Curie temperature of the two band double exchange model for manganites

Abstract

We consider two-band double exchange model and calculate the critical temperature in ferromagnetic regime (Curie temperature). The localized spins are represented in terms of the Schwinger-bosons, and two spin-singlet Fermion operators are introduced. In terms of the new Fermi fields the on-site Hund's interactions are in a diagonal form and one accounts for them exactly. Integrating out the spin-singlet fermions we derive an effective Heisenberg type model for a vector which describes the local orientations of the total magnetization. The transversal fluctuations of the vector are the true magnons in the theory, which is a base for Curie temperature calculation. The critical temperature is calculated employing the Schwinger-bosons mean-field theory. While approximate, this technic of calculation captures the essentials of the magnon fluctuations in the theory, and for 2D systems one obtains zero Curie temperature, in accordance with Mermin-Wagner theorem.

arXiv comment14 pages, 9 figures

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Cited by in corpus (4)

• Magnetic Phase Diagrams of Manganites-like Local-Moment Systems with Jahn-Teller distortions
• Effect of Jahn-Teller coupling on Curie temperature in the Double Exchange Model
• Curie temperatures of the concentrated and diluted Kondo-lattice model as a possible candidate to describe magnetic semiconductors and metals
• Phase diagrams of $\mathrm{L}{\mathrm{a}}_{1-\mathrm{x}}\mathrm{C}{\mathrm{a}}_{\mathrm{x}}\mathrm{Mn}{\mathrm{O}}_3$ in Double Exchange Model with added antiferromagnetic and Jahn-Teller interaction