Lattice effects on the spin dynamics in antiferromagnetic molecular rings

Abstract

We investigate spin dynamics in antiferromagnetic (AF) molecular rings at finite temperature in the presence of spin-phonon (s-p) interaction. We derive a general expression for the spin susceptibility in the weak s-p coupling limit and then we focus on the low-frequency behavior, in order to discuss a possible microscopic mechanism for nuclear relaxation in this class of magnetic materials. To lowest order in a perturbative expansion, we find that the susceptibility takes a Lorentzian profile and all spin operators ($S^x$, $S^y,S^z$) contribute to spin dynamics at wave vectors $q\ne 0$. Spin anisotropies and local s-p coupling play a key role in the proposed mechanism. Our results prove that small changes in the spatial symmetry of the ring induce qualitative changes in the spin dynamics at the nuclear frequency, providing a novel mechanism for nuclear relaxation. Possible experiments are proposed.

4 pages, 2 figures. to appear in PRB

References in corpus (8)

• Quantum Computing in Molecular Magnets
• Effects of D-strain, g-strain, and dipolar interactions on EPR linewidths of the molecular magnets Fe8 and Mn12
• Spin tunneling via dislocations in Mn-12 acetate crystals
• Dislocation-induced spin tunneling in Mn-12 acetate
• A Distribution of Tunnel Splittings in Mn${}_{12}$-Acetate
• Electron and Nuclear Spin Dynamics in Antiferromagnetic Molecular Rings
• NMR as a probe of the relaxation of the magnetization in magnetic molecules
• Magneto-elastic instability in Molecular Antiferromagnetic Rings

Cited by in corpus (2)

• Theory of severe slowdown in the relaxation of rings and clusters with antiferromagnetic interactions
• Spin dynamics in molecular ring nanomagnets: Significant effect of acoustic phonons and magnetic anisotropies