Interrelation of the spin, orbital, and charge degrees of freedom in half-doped manganites

Autor: S. M. Dunaevsky, V. V. Deriglazov
Rok vydání: 2007
Předmět:
Zdroj: Physics of the Solid State. 49:1514-1522
ISSN: 1090-6460
1063-7834
DOI: 10.1134/s1063783407080185
Popis: Based on the double-exchange model in the tight-binding approximation, self-consistent energy-band-structure calculations are carried out for the first time for the orbital and charge ordering in La0.5Ca0.5MnO3-type manganites with 16 Mn ions in the unit cell under the assumption of a linear dependence of the Jahn-Teller splitting of the eg level on the occupancy of each ion. The equilibrium magnetic and orbital configurations are determined by minimizing the total energy with respect to the direction of the local magnetic moments and the orbital states of the Mn ions. The dependence of the splitting on the occupancy favors the stabilization of phases with charge separation. This separation is an important factor determining the magnetic structure of the ground state. The ground state can be an insulating antiferromagnetic structure of the CE or G type or a new ferrimagnetic structure with a magnetization lower than that of a saturated ferromagnet by a factor of 2. The existence and the width of the bandgap in the electronic energy spectrum of the CE phase depend on the ratio between the values of the Hund exchange and the splitting. When the splitting is sufficiently large, the Jahn-Teller effect stabilizes the insulating state. The finite value of the Hund coupling also favors the stabilization of the CE phase for the realistic values of the interionic exchange and the hopping integral of itinerant electrons.
Databáze: OpenAIRE
Externí odkaz: