Electron spin resonance in triangular spin tubes

Abstract

We performed electron spin resonance (ESR) on polycrystalline S = 3/2 compounds consisting of equilateral and non-equilateral triangular spin tubes in CsCrF4 and α-KCrK4, respectively. In CsCrK 4, a gapless spin-liquid ground state was realized at 1.5 K. Linewidth of the ESR spectra dramatically increased below 100 K and appeared to diverge around 50 K although no magnetic long-range order occurred above 1.5 K. Furthermore, temperature dependence of integrated intensity of the ESR spectra indicates that the intrinsic ESR spectra can not be observed below 40 K. On the other hand, in α-KCrK4, successive antiferromagnetic long-range order occurred at TNI = 2.5(1) K and TN2 = 4.0(1) K. ESR spectra slightly change not only around TN2 but also around TN1. We considered that the spin structure in TN1 < T < T N2 may slightly change from the quasi-120° spin structure below TN1.