Recently it was proposed that the orbital ordering of πx,y∗ molecular orbitals in the superoxide CsO2 compound leads to the formation of spin-1/2 chains below the structural phase transition occuring at Ts1=61~K on cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR) study of this phase in CsO2 powder. The EPR signal appears as a broad line below Ts1, which is replaced by the antiferromagnetic resonance below the N\'{e}el temperature TN=8.3~K. The temperature dependence of the EPR linewidth between Ts1 and TN agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of S=1/2 spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR lineshape, linewidth and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent K=0.48. Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO2, which is, therefore, a unique p−orbital system where such a state could be studied.
@article{arxiv.1508.00789,
title = {One-dimensional quantum antiferromagnetism in the $p-$orbital CsO$_2$ compound revealed by electron paramagnetic resonance},
author = {T. Knaflic and M. Klanjsek and A. Sans and P. Adler and M. Jansen and C. Felser and D. Arcon},
journal= {arXiv preprint arXiv:1508.00789},
year = {2015}
}