THEORETICAL-STUDY OF THE DENSITY-OF-STATES AND MAGNETIC-PROPERTIES OFLACOO3

The density of states and magnetic properties of low-spin, high-spin, and mixing states of LaCoO3 have been studied within the unrestricted Hartree-Fock approximation. The real-space recursion method is adopted for computing the electronic structure of the disordered system. The paramagnetic high-spin state is dealt with using the usual binary allo y coherent potential approximation (CPA); an extended trinary alloy CP A approximation is developed to describe the mixing state. In agreemen t with experiments, our results show that the main features of the qua siparticle spectra in the mixing state are not a sensitive function of the high-spin component, but the spectrum does get broadened due to s pin scattering. The increasing of the high-spin component also results in a pileup of the density of states at the Fermi energy which indica tes an insulator to metal phase transition. Some limitations of the pr esent approach are also discussed. [S0163-1829(98)03214-7].