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The van Hemmen-Kondo model for disordered cerium systems
S G Magalhaes1, F M Zimmer, B Coqblin
1Instituto de Fisica, Universidade Federal Fluminense, Avenida Gal Milton tavares de Souza s/n, 24210-346, Niterói, Rio de Janeiro, Brazil.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|February 23, 2011
Summary
Disordered cerium alloys exhibit complex magnetic behaviors. The van Hemmen-Kondo model explains transitions between Kondo, spin glass, and ferromagnetic phases, improving theoretical descriptions of these systems.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Statistical Mechanics
Background:
- Disorder and strong correlations in cerium alloys (e.g., Ce(Ni, Cu)) present complex magnetic phenomena.
- Previous studies observed transitions from spin glass to ferromagnetism and Kondo phases in Ce(Ni, Cu) alloys, with recent findings indicating magnetic clusters.
Purpose of the Study:
- To theoretically investigate the competition between the Kondo effect, spin glass (SG), and ferromagnetic (FE) ordering in disordered cerium systems.
- To present results from the van Hemmen-Kondo model for a more accurate description of these complex magnetic interactions.
Main Methods:
- Theoretical modeling using the van Hemmen-Kondo model, incorporating ferromagnetic interactions and site-disorder randomness.
- Mean-field approximation for the Kondo effect and established models (Sherrington-Kirkpatrick, Mattis) for SG behavior were considered.
Main Results:
- The van Hemmen-Kondo model predicts a Kondo phase for strong Kondo exchange (JK).
- For weaker JK, a temperature-dependent succession of phases is observed: spin glass, mixed spin glass-ferromagnetic, and ferromagnetic.
- The model successfully accounts for recent experimental data on disordered cerium systems, including magnetic clusters.
Conclusions:
- The van Hemmen-Kondo model offers an improved theoretical framework for understanding disordered Kondo systems.
- This simplified approach facilitates further calculations and better explains experimental observations in cerium alloys.
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