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

Abstract

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