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

TL;DR

This study explores the magnetic ground state and crystal field effects in KCeO$_2$, revealing signatures of magnetic order below 300 mK and discussing an anomalous local mode observed in neutron scattering.

Contribution

It provides the first detailed investigation of magnetic ordering and crystal field levels in KCeO$_2$, highlighting an unexplained local mode and confirming theoretical predictions.

Findings

Magnetic order signatures appear below 300 mK.

Ce$^{3+}$ ions exhibit large crystal field splittings.

An anomalous local mode is observed and discussed.

Abstract

The magnetic ground state and the crystalline electric field level scheme of the triangular lattice antiferromagnet KCeO$_2$ are investigated. Below $T_N =$ 300 mK, KCeO$_2$ 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.