Two stage evolution of magnetic correlations in the spiral spin liquid material Ca10Cr7O28

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 gt; gt; J . In contrast, at low temperatures kBT lt; 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 amp; 8727; amp; 8776; 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 antiferromagne