Synthesis and characterization of La_0.8Sr_1.2Co_0.5M_0.5O_4-? (M=Fe, Mn)

El Shinawi, H.; Marco, J. F.; Berry, F. J. and Greaves, C. (2009). Synthesis and characterization of La_0.8Sr_1.2Co_0.5M_0.5O_4-? (M=Fe, Mn). Journal of Solid State Chemistry, 182(8) pp. 2261–2268.

DOI: https://doi.org/10.1016/j.jssc.2009.06.010

Abstract

The M⁴⁺-containing K₂NiF₄-type phases La_0.8Sr_1.2Co_0.5Fe_0.5O₄ and La_0.8Sr_1.2Co_0.5Mn_0.5O₄ have been synthesized by a sol-gel procedure and characterized by X-ray powder diffraction, thermal analysis, neutron powder diffraction and Mössbauer spectroscopy. Oxide ion vacancies are created in these materials via reduction of M⁴⁺ to M³⁺ and of Co³⁺ to Co²⁺. The vacancies are confined to the equatorial planes of the K₂NiF₄-type structure. A partial reduction of Mn³⁺ to Mn²⁺ also occurs to achieve the oxygen stoichiometry in La_0.8Sr_1.2Co_0.5Mn_0.5O_3.6. La_0.8Sr_1.2Co_0.5Fe_0.5O_3.65 contains Co²⁺ and Fe³⁺ ions which interact antiferromagnetically and result in noncollinear magnetic order consistent with the tetragonal symmetry. Competing ferromagnetic and antiferromagnetic interactions in La_0.8Sr_1.2Co_0.5Fe_0.5O₄, La_0.8Sr_1.2Co_0.5Mn_0.5O₄ and La_0.8Sr_1.2Co_0.5Mn_0.5O_3.6 induce spin glass properties in these phases.

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