NMR observations of level crossings in a Cr8F8 pivalate single crystal: The solution to the structured enhancement of 1/T 1

Abstract

We interpret the novel observations of proton nuclear spin-lattice relaxation rate (1/T1) for a single crystal of the antiferromagnetic ring [Cr8F8(piv)16] in a magnetic field at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72, 020405(R) (2005)]. Diagonalizing a well-equipped microscopic spin Hamiltonian of each cluster and then examining possible intercluster couplings as well, we elucidate why 1/T1 is single-peaked at the first level crossing but double-peaked around the second level crossing.