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 CsMn3F6(SeO3)(2). By combining dc and ac magnetic susceptibilities, specific heat, electron spin resonance (ESR), and muon spin relaxation (mu SR), we identify two characteristic temperatures T* = 8 K and T = vertical bar Theta(CW)vertical bar = 49(1) K, thereby three distinct regimes: a paramagnetic, a cooperative paramagnetic, and a quasistatic ordered state. At high temperature (T > vertical bar Theta(CW)vertical bar), 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 < vertical bar Theta(CW)vertical bar), 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-cl = 20 K (approximate to vertical bar J(cl)vertical bar) in the specific heat and ESR results, suggesting short-range ordering. At low temperatures below T*, the mu 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.