Search for: All records

Geometric magnetic frustration arises when the geometry of a structure prevents the simultaneous fulfillment of nearest-neighbor antiferromagnetic interactions and is commonly observed in lattices that exhibit a triangular topology, such as those found in the pyrochlore structure. Via a mild hydrothermal route, we have synthesized seven quaternary β-pyrochlore related fluorides AxM2+xM3+(2–x)F6, (A = Cs and Rb; M2+ = Co2+, Ni2+ and Zn2+; and M3+ = V3+ and Fe3+). Crystal structures and compositions were determined using a combination of single-crystal X-ray diffraction and energy-dispersive spectroscopy. After adjusting the reaction conditions, phase pure products of AxM2+xM3+(2–x)F6 were obtained. The magnetic susceptibility and isothermal magnetization data for all seven compounds were collected to interpret the magnetic behavior, which ranged from paramagnetic to antiferromagnetic with and without a ferromagnetic component. We found that the magnetic behavior of the AxM2+xV3+(2–x)F6 pyrochlore structures strongly depends on the presence or absence of unpaired electrons on the M2+ position. The titled pyrochlore compounds, with the exception of the Zn-analog, can be considered frustrated materials, with frustration indices in the range of 6 –13. 

Mild hydrothermal synthesis was employed to grow high-quality single crystals of ternary fluoridohafnates at low temperatures. The series of new materials was characterized using single crystal X-ray diffraction, and the crystal structures for AHfF6 (A= Mg and Sr), A2HfF8 (A= Ba and Pb), Ca5Hf3F22 and Cd2HfF8(H2O)6 are discussed herein. Although some material compositions have similar stoichiometries, all the compositions adopt different structural motifs. A comparison of the crystal structures and synthesis techniques of ternary fluoridohafnates and ternary fluoridozirconates is also reported, and the impact of the subtle changes of synthesis conditions on overall structures is discussed. 

Single crystals of A₃MF₆(A = Rb, Cs; M = Al, Ga) were grown from mixed alkali chloride/fluoride fluxes. The polymorphism of each compound was studiedviaTGA/DSC and high temperature X-ray diffraction.