Magnetic properties and signatures of moment ordering in triangular lattice antiferromagnet KCeO$_2$

Abstract

The magnetic ground state and the crystalline electric field level scheme of the triangular lattice antiferromagnet KCeO2 are investigated. Below TN = 300 mK, KCeO2 develops signatures of magnetic order in specific heat measurements and low energy inelastic neutron scattering data. Trivalent Ce 3+ ions in the D 3d local environment of this compound exhibit large splittings among the lowest three 4f 1 Kramers doublets defining for the free ion the J = 5/2 sextet and a ground state doublet with dipole character, consistent with recent theoretical predictions in M. S. Eldeeb et al. Phys. Rev. Materials 4, 124001 (2020). An unexplained, additional local mode appears, and potential origins of this anomalous mode are discussed.