Effect of Jahn-Teller coupling on Curie temperature in the Double Exchange Model

Abstract

We consider the two-band double exchange model for manganites with Jahn-Teller (JT) coupling and explore the suppression of the ferromagnetism because of the JT distortion. The localized spins of the ${\text{t}}_{2g}$ electrons are represented in terms of the Schwinger bosons, and two spin-singlet Fermion operators are introduced instead of the $e_g$ electrons' operators. In terms of the new Fermi fields the on-site Hund's interaction is in a diagonal form and one accounts for it exactly. Integrating out the spin-singlet fermions, we derive an effective Heisenberg model for a vector which describes the local orientations of the total magnetization. The exchange constants are different for different space directions and depend on the density $n$ of ${\text{e}}_g$ electrons and JT energy. At zero temperature, with increasing the density of the ${\text{e}}_g$ electrons the system undergoes phase transition from ferromagnetic phase $(0<n<n_c)$ to A-type antiferromagnetic phase $(n_c<n)$. The critical value $n_c$ decreases as JT energy is increased. At finite temperature we calculate the Curie temperature as a function of electron density for different JT energy. The results show that JT coupling strongly suppresses the spin fluctuations and decreases the Curie temperature.

4 pages, 3 figures

References in corpus (4)

• Ferromagnetic, A-type, and Charge-Ordered CE-type States in Doped Manganites using Jahn-Teller Phonons
• Existence of a novel metallic ferromagnetic phase in models for undoped manganites
• Magnetic Phase Diagrams of Manganites-like Local-Moment Systems with Jahn-Teller distortions
• Curie temperature of the two band double exchange model for manganites

Cited by in corpus (2)

• 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