Antiferromagnetism and crystalline-electric field excitations in tetragonal NaCeO2

TL;DR

This study explores the magnetic structure and crystalline-electric field excitations in tetragonal NaCeO2, revealing antiferromagnetic order, a mixed-character ground state doublet, and magnetic frustration consistent with a Heisenberg J1-J2 model.

Contribution

It provides detailed characterization of the magnetic and electronic properties of NaCeO2, including neutron scattering analysis and magnetic structure determination, highlighting the role of frustration and anisotropy.

Findings

NaCeO2 exhibits antiferromagnetic order below 3.18 K.

The ground state is a mixed-character J_eff=1/2 doublet.

Magnetic moments are aligned along the c-axis, consistent with a frustrated J1-J2 model.

Abstract

We investigate the crystal structure, magnetic properties, and crystalline-electric field of tetragonal, $I4_1/amd$, NaCeO$_2$. In this compound, Ce$^{3+}$ ions form a tetragonally elongated diamond lattice coupled by antiferromagnetic interactions ($\Theta_{CW} = -7.69$ K) that magnetically order below $T_N = 3.18$ K. The Ce$^{3+}$ $J = 5/2$ crystalline-electric field-split multiplet is studied via inelastic neutron scattering to parameterize a $J_{eff} = 1/2$ ground state doublet comprised of states possessing mixed $|m_z \rangle$ character. Neutron powder diffraction data reveal the onset of $A$-type antiferromagnetism with $\mu=0.57(2)$ $\mu_B$ moments aligned along the $c$-axis. The magnetic structure is consistent with the expectations of a frustrated Heisenberg $J_1$-$J_2$ model on the elongated diamond lattice with effective exchange values $J_1 > 4 J_2$ and $J_1 > 0$.