NMR relaxation in the diluted one-dimensional Heisenberg antiferromagnets

Abstract

Proton NMR of the diluted one-dimensional Heisenberg antiferromagnets has been observed by the conventional spin echo method in zero magnetic field below the Néel temperature. The temperature dependences of the spin-lattice relaxation rates 1/T1 have been obtained. 1/T1 in a pure system increases rapidly with the increasing temperature, which is attributed to the change of the relaxation mechanism from the two magnon to three magnon processes. A slight dilution caused the spin-lattice relaxation rates increase markedly at low temperatures. But at high temperatures, the temperature dependences of the diluted systems approach that of pure system. The results are discussed on the basis of the spin wave theory. The spin echo intensity decays as a function of the square of the interval time between two pulses. The temperature dependences of the spin-spin relaxation time T2G measured from a Gaussian decay are reported, too.