Spin-lattice relaxation of tetravalent protactinium in a cubic crystal
Raubenheimer, Louis Johannes
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https://hdl.handle.net/2142/23979
Description
Title
Spin-lattice relaxation of tetravalent protactinium in a cubic crystal
Author(s)
Raubenheimer, Louis Johannes
Issue Date
1965
Doctoral Committee Chair(s)
Stapleton, H.J.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
spin-lattice relaxation
tetravalent protactinium
cubic crystal
electrostatic crystal potential
actinide ion
Language
en
Abstract
"The paramagnetic relaxation time is investtigated for Pa 4+
in the cubic matrix Cs2 (Zr""Pa)C16 between 1.4°K and 4"".2°K,
using the pulse saturation method. A theory, developed for
materials in which the electrostatic crystal potential is
described by a few crystal field parameters, has been used
quite successfully in predicting the relaxation behavior of
salts containing rare earth ions. It is the purpose of this
study to determine whether, the same theory can be extended to
an actinide ion, where the effects of the spin-orbit interaction
are comparable to the effects' of the crystal field interaction.
Experimental data fit the expression llTl = ADT + CDT9 , with
AD = 3.5 + 0.7 sec -1 deg -1 and C~ = (5.1 + 1.5) x 10 -5 sec -1d eg -9
For the purpose of calculating llTl theoretically, static
. 0 4> o( 6> crystal fl.eld parameters A4 < rand A6 r are used to
predict the corresponding dynamic parameters a: < r
4 > and
a~. Second degree coupling coefficients a~are
treated in terms of a single parameter a~~r2~ which is consid~red
unknown in the calculati6rts, as is the phonon velocity, v. A
comparison of the resulting theoretical expressions for AD and C'
withithe corresponding experimental values rE:!sults in two
non-linear equations in a~ -1 2 0 < 6 > < rand a6 r .
In Appendix A the relaxation behavior of the rare earth
ion, Ho' 3+ , in yttrium ethyl sulphate ~""s treated. Experimental
results show a dependence of l/Tl on the concentration of
holmium ions. This may be explained by assuming the relaxation
to be phonon-limited."
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