1998/05/23 by Ryo Maezono, Sumio Ishihara, Naoto Nagaosa
Physics and Astronomy · #cond-mat.str-el
published as Physical Review B, 58, 11 583 (1998). · REVTEX, 14 figures (figure 1 not available electronically).
arxiv created 1998/05/23 · arxiv updated 2009/11/30
We study theoretically the phase diagram of perovskite manganites taking into account the double degeneracy of the eg orbitals in a Mn3+ ion. A rich phase diagram is obtained in the mean field theory at zero temperature as functions of x (hole concentration) and JS (antiferromagnetic interaction between t2g spins). The global features of the phase diagram is understood in terms of the superexchange and double exchange interactions, which are strongly depends on types of the occupied eg orbitals. The strong electron correlation induces the orbital polarization, which controls the dimension of the conduction band. A sequential change of the spin and orbital structures with doping holes is consistent with the recent experiments. In particular, metallic A-type (layered) antiferromagnetic state is found for x∼0.5 with the uniform dx2-y2 orbital ordering. Effects of the Jahn-Teller distortion are also studied. A short version of this paper has been already published (to appear in PRB-rapid June), but this paper contains additional and more detailed results.