Magnetic properties of Co2+ ions in tetrahedral interstices of an oxide lattice

The magnetic properties of Co2+ ions in tetrahedral environment are discussed in relation to published optical data. It appears that the singlet ground state 4F(Γ2)is responsible for a magnetic moment close to the spin-only value, while the 4F (Γ5) level about 4000 cm−1 above this singlet gives rise to a temperature-independent paramagnetic term of ≈ 0.5 × 10−3 erg. G−2 · mole−1. The expected departure from the Curie-Weiss law is demonstrated by susceptibility measurements on mixed crystals of CoO with ZnO, CoAl2O4 with ZnAl2O4 and CoAl2O4 with MgAl2O4 between 300° and 1200°K. The magnetic properties of Co2+ in tetrahedral interstices are compared with those of Co2+ ions in octahedral surroundings.