Timescale distributions of spin fluctuations in the S=2 kagome antiferromagnet CsMn3 F6 (SeO3)2

Abstract

© 2022 American Physical Society.We report the static and dynamical properties of a newly discovered S=2 kagome antiferromagnet CsMn3F6(SeO3)2. By combining dc and ac magnetic susceptibilities, specific heat, electron spin resonance (ESR), and muon spin relaxation (μSR), we identify two characteristic temperatures T∗=8 K and T=|ΘCW|=49(1) K, thereby three distinct regimes: a paramagnetic, a cooperative paramagnetic, and a quasistatic ordered state. At high temperature (T>|ΘCW|), the ac susceptibility and ESR linewidth show a power-law dependence, reflecting short-range spin-spin correlations of the paramagnetic Mn3+ ions. In the cooperative paramagnetic regime (T∗<T<|ΘCW|), 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 Tcl=20 K (≈|Jcl|) in the specific heat and ESR results, suggesting short-range ordering. At low temperatures below T∗, the μSR 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.