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Stapleton, H.J. Bohan, Thomas Lynch 2011-07-08T18:40:42Z 2011-07-08T18:40:42Z 10000-01-01 1968 We present the results of our measurements of the spinlattice relaxation rates of several trivalent rare earth ions, in the temperature range 0.25 - 4.2o K. We analyze these results within the framework of the Kronig-Van Vleck-Orbach theory, the main features of which we derive in a semi-rigorous manner. We used the pulse saturation method, operating at a microwave frequency of 15.5 GHz. Through additional measurements of our own and of others on the same samples at 9 GHz, we were able to check the frequency (or field) dependence of the relaxation rates. The non-Kramers Pr:LaC13 system was bottlenecked in the direct region and hence its relaxation rate was essentially frequency independent. The Kramers system Er:LaC13 showed a direct process frequency dependence which was very close to the fourth power law of Van Vleck; the non-Kramers system Tb:LaC13 had a direct relaxation process which varied with the square of the frequency, a variation close to that predicted. Actually, the Tb:LaC13. system is somewhat unusual in that a crystal field splitting of its ground doublet results in the composition of its two lowest states being a function of the magnitude of the applied field. This situation should result in a fairly strong field dependence for the Raman and Orbach coefficients, a dependence which is observed experimentally. In contrast, no frequency dependence was expected or observed for the Raman and Orbach coefficients for Er:LaC13 , The low temperatures used in these experiments were attained through the use of a helium-three cryostat. The construction of this cryostat and the associated ESR pulse spectrometer are described in some detail. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-08T18:40:42Z No. of bitstreams: 1 1968_bohan.pdf: 5058133 bytes, checksum: b47e7faecf6a64a92d258390ae725552 (MD5) Made available in DSpace on 2011-07-08T18:40:42Z (GMT). No. of bitstreams: 1 1968_bohan.pdf: 5058133 bytes, checksum: b47e7faecf6a64a92d258390ae725552 (MD5) Previous issue date: 1968 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-08T18:40:42Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:33:06-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 6082710 http://hdl.handle.net/2142/25736 en 1968 Thomas Lynch Bohan spin-lattice relaxation trivalent praseodymium terbium erbium anhydrous lanthanum trichloride Spin-lattice relaxation of trivalent praseodymium, terbium, and erbium in anhydrous lanthanum trichloride: Temperature and magnetic field dependence Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.