Spin gap behavior in Cu2 Sc2 Ge4 O13 studied using Sc45 nuclear magnetic resonance

We report the results of a Sc45 nuclear magnetic resonance (NMR) study on the quasi-one-dimensional compound Cu2 Sc2 Ge4 O13 at temperatures between 4 and 300 K. This material has been a subject of current interest due to indications of spin gap behavior. The temperature-dependent NMR shift exhibits a character of low-dimensional magnetism with a negative broad maximum at Tmax 170 K. Below Tmax, the NMR shifts and spin lattice relaxation rates clearly indicate activated responses, confirming the existence of a spin gap in Cu2 Sc2 Ge4 O13. The experimental NMR data can be well fitted to the spin dimer model, yielding a spin gap value of about 275 K which is close to the 25 meV peak found in the inelastic neutron scattering measurement. A detailed analysis further points out that the nearly isolated dimer picture is proper for the understanding of spin gap nature in Cu2 Sc2 Ge4 O13.