Observation of Fluctuation in Dysprosium Nitrate Crystals at Low Temperatures

Fluctuation in the dysprosium nitrate crystal is observed by measuring the time series of ac conductivity at 2 kHz along both the $c$-axis and the direction perpendicular to the $c$-axis below 50 K. The behavior of the fluctuation given in the measurements perpendicular to the $c$-axis is deterministic and metastable. The probability distribution functions (PDFs) derived from the time series data perpendicular to the $c$-axis show an asymmetric non-Gaussian line shape. The width of the PDFs broadens at temperatures below 30 K. The PDFs for the $c$-axis are symmetric Gaussian and normal below 50 K. The anisotropy is found in the structure of the fluctuation at the temperatures below 50 K, and attributed to the quantum properties of dysprosium ions in the nitrate compound.