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  Koo, C.; Park, J.; Werner, J.; Lee, S.; Balz, C.; Islam, A.T.M.N.; Oshima, Y.; Lake, B.; Choi, K.-Y.; Klingeler, R.: Two-stage evolution of magnetic correlations in the spiral spin liquid material Ca₁₀Cr₇O₂₈. Physical Review B 111 (2025), p. 125144/1-7

10.1103/PhysRevB.111.125144
Open Access Version

Abstract:
We present an X-band and tunable high-frequency/high-field electron spin resonance (HF-ESR) study of single-crystalline Ca10Cr7O28, which constitutes alternating antiferromagnetic and ferromagnetic kagome bilayers. At high temperatures, a phonon-assisted relaxation process is evoked to account for the pronounced increase of the linewidth in an exchange-narrowing regime (kBT >> J). In contrast, at low temperatures (kBT < J), a power-law behavior in line narrowing is observed. Our data reveal two distinct power-law regimes for the linewidth which crossover at T∗ ≈ 7.5K. Notably, the intriguing evolution of the ESR linewidth in this alternating kagome bilayer system with opposite sign of exchange interactions highlights distinct spin dynamics compared to those in a uniform kagome antiferromagnet.