A new pyrochlore compound, NaCaNi2F7, was recently synthesized and has a single magnetic site with spin-1 Ni2+. We present zero field (ZF) and longitudinal field (LF) muon spin rotation (μSR) 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-μ-F muon spin polarization function is observed at high temperatures where Ni spin fluctuations are sufficiently rapid. The Ni2+ 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.
@article{arxiv.1806.10970,
title = {$\mu$SR study of spin freezing and persistent spin dynamics in NaCaNi$_2$F$_7$},
author = {Y. Cai and M. N. Wilson and A. M. Hallas and L. Liu and B. A. Frandsen and S. R. Dunsiger and J. W. Krizan and R. J. Cava and Y. J. Uemura and O. Rubel and G. M. Luke},
journal= {arXiv preprint arXiv:1806.10970},
year = {2018}
}