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Magnetic Ordering (magnetic + ordering)
Selected AbstractsMultifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity, Separation Capability and Three-Dimensional Magnetic Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2008Kunhao Li Abstract Microporous materials [M3(HCOO)6],·,DMF (M,=,Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X-ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ,5,6,Å. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi-fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p-xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic-based process. Three-dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets. [source] ChemInform Abstract: Magnetic Ordering of the R4Sb3 Compounds (R: Pr, Nd, Sm) and of Pr2Nd2Sb3.CHEMINFORM, Issue 22 2010C. Ritter Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Cs+ -Selective Ion Exchange and Magnetic Ordering in a Three-Dimensional Framework Uranyl Vanadium(IV) Phosphate.CHEMINFORM, Issue 16 2007Tatiana Y. Shvareva Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Magnetic ordering of Mn and Ru in (La0.52Ba0.48) (Mn0.51Ru0.49)O3PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007S. Y. Wu The cover picture of the current issue relates to the article by S. Y. Wu et al. [1]. The authors study the crystal structure and magnetic properties of a polycrystalline (La0.52Ba0.48) (Mn0.51Ru0.49)O3 sample. The critical temperatures of Ru and Mn were determined using the temperature dependent peak intensities. Neutron magnetic diffraction measurements show anomalies that are associated with the ferromagnetic ordering of the Mn and Mn/Ru spins, respectively, with the spin magnetic moments (shown as arrows) either parallel or at an inclined angle to the c -axis direction. The corresponding author Sheng Yun Wu is Assistant Professor at the Department of Physics of the National Dong Hwa University in Hualien, Taiwan. His research interests include the study of magnetic properties in perovskite system and spin polarization of closed d-shell nanoparticles. [source] Magnetic ordering of Mn and Ru in (La0.52Ba0.48) (Mn0.51Ru0.49)O3PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007S. Y. Wu Abstract Neutron diffraction, dc magnetization, and ac magnetic susceptibility measurements have been performed to study the magnetic properties of perovskite (La0.52Ba0.48) (Mn0.51Ru0.49)O3. The compound crystallizes into a cubic Pmm symmetry with a lattice constant of a = 3.9661(4) Å at room temperature. Two anomalies, at around 160 and 60 K, can clearly be seen in the ac susceptibility results, with the peak positions for both anomalies shifting to a higher temperature as a dc magnetic field is applied. Neutron magnetic diffraction measurements show that the anomalies that occur at high and low temperatures are associated, with the ferromagnetic ordering of the Mn and the Ru spins, respectively. The ordering temperatures for the Mn and Ru spins were found to be at TC (Mn) , 195 K and TC (Ru) , 80 K, with a saturated moment of ,,z,Mn, = 2.21(5),B for the Mn spins and ,,z,Ru, = 1.00(5),B for the Ru spins. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis, Structural, and Magnetic Characterization of YCrMnO5EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2005José A. Alonso Abstract A new oxide of nominal stoichiometry YCrMnO5 has been prepared in polycrystalline form by wet-chemistry procedures followed by thermal treatments under high-oxygen-pressure conditions. This material has been characterized by X-ray and neutron powder diffraction (NPD), magnetotransport and magnetization measurements. YCrMnO5 is isostructural with RMn2O5 oxides (R = rare earths); its crystal structure has been Rietveld refined from NPD data in the space group Pbam, and it contains infinite chains of(Cr,Mn)4+O6 octahedra sharing edges, linked together by (Mn,Cr)3+O5 pyramids and YO8 units. An important level of cationic disorder has been found between both metallic sites; the refined crystallographic formula is Y[Mn0.47(1)Cr0.53(1)]oct[Cr0.37(1)Mn0.63(1)]pyrO5. The magnetic susceptibility indicates the onset of magnetic ordering below Tc , 85 K; the magnetization isotherms are characteristic of a weakly ferrimagnetic material reaching a net magnetization of0.25 ,B/f.u. for H = 50 kOe. Low-temperature NPD patterns do not exhibit any additional magnetic contribution, confirming that a long-range magnetic ordering is not fully established. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Multifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity, Separation Capability and Three-Dimensional Magnetic Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2008Kunhao Li Abstract Microporous materials [M3(HCOO)6],·,DMF (M,=,Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X-ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ,5,6,Å. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi-fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p-xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic-based process. Three-dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets. [source] Raman scattering studies of the magnetic ordering in hexagonal HoMnO3 thin filmsJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2010Nguyen Thi Minh Hien Abstract We present the results of the temperature dependence of the Raman spectra of hexagonal HoMnO3 thin films in the 13,300 K temperature range. The films were grown on Pt(111)//Al2O3 (0001) substrates using the laser ablation method. In the HoMnO3 thin films, we initially observedseveral broad Raman peaks at ,510, 760, 955, 1120, and 1410 cm,1. These broad Raman peaks display an anomalous behavior near the magnetic transition temperature, and the intensity difference of the Raman spectra at different temperatures shows several pairs of negative and positive peaks as the temperature is lowered below the Néel temperature. Our analyses indicate that all the broad peaks are correlated with magnetic ordering, and we have assigned the origin of all the broad peaks. Purely on the basis of the Raman analysis, we have deduced the Néel temperature and the spin exchange integrals of HoMnO3 thin films. We also investigated the effects of the growth condition on the strongest broad peak at ,760 cm,1, which is related with pure magnetic ordering. This result indicates that the oxygen defect in the HoMnO3 sample has negligible effect on magnetic ordering. Copyright © 2009 John Wiley & Sons, Ltd. [source] High pressure structure of Tb2Ti2O7 pyrochlore at cryogenic temperaturesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007Ravhi S. Kumar Abstract The structure of Tb2Ti2O7 pyrochlore was investigated at high pressures up to 24 GPa at cryogenic temperatures down to 6.5 K using angular dispersive X-ray diffraction with synchrotron radiation at HPCAT, Advanced Photon Source. The cell parameters were obtained by performing full profile Rietveld refinements of the diffraction data. The equation of state is obtained at low temperatures by fitting the pressure-volume data to a second order Birch Murnaghan eqation and a bulk modulus value of 168(4) GPa is obtained. The results show persistance of the pyrochlore structure up to the maximum pressure studied in the experiment and further indicate that pressure induces solely magnetic ordering which do not involve crystal symmetry changes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Resonant X-ray scattering in the presence of several anisotropic factorsACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2000E. N. Ovchinnikova The general form of the X-ray susceptibility tensor near absorption edges is found when several anisotropic factors, such as the anisotropy of local atomic environment, magnetic ordering and orbital ordering, simultaneously exist in a crystal. Different phenomenological approaches are used to obtain the explicit form of the susceptibility tensor and to find the contributions from each anisotropic factor separately as well as `combined' terms owing to their simultaneous existence. The results of the theoretical treatment are applied to the resonant diffraction by La0.5Sr1.5MnO4 below the Néel temperature, where charge and orbital ordering coexist with anisotropy of local atomic environment and magnetic ordering. [source] Ternary fluorides BaMF4 (M = Zn, Mg and Mn) at low temperaturesACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2009Jose Maria Posse Ternary fluorides BaMF4 (M = Zn, Mg, Mn) have been studied in the temperature range from 300 to 10,K using synchrotron and laboratory powder and single-crystal diffraction. The first two compounds are stable down to 10,K, while the third one undergoes a phase transition to an incommensurately modulated structure at approximately 250,K. The modulated phase is stable down to 10,K. The magnetic anomalies at 45 and 27,K observed previously in BaMnF4 are exclusively reflected in the behavior of the , component of the q vector, which assumes an irrational value of approximately 0.395,Å,1 at the temperature corresponding to the onset of the magnetic ordering and then stays constant down to 10,K. Mn,Mn distances do not indicate any structural response to the magnetic ordering. The formation of the modulated phase can be explained on the basis of simple geometrical criteria. The incorporation of the large Mn cation in the octahedral sheets implies an increase of the cavity in which the Ba ion is incorporated. This leads to the formation of the modulated structure to adapt the coordination sphere around Ba in such a way that the bond-valence sums can be kept close to the ideal value of two. With further lowering of the temperature, the charge balance around the Ba ion requires an increasingly anharmonic character of the modulation function of Ba, until finally at 10,K a crenel-like shape is assumed for the modulation of this atom. [source] Structural behaviour of synthetic Co2SiO4 at low temperaturesACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2008Andrew Sazonov Synthetic Co2SiO4 has an olivine structure with isolated SiO4 groups (space group Pnma) and shows magnetic ordering below 50,K. Single-crystal neutron diffraction was applied to determine precise crystal structure parameters at low temperatures. No structural phase transition was revealed in the temperature range 2.5,300,K. Lattice parameters were determined by high-resolution X-ray powder diffraction between 15 and 300,K. There is a clear evidence of an anomalous thermal expansion related to the magnetic phase transition which can be attributed to magnetostriction. [source] Temperature-dependent crystal structure refinement and 57Fe Mössbauer spectroscopy of Cu2Fe2Ge4O13ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007Günther J. Redhammer The germanate compound Cu2Fe2Ge4O13, dicopper diiron germanate, was synthesized by solid-state reaction at 1403,K and ambient pressure. There is no change of space-group symmetry between 10 and 900,K. Between 40,K and room temperature the a lattice parameter shows a negative thermal expansion which can be connected to a decreasing Cu,Cu interatomic distance. Above room temperature all the lattice parameters are positively correlated with temperature. Among the structural parameters several alterations with temperature occur, which are most prominent for the distorted Fe3+ octahedral site. Besides an increase of the average bond length and of the interatomic Fe,Fe distances, distortional parameters also increase with temperature, while the average Cu,O bond length remains almost constant between 100 and 900,K, as do the average Ge,O distances. 57Fe Mössbauer spectroscopy was used to detect long-range magnetic ordering in Cu2Fe2Ge4O13. While around 100,K, which is the temperature at which a broad maximum is observed in the magnetic susceptibility, no magnetic ordering was detected in the Mössbauer spectrum, below 40,K a narrow split sextet is developed which is indicative of a three-dimensional magnetic ordering of the sample. [source] Electronic structure of BaFe2As2 as obtained from DFT/ASW first-principles calculationsANNALEN DER PHYSIK, Issue 8 2010U. Schwingenschlögl We use ab-initio calculations based on the augmented spherical wave method within density functional theory to study the magnetic ordering and Fermi surface of BaFe2As2, the parent compound of the hole-doped iron pnictide superconductors (K,Ba)Fe2As2, for the tetragonal I4/mmm as well as the orthorhombic Fmmm structure. In comparison to full potential linear augmented plane wave calculations, we obtain significantly smaller magnetic energies. This finding is remarkable, since the augmented spherical wave method, in general, is known for a most reliable description of magnetism. [source] catena -Poly[[diaquamanganese(II)]-di-,-1,1,3,3-tetracyano-2-ethoxypropenido-,4N1:N3]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2003John A. Schlueter The crystal structure of the title compound, [Mn(C9H5N4O)2(H2O)2], conventionally denoted Mn(EtO-TCA)2(H2O)2, where EtO-TCA is 2-ethoxy-1,1,3,3-tetracyanopropenide, is described. The EtO-TCA anions bridge MnII centers through one of the nitrile N atoms of each of their two dicyanomethanide groups, thus forming dibridged chains along ab. These chains are linked into two-dimensional sheets through hydrogen bonding. The seven-atom bridge, which results in a long Mn,Mn intrachain interaction [9.0044,(4),Å], as well as the large interchain separations [8.3288,(4) and 8.5220,(4),Å] prohibit long-range magnetic ordering down to temperatures as low as 1.55,K. [source] | |||||||||||||