Phase formation, crystal structures and magnetic properties of perovskite-type phases in the system La2Co1+z(MgxTi1−x)1−zO6

Perovskite-type cobaltates in the system La(2)Co(1+z) (Mg(x)Ti(1-x))(1-z)O(6) were studied for z=0 <= x <= 0.6 and 0 <= x <= 0.9, using X-ray and neutron powder diffraction, electron diffraction (ED), magnetic susceptibility measurements and X-ray absorption near-edge structure (XANES) spectroscopy. The samples were synthesised using the citrate route in air at 1350 degrees C. The space group symmetry of the structure changes from P2(1)/n via Pbnm to R (3) over barc with both increasing Mg content and increasing Co content. The La(2)Co(Mg(x)Ti(1-x))O(6) (z=0) compounds show anti-ferromagnetic couplings of the magnetic moments for the Co below 15 K for x=0, 0.1 and 0.2. XANES spectra show for the compositions 0 <= x <= 0.5 a linear decrease in the L(3)/(L(3)+ L(2))Co-L(2.3) edge branching ratio with x, in agreement with a decrease of the average Co ion spin-state, from a high-spin to a lower-spin-state, with decreasing nominal Co(2+) ion content.