Antiferromagnetic structure with strongly reduced ordered moment of p-electron in CsO2.

We have performed a powder neutron diffraction study on CsO2, where the unpaired electron withs=1/2in theπ∗orbital of the O2-ion is responsible for the magnetism. The magnetic reflections 0120 and 0121 were observed below the Néel temperature of about 10 K. An antiferromagnetic structure with a propagation vector of (0,12, 0) and magnetic moments parallel to thea-axis is the most plausible. The magnitude of the ordered moment is about 0.2 µB, which is considered to be strongly reduced due to the one-dimensionality of the system. We propose a possibleπ∗orbital order that can explain the obtained magnetic structure, and discuss its relation to the one-dimensionality.