full series show antiferromagnetic behavior with increasing T(N) as [Fe] increases. For Fe-rich compounds T(N) is estimated about 600 K, as rarely observed for hexagonal perovskite compounds. Finally, magnetic structures of all iron-doped compounds show a site-to-site AFM ordering, different of the magnetic structure of Co-only parent compounds. Here, DFT calculations predict low-spin octahedral Co configurations, but high-spin Fe species in the same sites.

Crystal and magnetic structures and magnetic properties of selenate containing natrochalcite, A(I)M(II)2(H3O2)(SeO4)2 where A = Na or K and M = Mn, Co, or Ni.

The synthesis of a series of selenate containing natrochalcite, A(I)M(II)(2)(H(3)O(2))(SeO(4))(2) where A = Na or K and M = Mn, Co, or Ni (here labeled as AMH and AMD for the hydrogenated and deuterated compounds, respectively), the X-ray crystal structure determinations from single crystals (Ni) and powder (Mn), magnetic properties, and magnetic structures of the cobalt analogues are reported. The nuclear crystal structures for NaNiH, KNiH, and KMnH are similar to those reported for the cobalt analogues (NaCoH and KCoH) and consist of chains of edge-sharing octahedra (MO(6)) which are connected by H(3)O(2) and SeO(4) to form layers which are in turn bridged by the alkali, in an octahedral coordination site, to form the 3D-framework. The magnetic properties are characterized by antiferromagnetic interaction at high temperatures and antiferromagnetic ordering at low temperatures (NaCoH, 3.5 K; KCoH, 5.9 K; KNiH, 8.5 K; and KMnH, 16 K), except for KNi(2)(H(3)O(2))(SeO(4))(2) which displays a weak ferromagnetic interaction and no long-range ordering above 2 K. The neutron magnetic structures of the cobalt analogues, studied as a function of temperature, are different for the two cobalt salts and also different from all the known magnetic structures of the natrochalcite family. Whereas the magnetic structure of NaCoD has a k = (0, 0, 0), that of KCoD has one consisting of a doubled nuclear cell, k = (0, 0, 1/2). Both compounds have four magnetic sublattices related to the four cobalt atoms of the nuclear unit cell. In NaCoD the moments are in the bc-plane, M(y) = 2.51(2) µ(B) and M(z) = 1.29(4) µ(B), with the major component along the cobalt chain and the resultant moment, 2.83(3) µ(B), making an angle of 27° with the b-axis. The sum of the moments within the cell is zero. For KCoD the moment at each cobalt site has a component along each crystallographic axis, M(x) = 2.40(3), M(y) = 1.03(3), M(z) = 1.59(8) giving a total M = 2.49(3) µ(B). Within one nuclear cell the moments are fully compensated. The moments corresponding to the cobalt atoms of the second nuclear cell comprising the magnetic unit cell are oriented in opposite directions.

Absence of bacterial imprints on struvite-containing kidney stones: a structural investigation at the mesoscopic and atomic scale.

OBJECTIVE: Bacterial imprints are always observed on highly carbonated apatite kidney stones but not struvite kidney stones. Struvite and carbonated apatite stones with a high CO(3)(2-)/PO(4)(3-) rate are believed to develop from infections, but their structural differences at the mesoscopic scale lack explanation. METHODS: We investigated 17 urinary calculi composed mainly of struvite or carbonated apatite by Fourier transform infrared, scanning electron microscopy, and powder neutron diffraction techniques. RESULTS: Carbonated apatite but not struvite stones showed bacterial imprints. If the same stone contained both carbonated apatite and struvite components, bacterial imprints were observed on the carbonated apatite but not the struvite part. Moreover, neutron powder diffraction experiments revealed the crystal size of struvite stones were larger than that of carbonated apatite stones (250 ± 50 vs 50 nm). CONCLUSION: Bacterial imprints may appear more easily on kidney stones with small nanocrystals, such as carbonated apatite than with large nanocrystals, such as struvite. This approach may help identify bacteria contributing to stone formation, perhaps with negative results of urine culture.

Existence of two concomitant magnetic structures below T(Néel) for the natrochalcite, NaFe(II)2(H3O2)(MoO4)2.

A comparative study of the magnetic properties and magnetic structures of the natrochalcite, NaFe(2)(D(3)O(2))(MoO(4))(2) (FeD) to those of the isostructural NaCo(2)(D(3)O(2))(MoO(4))(2) (CoD) and NaNi(2)(D(3)O(2))(MoO(4))(2) (NiD) is presented. The structural change is a shrinking of the unit cell in the order of the ionic radii of the transition metal, FeD > CoD > NiD. While NiD and CoD are canted-antiferromagnets with T(N) = 28 and 21 K, respectively, FeD is an anisotropic 2D-Ising antiferromagnet (T(N) = 17 K) with a spin-flop field of 14 kOe at 2 K and the presence of a hysteresis loop reaching only (1)/(4) of the saturation magnetization in 70 kOe. The critical field decreases almost linearly on warming to T(N). The neutron diffraction patterns of FeD below T(N) display numerous magnetic Bragg peaks which cannot be assigned to any one magnetic structure but fits well to two superposed sets, one with a temperature independent line width and has a propagation vector k(1) = (0, 0, 0) while for the other there is a clear dependence and k(2) = (0, 0, ½). In the k(1) = (0, 0, 0) magnetic structure the moments are parallel to each other within one chain and lie along the a-axis but are antiparallel to those in neighboring chains. In contrast CoD and NiD, for which k = (0, 0, 0), have their moments aligned along the b-axis and ac-plane, respectively. The second magnetic structure, k(2) = (0, 0, ½), is characterized by four sublattices, two per layer, where the moments are in the ab-plane and canted with a resultant along the a-axis which is compensated by those of the adjacent layers. For the k(2) = (0, 0, ½) structure, the scattering coherent length decreases, and the moments tend progressively toward the a-axis upon increasing temperature. The coexistence of two concomitant magnetic structures is unprecedented for compounds containing transition metal moment carriers.

Synthesis, magnetic properties, and magnetic structure of a natrochalcite structural variant, KM(II)2D3O2(MoO4)2 (M = Mn, Fe, or Co).

We report the syntheses, crystal structures, and magnetic properties of KMn(2)(H(3)O(2))(MoO(4))(2) (MnH), KMn(2)(D(3)O(2))(MoO(4))(2) (MnD), KFe(2)(H(3)O(2))(MoO(4))(2) (FeH), KFe(2)(D(3)O(2))(MoO(4))(2) (FeD), KCo(2)(H(3)O(2))(MoO(4))(2) (CoH), and KCo(2)(D(3)O(2))(MoO(4))(2) (CoD), and the magnetic structures of MnD and FeD. They belong to the structural variant (space group I2/m) of the mineral natrochalcite NaCu(2)(H(3)O(2))(SO(4))(2) (space group C2/m) where the diagonal within the ac-plane of the latter become one axis of the former. The structure of MnD, obtained from Rietveld refinement of a high-resolution neutron pattern taken at 300 K, consists of chains of edge-sharing octahedra bridged by MoO(4) and D(3)O(2) to form layers, which are connected to K through the oxygen atoms to form the three-dimensional (3D)-network. The X-ray powder diffraction patterns of the other two compounds were found to belong to the same space group with similar parameters. The magnetic susceptibilities of MnH and FeH exhibit long-range ordering of the moments at a Néel temperature of 8 and 11 K, respectively, which are accompanied by additional strong Bragg reflections in the neutron diffraction in the ordered state, consistent with antiferromagnetism. Analyses of the neutron data for MnD and FeD reveal the presence of both long- and short-range orderings and commensurate magnetic structures with a propagation vector of (½, 0, ½). The moments are antiferromagnetically ordered within the chains with alternation between chains to generate four nonequivalent nuclear unit cells. For MnD the moments are perpendicular to the chain axis (b-axis) while for FeD they are parallel to the b-axis. The overall total is a fully compensated magnetic structure with zero moment in each case. Surprisingly, for KCo(2)(D(3)O(2))(MoO(4))(2) neither additional peaks nor increase of the nuclear peaks' intensities were observed in the neutron diffraction patterns below the magnetic anomaly at 12 K which was identified to originate from a small quantity of a ferromagnetic compound, Co(2)(OH)(2)MoO(4).

Hydrogenation inducing ferromagnetism in the ternary antiferromagnet NdCoSi.

The hydride NdCoSiH obtained by exposure at 523 K of the ternary antiferromagnet NdCoSi under a pressure of 4 MPa of hydrogen crystallizes in the tetragonal ZrCuSiAs-type structure where H atoms occupy the tetrahedral [Nd(4)] site. The hydrogenation induces an increase in the unit cell volume close to 6%. The investigation of NdCoSiH by magnetization measurements reveals its ferromagnetic behavior below T(C) = 20.5(5) K. Neutron powder diffraction shows that the T(C) temperature is associated with a ferromagnetic arrangement of the Nd moments (2.3(2) mu(B) at 1.5 K) parallel to the c axis as observed for NdFeSi. The magnetic properties, magnetic structure, and the value of the Nd ordered magnetic moment evidenced for NdCoSiH are discussed using both band structure calculations and a comparison with the behavior of NdCoSi and NdFeSi.

Synthesis, magnetic structure, and properties of a layered cobalt-hydroxide ferromagnet, Co5(OH)6(SeO4)2(H2O)4.

The synthesis and nuclear and magnetic structures from the powder diffraction of Co(II)(5)(OH)(6)(SeO(4))(2)(H(2)O)(4) and its deuterated analogues as well as their infrared spectral, thermal, and magnetic properties are reported. The nuclear structure consists of brucite-like cobalt hydroxide layers connected by ...OSeO(3)-Co(H(2)O)(4)-O(3)SeO... bridges. The two independent cobalt atoms within the layer are arranged in chains along the b axis creating an anisotropy within each layer. The interlayer distance (10.718 A) is the only parameter to increase compared to the sulfate analogue (10.273 A). The infrared spectra and thermal properties are similar to those reported for the sulfate analogue. Due to the ferromagnetic exchange between the nearest-neighbor cobalt atoms within the layer, satisfying the Goodenough-Kanamori rule, and the weak interlayer exchange, an overall ferromagnet is obtained. The ferromagnetic order at 9 K was confirmed by the ac susceptibilities, the saturation magnetization, and most importantly the enhancement of some Bragg diffraction peaks below the Curie temperature. The moments of all the cobalt atoms were found to be aligned along the b axis with a moment of 3.25(8) mu(B) each giving the best fit. The increase in layer distance and the electron density by replacing sulfur by selenium lowers the Curie temperature.

Magnetic properties and magnetic structure of Cu(II)3Mo(VI)2O9.

The magnetic properties and the low-temperature nuclear and magnetic structures of Cu(3)Mo(2)O(9) are reported. It consists of magnetic chains of oxygen-bridged vertex-shared Cu(4) tetrahedra connected into a 3D network by bridging MoO(4). Each chain is a segment of the pyrochlore structure. The magnetic properties are dominated by antiferromagnetic coupling and show a low-dimensional behavior with a broad maximum at 20 K. At 9.5 K, long-range antiferromagnetic ordering with a small canting is observed. The magnetic structure determination from neutron diffraction resolves only the orientations and magnitude (1.0(1) micro(B) per Cu) of the moments of two of the three crystallographically independent atoms. The third appears not to contribute to the long-range ordering. Geometric frustration may be responsible for the randomness. It is a unique antiferromagnet with eight sublattices (two sets of four) in the ac plane, leaving the canting to be only possible along the b axis.

Magnetic properties and magnetic structures of synthetic natrochalcites, NaM(II)2(D3O2)(MoO4)2, M = Co or Ni.

The magnetic properties and magnetic structures from neutron diffraction of two synthetic natrochalcites, NaM(II)2(H3O2)(MoO4)2, M = Co (1Co) or Ni (2Ni), are reported. They are isostructural (monoclinic C2/m) and consist of chains of edge-shared MO6 octahedra connected by mu-O from H3O2(-) and MoO4(2-). These chains form a three-dimensional network with O-H-O, O-Mo-O, and O-Na-O bridging 4, 3, and 4 metal ions, respectively. Both compounds behave as canted antiferromagnets but differ in their behaviors, 1Co showing a broad maximum (28 K) above the Neel transition (21 K) and the canting taking place at 13 K, some 8 K below T(N), while for 2Ni the canting takes place at T(N) (28 K). Analyses of the neutron powder diffraction data shed some light on the geometry of D3O2(-) and suggest antiferromagnetism with a propagation vector k = (0,0,0) with the moments within each chain being parallel but antiparallel to those in neighboring chains. The difference between 1Co and 2Ni is in the orientation of the moments; they are parallel to the chain axis (b-axis) for 1Co and perpendicular to it for 2Ni with a major component along the c-axis and a small one along the a-axis. The heat capacity data peak at 20.9(3) K (1Co) and 25.1(1) K (2Ni). The derived magnetic entropies, following correction of the lattice contribution using the measured data for the nonmagnetic Zn analogue, suggest S = 1/2 for 1Co but is lower than that expected for 2Ni (S = 1). In both cases, only ca. 60% of the entropy is found below the magnetic ordering temperature, suggesting considerable short-range correlations at higher temperatures. While the temperature at which the magnetic diffraction becomes observable coincides with that of at the peak in heat capacity, it is lower than T(N) observed by magnetization measurements in both cases, and there is evidence of short-range ordering in a narrow range of temperature (T(N) +/- 5 K).

Magnetic properties and magnetic structures of Cu3(OD)4XO4, X=Se or S: cycloidal versus collinear antiferromagnetic structure.

We report a comparative study of the magnetic properties of synthetic Cu3(OH)4(SO4)x(SeO4)1-x and the magnetic structures of the parent compounds. All compounds are isostructural and belong to the orthorhombic class of parent compounds. They consist of 3-legged ribbons of edge-sharing copper octahedra connected by micro3-OH and XO4 (X=S or Se). XO4 acts both as one-atom and three-atom bridges to connect seven Cu atoms (six Cu(2) and one Cu(1)) belonging to three neighboring ribbons. The two end members behave as low-dimensional AF with a long-range antiferromagnetic state below 5 (X=S) and 8 K (X=Se); the former shows evidence of a canting. Analyses of the neutron powder diffraction data for X=S were shown to display an ordered magnetic state (k=0 0 0) where the moments of Cu(2) within the two outer legs are collinear and parallel within each leg but antiparallel from each other; the orientation of the moments of Cu(2) is the c axis. In contrast, for X=Se k=approximately 1/7 0 0 and the magnetic structure is cycloidal and transforms progressively from being incommensurate (T>3 K) to commensurate (T

Neutron diffraction and theoretical DFT studies of two dimensional molecular-based magnet K2[Mn(H2O)2]3[Mo(CN)7]2.6H2O.

Exchange mechanisms and magnetic structure in the two-dimensional cyano-bridged molecule-based magnet K2[Mn(H2O)2]3[Mo(CN)7]2.6H2O have been investigated by a combination of neutron diffraction studies on both single crystal and powder samples and theoretical DFT calculations. The experimental spin density has been deduced from a new refinement of previously obtained polarized neutron diffraction (PND) data which was collected in the ordered magnetic state at 4 K under a saturation field of 3 T performed in the C2/c space group, determined by an accurate re-evaluation of the X-ray structure. Positive spin populations were observed on the two manganese sites, and negative spin populations were observed on the molybdenum site, which provides evidence of antiferromagnetic Mo3+-Mn2+ exchange interactions through the cyano bridge. The experimental data have been compared to the results of DFT calculations. Moreover, theoretical studies reveal the predominance of the spin polarization mechanism in the Mo-C-N-Mn sequence, with the antiferromagnetic nature of the interaction being due to the overlap between the magnetic orbitals relative to manganese and molybdenum in the cyano bridging region. The magnetic structure of K2[Mn(H2O)2]3[Mo(CN)7]2.6H2O has been solved at low temperature in zero field by powder neutron diffraction measurements. The structure was found to be ferrimagnetic where the manganese and molybdenum spins are aligned along the axis in opposite directions.

Magnetic structure and magnetic properties of synthetic lindgrenite, Cu3(OH)2(MoO4)2.

Synthetic Cu3(OH)2(MoO4)2 consists of Cu3(OH)2 brucite ribbons of edge-sharing copper octahedra connected by MoO4 into a 3D network as in the mineral, lindgrenite, for all temperatures between 1.5 and 300 K. Each ribbon consists of a triangular connection between two different types of copper atom (Cu(1) and 2 Cu(2)) via mu3-OH. The MoO4 acts both as one- and three-atom bridges to connect six Cu atoms belonging to three adjacent ribbons. The magnetic properties are consistent with those of ferrimagnetic chains, and the resulting moment of each chain is parallel below the long-range magnetic ordering at 13 K. The Curie constant is 0.468(1) emu K mol-1 of Cu; the Weiss temperature is -14.2(2) K, and the saturation magnetization at 2 K in 50 kOe is 0.41 N muB mol-1 of Cu. Analyses of the neutron powder diffraction reveal an ordered magnetic state where the moment of Cu(1) is antiparallel to those of the two Cu(2); all of them point along the a axis without any sign of geometrical frustration. Any degeneracy that may be present because of the triangular topology of the Cu atoms (s = 1/2) appears to be lifted by the distortion from an ideal equilateral geometry of the triangle. The entropy, estimated from the heat capacity measurements, attains 50% of the total of 17.7 J K-1 mol-1, close to that expected for three Cu atoms (3R ln 2), up to the long range ordering temperature, and the remaining is associated with the low dimensionality of the material.