Antiferromagnetism and crystalline-electric field excitations in tetragonal NaCeO2

We investigate the crystal structure, magnetic properties, and crystalline-electric field of tetragonal, $I{4}_1\mathrm{/}amd$, NaCeO${}_2$. In this compound, Ce${}^{3+}$ ions form a tetragonally elongated diamond lattice coupled by antiferromagnetic interactions (${\mathrm{\Theta }}_{CW}=-7.69$ K) that magnetically order below $T_N=3.18$ K. The Ce${}^{3+}$ $J=5\mathrm{/}2$ crystalline-electric field-split multiplet is studied via inelastic neutron scattering to parameterize a $J_{eff}=1\mathrm{/}2$ ground state doublet comprised of states possessing mixed $\mathrm{\mid }{m}_z⟩$ 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 $J_1>4J_2$ and $J_1>0$.