A series of single phase (La1−x Sr1+x ) (Mn0.5Co0.5)O4 (0≤x≤0.40) materials with a tetragonal K2NiF4 structure was prepared by a solid state reaction method at 1400 or 1450 °C with a short period of heating time. Powder X-ray diffraction (XRD) and the Rietveld refinement method were employed for the structural analysis. Unit cell a- and c-axes decrease with increasing amount of Sr substitution. A discrepancy between the zero-field-cooled and the field-cooled magnetization is observed in all samples investigated below a characteristic temperature, T *, which likely arises from the canted nature of spins or the random freezing of spins. It appears that T * decreases with increasing amount of Sr substitution, which is possibly due to the enhancement of chemical pressure induced by Sr and a corresponding increases of the valence of Mn and/or Co.
Journal of Superconductivity and Novel Magnetism 23(5), pp.721-724