Experimental study of the physical properties in the complex magnetic phase diagram
of Ce
1 Àx
La
x
RhSn
A. S
´
lebarski
Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla, California 92093-0360
and Institute of Physics, University of Silesia, 40-007 Katowice, Poland
M. Radlowska and T. Zawada
Institute of Physics, University of Silesia, 40-007 Katowice, Poland
M. B. Maple
Department of Physics and Institute for Pure and Applied Physical Sciences, University of California, San Diego, La Jolla,
California 92093-0360
A. Jezierski
Institute of Molecular Physics, Polish Academy of Sciences, 60-179 Poznan ´, Poland
A. Zygmunt
Institute for Low Temperature and Structure Research, Polish Academy of Sciences, 50-950Wroclaw, Poland
Received 1 April 2002; revised manuscript received 12 June 2002; published 30 September 2002
We have investigated the electronic structure and magnetic properties of the new ternary Ce
1-x
La
x
RhSn
system. The 3 d and 4 d x-ray photoelectron spectroscopy XPS spectra indicate a mixed valence of Ce.
Analysis of the 3 d
9
4 f
2
weight in the 3 d XPS spectra using Gunnarsson-Scho ¨nhammer theory suggests a
hybridization interaction of about 120 meV for different compositions x of the system. The magnetic
measurements indicate the existence of a highly anomalous weak ferromagnetic state below 220 K in
Ce
1-x
La
x
RhSn for x 0.6. This ferromagnetism could originate from the ordering of Ce local moments due to
strong Ce 4 f conduction electron hybridization via the Ruderman-Kittel-Kasuya-Yosida RKKY interaction.
The ( T ) and ( T ) data are consistent with non-Fermi liquid behavior for x 0.5, while the magnetic behavior
in the range x 0.5 is dominated by spin fluctuations.
DOI: 10.1103/PhysRevB.66.104434 PACS numbers: 75.20.Hr, 71.27.+a, 72.15.Qm
I. INTRODUCTION
A class of strongly correlated f-electron materials whose
low-temperature physical properties display non-Fermi liq-
uid NFL behavior has attracted a great deal of attention
during recent years.
1–3
The Ce and U ions carry magnetic
dipole or electric quadrupole moments that interact with the
spins and charges of the conduction electrons, giving rise to
a Kondo effect, magnetic and/or quadrupolar ordering, and
NFL behavior at low temperatures. Nonmagnetic elements,
e.g., La, can be substituted on the f-element sublattice, lead-
ing to the NFL regime, presumably through the chemical
disorder. Non-Fermi liquid behavior in f-electron systems is
characterized by weak power law or logarithmic temperature
dependences of the physical properties at low temperatures
T T
0
, where T
0
is a characteristic temperature that, in some
systems, can be identified with the Kondo temperature T
K
.
Theoretical models of the NFL behavior based on single
impurity mechanisms include a multichannel Kondo effect of
magnetic
4,5
or electric origin,
6
and a conventional Kondo ef-
fect with a distribution of Kondo temperatures due to chemi-
cal disorder.
7,8
Theoretical models which incorporate interi-
onic interactions include fluctuations of an order parameter
in the vicinity of a second-order phase transition at 0 K
quantum critical point QCP Refs. 9–15 and an inhomo-
geneous Griffiths’ phase.
16
The Griffiths’ phase
17
consists of
magnetic clusters in a paramagnetic phase, and forms as a
result of the competition between the Kondo effect and the
Ruderman-Kittel-Kasuya-Yosida RKKY interaction in the
presence of disorder. This model
16
predicts C ( T )/ T
( T ) T
-1 +
, where 1 characterizes the Griffiths’
phase.
We recently investigated the compound CeRhSn which
exhibits a NFL behavior.
18,19
The electrical resistivity and
magnetic susceptibility have power law temperature depen-
dences at low temperatures with small exponents ( T )
T
0.75
and ( T ) T
-0.5
, and C ( T )/ T -lnT . However,
the experimental observations show that the NFL behavior in
CeRhSn is accompanied by a very weak magnetic phase
19
which may result from atomic disorder. We suggested that
the NFL behavior observed in CeRhSn may be due to the
proximity of a QCP.
19
In this work, we report the results of a study of the
pseudoternary system Ce
1 -x
La
x
RhSn in which NFL behav-
ior apparently arises from the presence of disorder. In the
range 0 x 0.5, variations in the Ce composition x strongly
reduce the ordering temperature T
f
of the magnetic spin-
glass phase, while for x 0.6, the Ce
1 -x
La
x
RhSn com-
pounds exhibit spin fluctuations.
In the Ce-rich Ce
1 -x
La
x
RhSn compounds ( x 0.5), we
observed a highly anomalous weak ferromagnetic state be-
low T
c
220 K which has the highest magnetic ordering
temperature of any known Ce system with nonmagnetic con-
PHYSICAL REVIEW B 66, 104434 2002
0163-1829/2002/6610/10443410/$20.00 ©2002 The American Physical Society 66 104434-1