Timescale distributions of spin fluctuations in the S=2 kagome antiferromagnet CsMn3F6 ( SeO3)2

Abstract

We report the static and dynamical properties of a newly discovered $S=2$ kagome antiferromagnet ${\mathrm{CsMn}}_{3}{\mathrm{F}}_{6}{({\mathrm{SeO}}_{3})}_{2}$. By combining dc and ac magnetic susceptibilities, specific heat, electron spin resonance (ESR), and muon spin relaxation ($\ensuremath{\mu}\mathrm{SR}$), we identify two characteristic temperatures ${T}^{*}=8$ K and $T=|{\mathrm{\ensuremath{\Theta}}}_{\text{CW}}|=49(1)$ K, thereby three distinct regimes: a paramagnetic, a cooperative paramagnetic, and a quasistatic ordered state. At high temperature ($T>|{\mathrm{\ensuremath{\Theta}}}_{\text{CW}}|$), the ac susceptibility and ESR linewidth show a power-law dependence, reflecting short-range spin-spin correlations of the paramagnetic ${\mathrm{Mn}}^{3+}$ ions. In the cooperative paramagnetic regime (${T}^{*}<T<|{\mathrm{\ensuremath{\Theta}}}_{\text{CW}}|$), the ESR signals evince the development of dichotomic spin correlations, which is interpreted in terms of the distinct timescales of in-plane and out-of-plane spin fluctuations. Remarkably, we observe a broad maximum at the characteristic temperature scale of ${T}_{\text{cl}}=20$ K ($\ensuremath{\approx}|{J}_{\text{cl}}|$) in the specific heat and ESR results, suggesting short-range ordering. At low temperatures below ${T}^{*}$, the $\ensuremath{\mu}\mathrm{SR}$ data suggest the presence of dynamically fluctuating fields with partially frozen moments, consistent with the absence of long-range order evidenced by specific heat and magnetic susceptibility data. A magnetic behavior that depends on the chosen time window points to the presence of multiple timescales and temporally anisotropic spin correlations, as predicted for a classical kagome antiferromagnet.