Spin dynamics of triangular spin tubes

We performed temperature (T) dependence experiments on the AC magnetic susceptibility of equilateral and non-equilateral triangular spin tubes CsCrF4 and α-KCrF4, respectively. In α-KCrF4, the linear (X0′) and the nonlinear (X2′) magnetic susceptibilities show sharp peaks at 4.0 K, which corresponds to an antiferromagnetic phase transition. On the other hand, in CsCrF4, broad and positive X0′ (T) peaks appear above f = 31 Hz at T ≃ 4 K, but no anomaly of X0′ (T) occurs at f = 31 Hz. Furthermore, the X2′ (T) curve at f = 977 Hz shows a broad and negative peak at T ∼3 K. We suspect that there is a gradual change in spin dynamics below T ≃ 4 K from the paramagnetic state at a high temperature to a slowly-fluctuating spin state without typical antiferromagnetic longrange order as one-dimensionality along the spin tubes coexists with geometrical spin frustration in the equilateral triangular planes.