Reduction of Ordered Spin Moments in Antiferromagnets of S = 5/2 Ions (Fe3+, Mn2+) Driven by Local Magnetic Excitation

For antiferromagnets composed of spin five-half ions, the moments of these ions in the ordered antiferromagnetic state can be significantly smaller than 5 BM (i.e., 1.56 - 4.48 BM) if these ions form quantum fluctuating entities (QFEs), for example, quasi one-dimensional uniform antiferromagnetic chains or quasi zero-spin antiferromagnetic spin dimers. It is reasonable to suppose that the stronger the quantum fluctuation in such an antiferromagnet, the greater the reduction in its ordered moment would become, but this supposition has not yet been confirmed because quantifying the strength of quantum fluctuation is not a straightforward matter. Here we show that the local magnetic excitations involving the QFEs can be used to quantify the strength of quantum fluctuation by analyzing six antiferromagnets showing significant reduction in their ordered spin moments.