Magnetic resonance of ring spin clusters

Abstract

Using a quantum-based approach, we modeled the free induction decay signals for ring clusters of finite radius consisting of 6 and 8 particles with spin 1/2. In addition, we modeled a free induction decay signal for a spherical spin cluster by superimposing the ring signals. The current research uses two possible orientations of the spins. The ring plane was assumed to be only parallel or orthogonal to the external magnetic field. The free induction decays curves and their Fourier spectra were calculated both with and without the exchange interaction between the spins. The second and fourth moments of the magnetization response were evaluated by direct theoretical equations. The dependence of relaxation time on the ring radius was found. The exchange interaction was found to cause an increase in the relaxation time of a ring cluster when the exchange is positive, and a decrease in the time when it is negative. At the same time, the results obtained for the spherical cluster model do not show such an effect.