Electronic structure of zigzag ferromagnetic chains and conditions for the existence of insulating state in manganites

摘要

The tight-binding method and the double-exchange Hamiltonian with infinite on-site Hund interaction are used to calculate the spectrum of e (g) electrons in manganites for various magnetic structures composed of ferromagnetic zigzag spin chains that have two to eight spins per one-dimensional unit cell. The values of the carrier concentration x are found at which the band insulator state can arise in antiferromagnetic manganites La1-x Ca-x MnO3 containing the above chains. In addition to the known spectra of (1 x 1) and (2 x 2) chains, the spectrum of a (3 x 3) zigzag chain is obtained for the first time. A three-dimensional unit cell consisting of this type of chains and having 24 manganese atoms permits a correct qualitative description of the atomic and magnetic structures of the manganite La1/3Ca2/3MnO3.