Wikipedia (Cerium is a soft, ductile, silvery-white metallic chemical element with symbol Ce and atomic number 58. Tarnishing rapidly when exposed to air, it is soft enough to be cut with a knife. Cerium is the second element in the lanthanide series, and while it often shows the +3 state characteristic of the series, it also exceptionally has a stable +4 state that does not oxidise water. It is also traditionally considered to be one of the rare earth elements. Cerium has no biological role, and is not very toxic.)
Paramgnet: g = 6/7, J = 5/2, gj = 2.14 BM.
Magnetic structure of cerium has not been fully determined, but it now seems15 that commensurable transverse waves are formed on both the hexagonal and the cubic sites of dhcp beta-Ce, with the magnetic wavevector q in a b-direction and the moments pointing along an a-axis in the plane. The magnetic periodicity is twice that of the lattice. The transition temperatures are T_N=13.7 K for the hexagonal sites and T_N=12.5 K for the cubic sites. Ref: E.P. Gibbons, E.M. Forgan, and K.A. McEwen, J. Phys. F 17, L101 (1987)