Reduction of Ordered Moment and Néel Temperature of Quasi-One-Dimensional Antiferromagnets Sr2CuO3 and Ca2CuO3

We report elastic neutron diffraction and muon spin relaxation ( μSR) measurements of the quasi-one-dimensional antiferromagnets Sr2CuO3 and Ca2CuO3, which have extraordinarily reduced TN/J ratios. We observe almost resolution-limited antiferromagnetic Bragg reflections in Sr2CuO3 and obtain a reduced ordered moment size of ∼0.06μB. We find that the ratio of ordered moment size μ(Ca2CuO3)/μ(Sr2CuO3)=1.5(1) roughly scales with their Néel temperatures, which suggests that the ordered moment size of quasi-one-dimensional antiferromagnets decreases continuously in the limit of vanishing interchain interactions.