Low energy spin dynamics of a quantum ferrimagnetic chain, NiCu(pba)(H2O)32H2O

Nuclear magnetic resonance (NMR) for 1H nuclei was performed in a Heisenberg chain with alternating spins S=1 and 1/2, NiCu(pba)(H2O)32H2O (pba=1,3-propylenebis (oxamato)) from 4.2 to 280 K. The relaxation rate (1/T1) is proportional to 1/H (H is applied field), whereas the temperature dependence is weak and is almost constant at high temperatures. The temperature and field dependences are investigated on the basis of the spin–wave theory.