Calorimetric evidence for localized spin fluctuations in UA1$sub 2$ Page: 2 of 9
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CALORIMETRIC EVIDENCE FOR LOCALIZED
SPIN FLUCTUATIONS IN UAl2
R. J. Trainor and M. B. Brodskv
Argonne National Laboratory, Argonne, IL 60439
and L. L. Isaacs
Argonne National Laboratory and Dept. of Chem.
Engr., The City College of C.U.N.Y., New York, NY 10031
ABSTRACT
We present results of heat capacity measurements
on UAl2 between 1.8 and 400K. The data are compared
with recent resistivity and susceptibility measure-
ments which indicate the existence of localized spin
fluctuations in a narrow 5f band. Below about 50K
the electronic contribution to the heat capacity be-
comes large, equivalent to v z 70 mJ/mole-K2. Below
6K there is an upturn in C/T which is proportional to
T2 log (T/TSF), where TSF = 10.6K is identified as
the spin fluctuation temperature. Extrapolation of
this term to zero temperature yields m*/m t 2 for the
spin-fluctuation mass enhancement. At 300K, UAl2 ex-
hibits more typical metallic behavior, with y z 15
mJ/mole-K2. Data are also presented for nonmagnetic
URh3; at low temperatures C = yT + s T3, with y =
14.5 mJ/mole-K2 and S corresponding to 9D = 336K.
INTRODUCTION
In a large number of actinide intermetallic
compounds which do not order magnetically, the ex-
istence of localized spin fluctuations (l.s.f.) has
been proposed to explain resistivities which have T2
dependences at low temperatures.1,2 In support of
this proposal are susceptibility data which often
show magnetic (i.e., temperature dependent) behavior
at high temperature, but level off or become weakly
temperature dependent at lower temperatures. Thwo
compounds which display these properties and which
have attracted considerable attention recently are
UA12 and PuAl.23
If strong spin fluctuation effects are active in
materials like UAl2 and PuAl2, they may be expected
to manifest themselves in the specific heat, as they
do in He3 at ultralow temperatures.4 Such effects
had not been previously observed in any pure compound.
In this paper the results of measurements on
UAl2 between 1.8 and 400K are presented and are con-
sidered in terms of the l.s.f. model. 'e also pre-
*Work supported by the U. S. Atomic Energy Commission.
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Trainor, R. J.; Brodsky, M. B. & Isaacs, L. L. Calorimetric evidence for localized spin fluctuations in UA1$sub 2$, article, January 1, 1974; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc875802/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.