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

We report elastic neutron diffraction and muon spin relaxation ({mu}SR) measurements of the quasi-one-dimensional antiferromagnets Sr{sub 2}CuO{sub 3} and Ca{sub 2}CuO{sub 3}, which have extraordinarily reduced T{sub N}/J ratios. We observe almost resolution-limited antiferromagnetic Bragg reflections in Sr{sub 2}CuO{sub 3} and obtain a reduced ordered moment size of {approximately}0.06{mu}{sub B}. We find that the ratio of ordered moment size {mu}(Ca{sub 2}CuO{sub 3})/{mu}(Sr{sub 2}CuO{sub 3})=1.5(1) roughly scales with their N{acute e}el temperatures, which suggests that the ordered moment size of quasi-one-dimensional antiferromagnets decreases continuously in the limit of vanishing interchain interactions. {copyright} {ital 1997} {ital The American Physical Society}