Spin dynamics in the Van der Waals magnet CrCl${}_3$

Abstract

The magnetic nature of low dimensional compound, CrCl${}_3$, was investigated by muon spin rotation, relaxation and resonance (${\mu }^{+}$SR). The ${\mu }^{+}$SR measurements revealed three distinct phases as a function of temperature: an antiferromagnetic state (AF) for $T\le T_{\mathrm{N}}=14.32(6)$~K, a ferromagnetic short range ordered state (FM-SRO) for $T_{\mathrm{N}}<T<\sim 18$~K and a paramagnetic phase (PM) above $\sim 18$~K. Moreover, the AF state exhibits appreciable spin dynamics, which increases with decreasing temperature below $T_{\mathrm{N}}$. These dynamics originate from out of plane fluctuations, which seem to settle for $9.5$~K$\le T\le T_{\mathrm{N}}$, evidenced from measurements in ZF and complementary local field calculations. Moreover, the presented muon Knight shift measurements just above $T_{\mathrm{N}}$ represent a clear microscopic evidence for the absence of the previously speculated long range quasi-2D FM order.

6 pages, 4 figures