Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets LiYF4:Ho3+ have been measured at liquid helium temperatures in the ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of 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 Ho3+ ground multiplet 5I8 split by the crystal field of S4 symmetry. The one-phonon transition probabilities were computed using electron-phonon coupling constants calculated in the framework of 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 (anti-crossings) of the electron-nuclear sublevels are well reproduced by simulations when the phonon bottleneck effect and the cross-spin relaxation are taken into account.
@article{arxiv.0910.0519,
title = {Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+},
author = {S. Bertaina and B. Barbara and R. Giraud and B. Z. Malkin and M. V. Vanuynin and A. I. Pominov and A. L. Stolov and A. M. Tkachuk},
journal= {arXiv preprint arXiv:0910.0519},
year = {2009}
}