Muon spectroscopy investigation of anomalous dynamic magnetism in NiI${}_2$

Abstract

We present the results of muon-spin relaxation (${\mu }^{+}$SR) measurements of the van der Waals magnet NiI${}_2$, which probe magnetic phase transitions at $T_{N1}=73$~K and $T_{N2}=60$~K. Supporting density functional theory (DFT) calculations allow the determination of a single muon stopping site whose magnetic environment is consistent with the proposed ground-state magnetic structure. ${\mu }^{+}$SR measurements of the dynamics reveal behavior consistent with spin-wave excitations below $T_{N2}$. In the region $T_{N2}<T<T_{N1}$ the character of the dynamics changes qualitatively, resulting in an unusual region of temperature-independent fluctuations.

7 pages, 3 figures, submitted to PRB, Supplemental material included