- Title:
- Sergio Magalhães: Models for Complex Magnetic Systems
- When:
- 24.05.2013 16.00 h
- Where:
- Sala A5-01 - Niteroi
- Category:
- Seminários

O seminário de Mecânica Estatística desta semana (6a feira, 24/05/2013) será apresentado às 16:00h na sala A5-01 do Instituto de Física.

Título: Models for Complex Magnetic Systems

Apresentador: Sergio G. Magalhães (Instituto de Física da UFF)

Resumo:

We discuss the theoretical approaches used to describe the competition among

Kondo effect, spin glass (SG) phase, ferromagnetic (FE) and antiferromagnetic

(AF) order in disordered cerium systems such as CeNi_(1−x)Cu_x and

Ce_2Au_(1−x)Co_xSi_3 . In these approaches, the model used was the Kondo

lattice model with a random exchange interaction Jij between localized f-spins

called here Kondo-Ising model. Firstly, several types of randomness for Jij

were tested as the Sherrington-Kirpatrick, the Hopﬁeld and van Hemmen model for

spin glasses to explain the magnetic part of the experimental phase diagram of

CeNi_(1−x)Cu_x and Ce_2Au_(1−x)Co_xSi_3 [1,2,3]. It should be remarked that for

the van Hemmen type of ramdomness, the disorder can be treated without the use

of the replica method. Then, the Kondo-Ising model was reformulated replacing

f-spins by clusters of f-spins [4]. Finally, a random ﬁeld was added to the

Kondo-Ising model in order to describe some aspects of the experimental phase

diagram of the CeNi_(1−x)Cu_x [5].

[1] A. Theumann, B. Coqblin, S. G. Magalhaes, A. A. Schmidt, Phys. Rev. B 63

(2001) 054409.

[2] S. G. Magalhaes, F. M. Zimmer, P. R. Krebs, B. Coqblin, Phys. Rev. B 74

(2006) 014427.

[3] S. G. Magalhaes, F. M. Zimmer, B. Coqblin, Phys. Rev. B 81 (2010) 094424..

[4] F. M. Zimmer, S. G. Magalhaes, B.Coqblin, Physica B 404/19 (2009) 2972.

[5] S. G. Magalhaes, F. M. Zimmer, B. Coqblin, J. Magn. Magn. Mat. 339 (2013)

30.

- Group:
- Sala A5-01
- Street:
- Instituto de Física da UFF
- ZIP:
- 24210-346
- City:
- Niteroi
- State:
- RJ
- Country:

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