PSEUDOGAPS, JAHN-TELLER DISTORTIONS, AND MAGNETIC ORDER IN MANGANITE PEROVSKITES

Local spin-density calculations are used to investigate the relationsh ip between lattice distortions, magnetic ordering, and electronic prop erties in manganite perovskites. Lattice distortions are found to open pseudogaps at the middle of the majority spin e(g) manifold, which ar e more directly related to rotations than Jahn-Teller distortion. Beca use the pseudogap is narrow, its effect on transport is strongly depen dant on doping, falling off due to Fermi-level motion as La is replace d 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 an discussed in relati on to the CMR effect.