Phase formation, crystal structures and magnetic properties of perovskite-type phases in the system La2Co1z(Mg xTi1-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 °C. The space group symmetry of the structure changes from P 2 1 / n via Pbnm to R 3¯ c 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. XRPD patterns for perovskite compounds along the lines La 2 Co(Mg x Ti 1− x )O 6 and La 2 Co 1+ z (Mg 0.5 Ti 0.5 ) 1− z O 6 . ►Tuning of the oxidation state of Co in the perovskite system La 2 Co 1+ z (Mg x Ti 1− x ) 1− z O 6 , z =0≤ x ≤0.6 and 0≤ x <0.9. ►XANES study of the oxidation state of Co in the perovskite system La 2 Co 1+ z (Mg x Ti 1− x ) 1− z O 6 , z =0≤ x ≤0.6 and 0≤ x <0.9. ►Phase relations in the perovskite system La 2 Co 1+ z (Mg x Ti 1− x ) 1− z O 6 , z =0≤ x ≤0.6 and 0≤ x <0.9. ►Magnetic properties in the perovskite system La 2 Co 1+ z (Mg x Ti 1− x ) 1− z O 6 , z =0≤ x ≤0.6 and 0≤ x <0.9.