Structure and Magnetism of an Ideal One-Dimensional Chain Antiferromagnet [C 2 NH 8 ] 3 [Fe(SO 4 ) 3 ] with a Large Spin of S = 5/2.

Isolated large-spin Heisenberg antiferromagnetic uniform chain is quite rare. Here, we have successfully synthesized an ideal one-dimensional (1D) S = 5/2 linear-chain antiferromagnet [C 2 NH 8 ] 3 [Fe(SO 4 ) 3 ], which crystallizes in a trigonal lattice with the space group R 3 c . A broad maximum at T max = 18 K is observed in the magnetic susceptibility curve. Notably, no long-range magnetic ordering is observed down to 2 K even if the material has a large Curie-Weiss temperature of θ CW = -25.5 K. High-field magnetization at 2 K shows a linear increase until saturation at 30 T, and a high-field electron spin resonance (ESR) reveals the absence of a zero-field spin gap. The intrachain interaction J and interchain interaction J ' are determined. Quite a small ratio of J '/ J < 2.5 × 10 -3 suggests that [C 2 NH 8 ] 3 [Fe(SO 4 ) 3 ] behaves as an ideal 1D uniform linear-chain antiferromagnet, in which the magnetic ordering is prevented by the extremely small interchain interaction and quantum fluctuation even for a classical spin of S = 5/2.