Renormalization Group Approach for the Double Exchange Ferromagnets

• Authors: M. Zapalska , T. Domański
• Languages of publication: EN

Abstracts

EN

The discovery of the colossal magnetoresistance (CMR) in the manganese oxides with perovskite structures T_1 - x DMnO_3 (T = La, Pr, Nd; D=Sr, Ca, Ba, Pb) and its potential technological application motivated theoretical and experimental researchers to study the itinerant ferromagnetism. A first theoretical description of this phenomenon in terms of the double-exchange mechanism was given a long time ago by Zener. In this model, the spin orientation of adjacent Mn-moments is associated with kinetic exchange of conduction e_g electrons. Consequently, alignment of the core Mn-spins by an external magnetic field causes higher conductivity. The Mn ions are considered as localized forming a spin of S = 3/2 and they are coupled to the itinerant electrons by a strong ferromagnetic Hund coupling, J_H > 0. We apply the flow equation technique (nonperturbative method, based on continuous canonical transformation) to the double-exchange model for ferromagnetism described by the Kondo type Hamiltonian. We want to eliminate the interaction term responsible for non-conservation of magnon number and to take into account fermion and magnon degrees of freedom. We express the spin operators of Mn ions via the magnon operators (the Holstein-Primakoff transformation) and investigate the magnon excitation spectrum determined by Green's function.

Keywords

EN

05.10.Cc; 75.47.Gk; 75.30.Et; 75.30.Ds

Discipline

• 75.30.Et: Exchange and superexchange interactions(see also 71.70.Gm Exchange interactions)
• 75.30.Ds: Spin waves(for spin-wave resonance, see 76.50.+g)
• 75.47.Gk: Colossal magnetoresistance
• 05.10.Cc: Renormalization group methods

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2012
• Volume: 122
• Issue: 6
• Pages: 1099-1101

Dates

published

2012-12

Contributors

author

M. Zapalska

• Institute of Physics, M. Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

author

T. Domański

• Institute of Physics, M. Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

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Identifiers

DOI

10.12693/APhysPolA.122.1099