Abstract
Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets have been measured at liquid helium temperatures in ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of the microscopic theory of relaxation rates in the manifold of 24 electron-nuclear sublevels of the lowest non-Kramers doublet and the first excited singlet in the ground multiplet split by the crystal field of symmetry. The one-phonon transition probabilities were computed using electron-phonon coupling constants calculated in the framework of the exchange charge model and were checked by optical piezospectroscopic measurements. The specific features observed in field dependences of the in- and out-of-phase susceptibilities (humps and dips, respectively) at the crossings (anticrossings) of the electron-nuclear sublevels are well reproduced by simulations when the phonon bottleneck effect and the cross-spin relaxation are taken into account.
- Received 5 July 2006
DOI:https://doi.org/10.1103/PhysRevB.74.184421
©2006 American Physical Society