K. W. Krämer, H. U. Güdel, P. Fischer and L. Keller

**Magnetic order in CeI**_{2}

*Appl. Phys. A* __74__, S595-S597 (2002)

**Abstract:**
CeI_{2} is a halide with metallic conductivity according to the formula
(Ce^{3+})(I^{–})_{2}(e^{–}). Magnetic
interactions are mediated by the conduction electrons and are significantly
stronger than for insulating rare-earth halides. CeI_{2} crystallizes in
the MoSi_{2} layer-type structure with space group I4/mmm and lattice
parameters a=3.87212(5) Å and c=13.8646(2) Å at 15 K. At
T_{N}=10.0(2) K, a phase transition to a 3D antiferromagnetically
ordered state occurs with an incommensurate **k** vector of (0,
0.2761(1), 1) at 1.5 K. The **k** vector is temperature-dependent and,
as the sublattice magnetization, reaches saturation below 4 K. CeI_{2}
has one magnetic sublattice with moments parallel to the a axis. The amplitude
is sine-modulated along the b axis and amounts to 1.87(1) m_{B} per
Ce^{3+} ion. The crystal-field splitting reduces the ordered moment
slightly below the ^{2}F_{5/2} free-ion value of g·J=15/7 for
Ce^{3+}.