Sr content on the structure and magnetic properties of La1−xSrxCoO3

Single phase of La1−xSrxCoO3 (LSCO) with 0.1 ≤ x ≤ 0.4 have been prepared by the solid-state reaction method. All samples have the R3¯c symmetry. There is no phase transition detected at the temperature range from 10 to 300 K. The variations of the local bond-lengths of CoO in CoO6 octahedron and lattice parameter ar confirm that hole-doping stabilize the intermediate-spin (IS) state of Co ions. The magnetic phase diagram is well understood in terms of phase separation scenario. Qualitatively, hole-rich ferromagnetic (FM) clusters increasing in size and number with the increase in the concentration of Sr at the expensive of non-FM insulating matrix, and percolating at the vicinity of 0.15, are suggested to explain the onset of FM order and insulator-metal transition. In addition, the values of effective paramagnetic moment μeff also strongly prove the presence of IS spin state of Co in our system. Very small magnetoresistance (MR), 5% with 3 T magnetic field applied, is obtained. This MR response indicates that a distinct mechanism is likely to dominate in LSCO compared to that in mixed-valence manganites.