抄録
Nuclear magnetic resonance of Co59 in polycrystalline Co3O4 and ZnCo2O4, and Al27 in CoAl2O4 in paramagnetic state was observed. The cobalt signal was identified with the Co3+ ions at the octahedral sites of the spinel structure. The line shift of Co59 in Co3O4 was separated into two terms: temperature-independent and temperature-dependent ones. The temperature-independent shift (1.5%) is interpreted as the second order chemical shift due to the mixing of the low lying excited state. The temperature-dependent shift is attributed to the hyperfine coupling between the cobalt nuclear spin and the electron spins on the Co2+ ions at the tetrahedral sites. The isotropic hyperfine coupling constant A is estimated at 13×10−4 cm−1. The results on ZnCo2O4 and CoAl2O4 give supports to the above interpretations. The line shapes were studied and the thermal relaxation time T1 was estimated to be 1.5×10−5 sec.
