Geometrically frustrated systems play an important role in studying new physical phenomena and unconventional thermodynamics. Charge ordered defect pyrochlores F offer a convenient platform for probing the interplay between electron distribution over and sites and structural distortions; however, they are limited to compounds with = V, Fe, Ni, and Cu due to difficulties in the simultaneous stabilization of other 3d elements in the +2 and +3 oxidation states. Herein, we employ Cl anions under hydrothermal conditions for the mild reduction of MnO in concentrated HF to obtain the CsMnMnF composition as a phase pure sample and study its properties.
View Article and Find Full Text PDFA new structure type of composition CeCoGe was grown out of a molten Sn flux. CeCoGe crystallizes in the orthorhombic space group Cmcm, with highly anisotropic lattice parameters of a = 4.3293(5) Å, b = 55.
View Article and Find Full Text PDFUranium(IV) 5f magnetism is dominated by a transition from a triplet to a singlet ground state at low temperatures. For the first time, we achieved magnetic ordering of U(IV) atoms in a complex fluoride through the incorporation of 3 d transition metal cations. This new route allowed us to obtain an unprecedented series of U(IV) ferrimagnetic materials of the new composition CsMUF (M = Mn, Co, and Ni), which were comprehensively characterized with respect to their structural and magnetic properties.
View Article and Find Full Text PDFThe hydrothermal crystal growth of a new uranium phosphite, U(HPO), is reported. This material was found to exhibit optical and magnetic properties not commonly observed in U(IV) containing materials, specifically purple coloration and low temperature magnetism. We discuss the synthesis, structure determination, and characterization of the title compound and comment on its optical, thermal, and magnetic properties.
View Article and Find Full Text PDFA new uranium fluoride phosphate, UFPO, was synthesized via a mild hydrothermal route and characterized optically, thermally, and magnetically. Two thermal transformation products, UO(PO) and UUO(PO), were discovered to be structurally related, and were subsequently synthesized for bulk property measurements. All three materials failed to follow Curie-Weiss behavior at low temperatures, attributed to the nearly ubiquitous singlet ground state of U(IV), transitioning into a Curie-Weiss paramagnetic regime at high temperatures.
View Article and Find Full Text PDFA series of new U(IV) and Th(IV) fluorides, NaUF (1), NaUF (2), NaUF (3), KThF (4), NaThF (5), (HO)ThF (6), and (HO)UF (7), was obtained using hydrothermal and low-temperature flux methods. Mild hydrothermal reactions with uranyl acetate as a precursor yielded 1, 7, and the monoclinic polymorph of NaUF, whereas direct reactions between UF and NaF led to the formation of 2 and orthorhombic NaUF (3). This highlights an unexpected difference in reaction products when different starting uranium sources are used.
View Article and Find Full Text PDFA series of six anti-perovskite fluorides of the type [Cu(H2O)4]3(M1-xM'xF6)2 (where M and M' = V, Cr, Mn, Fe as well as M = Fe and M' = V and Cr) was synthesized as high-quality single crystals via a mild hydrothermal route. These materials belong to a class of perovskite-based structures in which the anions and cations of the regular ABX3 perovskite structure have exchanged positions. Two complex anions, MF6(3-) and M'F6(3-), occupy the normal A and B cation positions, while three complex cations, [Cu(H2O)4](2+), occupy the normally anionic X positions.
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