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arXiv · 1806.10970

$\mu$SR study of spin freezing and persistent spin dynamics in NaCaNi$_2$F$_7$

Y. Cai·M. N. Wilson·A. M. Hallas·L. Liu·B. A. Frandsen·S. R. Dunsiger·J. W. Krizan·R. J. Cava·Y. J. Uemura·O. Rubel·G. M. Luke
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Abstract

A new pyrochlore compound, NaCaNi$_2$F$_7$, was recently synthesized and has a single magnetic site with spin-1 Ni$^{2+}$. We present zero field (ZF) and longitudinal field (LF) muon spin rotation ($\mu$SR) measurements on this pyrochlore. Density functional theory (DFT) calculations show that the most likely muon site is located between two fluorine ions, but off-centre. A characteristic F-$\mu$-F muon spin polarization function is observed at high temperatures where Ni spin fluctuations are sufficiently rapid. The Ni$^{2+}$ spins undergo spin freezing into a disordered ground state below 4~K, with a characteristic internal field strength of 140~G. Persistent Ni spin dynamics are present to our lowest temperatures (75~mK), a feature characteristic of many geometrically frustrated magnetic systems.

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Y. Cai, M. N. Wilson, A. M. Hallas, L. Liu, B. A. Frandsen, S. R. Dunsiger, J. W. Krizan, R. J. Cava, Y. J. Uemura, O. Rubel, G. M. Luke. 2018-06-28. $\mu$SR study of spin freezing and persistent spin dynamics in NaCaNi$_2$F$_7$. https://doi.org/10.1088/1361-648x%2Faad91c

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