Pseudogaps, Jahn-Teller distortions, and magnetic order in manganite perovskites

Local spin-density calculations are used to investigate the relationship between lattice distortions, magnetic ordering, and electronic properties in manganite perovskites. Lattice distortions are found to open pseudogaps at the middle of the majority spin eg manifold, which are more directly related to rotations than Jahn-Teller distortion. Because the pseudogap is narrow, its effect on transport is strongly dependent on doping, falling off due to Fermi-level motion as La is replaced by divalent ions in LaMnO₃. Structural relaxations provide evidence that unlike pure LaMnO₃, lattice distortions in the ferromagnetically-ordered colossal-magnetoresistance (CMR) regime are relatively weakly coupled to electronic properties. These results are discussed in relation to the CMR effect.