The magnetic properties and electronic structure of (LaMnO3)n/(SrTiO3)m superlattices are investigated using the full-scale first principles density functional theory calculations in order to reveal the magnetic ground state and transport of the thin LaMnO3 layers sandwiched by relatively thick SrTiO3 layers. The LaMnO3 layer in the superlattices favors the ferromagnetic metallic state rather than the A-type antiferromagnetic insulator. It is revealed that the strain and asymmetric chemical environment may induce tiny magnetic moment to Ti ions of the SrTiO3 layer near the interface. The possible mechanism for these phenomena is discussed.

So far available experimental data on the magnetic ground state and transport behaviors of CaCrO3 are conflicting, suggesting that the electronic structure may be fragile against intrinsic or external perturbations. In this work we perform full-scale first principles calculations on the magnetic ground state and electronic structure of CaCrO3. It is revealed that the electronic structure and spin order are sensitive to the on-site Coulomb interaction and lattice distortion. The magnetic ground state is of the marginal stability, close to the boundary between various antiferromagnetically ordered phases. A crossing over the magnetic boundaries and associated metal-insulator transitions can be allowed by even weak lattice distortion (compressive strain) on the ab plane. The numerical results suggest that the on-site Coulomb interaction and lattice distortion represent two major ingredients of physics to determine the magnetic ground state, thus reasonably interpreting the scattered experimental data on the spin order and transport behaviors for CaCrO3.