Abstract
The on single crystals of has been studied in order to investigate the spin-state transition through the nuclear-spin relaxation in this compound. Below the spin-lattice and spin-spin relaxation rates show a thermal-activation-type temperature dependence with an energy gap of ∼180 K. This value is close to the energy difference between the low spin state and the intermediate spin state predicted in the two-stage spin-state transition model with the intermediate spin state. The apparent spin-spin relaxation rates depend on the resonance peaks split due to the nuclear-electric-quadrupole interaction, which is explained by an indirect nuclear spin-spin interaction through the interacting paramagnetic electron spins. This observation is consistent with the ferromagnetic short-range correlation among the electron spins on ions confirmed by neutron-scattering experiments.
- Received 18 November 1999
DOI:https://doi.org/10.1103/PhysRevB.62.410
©2000 American Physical Society