NMR study of antiferromagnetic spinel CoCo2O4 in paramagnetic and ordered state

Nuclear magnetic resonance of Co-59 at both the tetrahedral A-site and octahedral B-site in an older generation spinel compound of antiferromagnetic CoCo2O4 (T-N = 34 K) was carried out between T = 1.4 and 300 K to provide additional information on the importance of the local crystal field parameters and electron-electron correlations. From an analysis of the T-independent relaxation rate of Co-59 at the A-site in the paramagnetic state, the super-exchange interaction J between the Co2+ ions at the A-site through intervening O2- and Co3+ ions is estimated to be 0.050 cm(-1) with an exchange frequency omega(e) = 5.9 x 10(10) sec(-1), which can not simply be explained within the framework of the Weiss field. A small experimental value of the spin hyperfine field at the A-site, A(s) = 1.63 x 10(-4)cm(-1), is well understood when the second-order orbital moment due to the spin-orbit interaction is taken into consideration. The energy difference Delta between t(2g) and e(g) orbitals at the A- and B-site in CoCo2O4 is found to be 3.3 x 10(3) cm(-1) and 17.7 x 10(3) cm(-1), respectively.