NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7: novel single crystal pyrochlore antiferromagnets

Abstract

The crystal structures and magnetic properties of three previously unreported A2B2F7 pyrochlore materials, NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7 are presented. In these compounds, either S=2 Fe2+ or S=5/2 Mn2+ is on the B site, while nonmagnetic Na and Ca (Na and Sr) are disordered on the A site. The materials, which were grown as crystals via the floating zone method, display high effective magnetic moments and large Curie-Weiss thetas. Despite these characteristics, freezing of the magnetic spins, characterized by peaks in the susceptibility or specific heat, is not observed until low temperatures. The empirical frustration index, f=- θcw/Tf, for the materials are 36 (NaSrMn2F7), 27 (NaSrFe2F7), and 19 (NaCaFe2F7). AC susceptibility, DC susceptibility, and heat capacity measurements are used to characterize the observed spin glass behavior. The results suggest that the compounds are frustrated pyrochlore antiferromagnets with weak bond disorder. The magnetic phenomena that these fluoride pyrochlores exhibit, in addition to their availability as relatively large single crystals, make them promising candidates for the study of geometric magnetic frustration.

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Cited by in corpus (16)

• Frustrated quantum rare-earth pyrochlores
• The Chemistry of Quantum Spin Liquids
• Quantum and Classical Phases of the Pyrochlore Heisenberg Model with Competing Interactions
• Continuum of quantum fluctuations in a three-dimensional $S=1$ Heisenberg magnet
• Experimental Insights into Ground State Selection of Quantum XY Pyrochlores
• Single-ion properties of the $S_{eff}$ = 1/2 XY antiferromagnetic pyrochlores, Na$A^{\prime }$Co${}_2$F${}_7$ ($A^{\prime }=$ Ca${}^{2+}$, Sr${}^{2+}$)
• Frustrated Magnetism in Fluoride and Chalcogenide Pyrochlore Lattice Materials
• Competing phases and topological excitations of spin-one pyrochlore antiferromagnets
• Six-loop $\epsilon$ expansion study of three-dimensional $O(n)\times O(m)$ spin models
• Real-space investigation of short-range magnetic correlations in fluoride pyrochlores NaCaCo${}_2$F${}_7$ and NaSrCo${}_2$F${}_7$ with magnetic pair distribution function analysis
• $\mu$SR study of spin freezing and persistent spin dynamics in NaCaNi${}_2$F${}_7$
• Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo${}_2$F${}_7$
• Degenerate ground state in the classical pyrochlore antiferromagnet Na${}_3$Mn(CO${}_3$)${}_2$Cl
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• Glassy disordered ground states in the frustrated pyrochlore and fluorite antiferromagnets NaCd$M_2$F${}_7$ ($M$ = Ni${}^{2+}$, Mn${}^{2+}$)