Dr. José Roberto Iglesias
1. Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
+1
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Academic Career Length
52Years (1975-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications1 November 1997 in Physical Review B
Journal Article
The Kondo lattice model including nearest-neighbor magnetic exchange interactions is studied here in a mean-field approximation describing both the Kondo state and the intersite magnetic correlations. In the case of antiferromagnetic correlations, our model yields a decrease of the Kondo temperature compared to the one-impurity value, giving, therefore, a “revisited” version of the Doniach diagram with a rather flat Kondo temperature in the nonmagnetic case, as observed in several cerium compounds. Our model shows also that short-range magnetic correlations can appear at a temperature clearly larger than the Kondo temperature, as observed in compounds such as CeCu or CeRuSi.
27 February 2003 in Physical Review B
Journal Article
BCB. Coqblin
B. Coqblin
CLC. Lacroix
C. LacroixMGM. A. Gusmão
M. A. GusmãoJosé Roberto IglesiasWe present theoretical results for a Kondo-lattice model with spin- localized moments, including both the intrasite Kondo coupling and an intersite antiferromagnetic exchange interaction, treated within an extended mean-field approximation. We describe here the case of a noninteger conduction-band filling for which an “exhaustion” problem arises when the number of conduction electrons is not large enough to screen all the lattice spins. This is best seen in the computed magnetic susceptibility. The Kondo temperature so obtained is different from the single-impurity one, and increases for small values of the intersite interaction, but the Kondo-effect disappears abruptly for low band filling and/or strong intersite coupling; a phase diagram is presented as a function of both parameters. A discussion of experimental results on cerium Kondo compounds is also given.
5 September 2007 in Physical Review B
Journal Article
NPN. B. Perkins
N. B. Perkins
MNM. D. Núñez-Regueiro
M. D. Núñez-Regueiro
BCB. Coqblin
B. Coqblin
José Roberto IglesiasWe present theoretical results for the underscreened Kondo lattice model with localized spins coupled to a conduction band through a Kondo coupling, , and interacting among them ferromagnetically. We use a fermionic representation for the spin operators and expand the Hamiltonian in terms of bosonic fields. For large values of , we obtain a ferromagnetically ordered solution and a Kondo regime with a Kondo temperature, , larger than the Curie temperature, . This finding suggests a scenario for a coexistence of Kondo effect and ferromagnetic order. In some uranium compounds, such as UTe or , this kind of coexistence has been experimentally observed: they order ferromagnetically with a Curie temperature of order and exhibit a Kondo behavior for . The proposed underscreened Kondo lattice model accounts well for the coexistence between magnetic order and Kondo behavior and yields to a new “ferromagnetic Doniach diagram.”
20 April 2007 in Physical Review Letters
Journal Article
NANoelia Marcano Aguado
Noelia Marcano AguadoJSJ. C. Gómez Sal
J. C. Gómez Sal
JEJ. I. Espeso
J. I. Espeso
JOSE DE TERESAPAP. A. Algarabel
P. A. Algarabel
José Roberto Iglesias +1
We present evidence for the existence of magnetic clusters of approximately 20 Å in the strongly correlated alloy system () based on small angle neutron scattering experiments as well as the occurrence of staircaselike hysteresis cycles at very low temperature (100 mK). An unusual feature is the observation of long-range ferromagnetic order below the cluster-glass transition without any indication of a sharp transition at a Curie temperature. These observations strongly support a phenomenological model where a percolative process connects both magnetic states. The model can account for all the puzzling data previously obtained in this system, providing a new perspective with regard to the magnetic ground state of other alloyed compounds with small magnetic moments or weak ferromagnetism with intrinsic disorder effects.
1 April 2007 in The European Physical Journal Special Topics
Journal Article
CMC. F. Moukarzel
C. F. Moukarzel
SGS. Gonçalves
S. GonçalvesJosé Roberto IglesiasMRM. Rodríguez-Achach
M. Rodríguez-Achach
RHR. Huerta-Quintanilla
R. Huerta-Quintanilla
1 September 2003 in Physica A: Statistical Mechanics and its Applications
Journal Article
José Roberto IglesiasSGS. Gonçalves
S. GonçalvesSPS. Pianegonda
S. Pianegonda
JVJ.L. Vega
J.L. Vega
GAG. Abramson
G. Abramson
About Me
José Roberto Iglesias obtained his undergraduate degree in physics at the Balseiro Institute, Bariloche Atomic Center, Argentina, where he completed a Licenciatura (equivalent to a bachelor's degree) in physics in 1969. He obtained his Ph.D. in physics (Docteur ès Sciences) at the Laboratory of Solid State Physics at the University of Paris Sud, Orsay, France, in 1977. For over forty-five years, he has been involved in teaching, research, and mentoring, as well as leading research groups on condensed matter physics and complex systems. He has more than 160 publications, an H-index of 24, and over 1200 citations. In recent years, he has been dedicated to the study of interdisciplinary problems, primarily physics applied to economics and social sciences, investigating issues such as income distribution, opinion propagation, epidemics, criminality, and risk propagation in complex networks. He also has extensive experience in the areas of condensed matter physics and statistical physics, mainly working on the Kondo effect, Kondo networks, strongly correlated magnetism, as well as magnetic domains and cellular systems. In August 2019, UFRGS awarded him the title of Emeritus Professor.