Effects of Geometrical Spin Frustration on Triangular Spin Tubes Formed in CsCrF4 and α-KCrF4

Abstract

We conducted X-ray diffraction, magnetic susceptibility, heat capacity, high-field magnetization, and electron spin resonance experiments on high-quality polycrystalline S =3/2 compounds consisting of equilateral and non-equilateral triangular spin tubes in CsCrF 4 and α-KCrF 4 , respectively. In both compounds, geometrical spin frustration in the triangular planes coexists with one-dimensionality along the tubes. In CsCrF 4 , no magnetic long-range order appeared above 1.5 K, which agrees with a prior report [H. Manaka et al. : J. Phys. Soc. Jpn. 78 (2009) 093701]. In a low temperature ( T ) regime, T -linear component of heat capacity appeared and magnetization curves showed finite initial slopes. As a result, CsCrF 4 consists of a gapless spin-liquid state encompassing resonating spin-singlet pairs not only in each equilateral triangle but also along the tubes. In contrast, for α-KCrF 4 , successive magnetic phase transitions occurred at T N1 = 2.5(1) K and at T N2 = 4.0(1) K because superexchange inte...