The features of structural transformations in lanthanum manganites La1−xAxMnO3+δ (A = Ca, Sr, Ba)

Abstract

Abstract. In this work, the effect of the ionic radius and concentration of a doping element on the features of the structural transformations in polycrystalline lanthanum manganites, La 1-x A x MnO 3+ (A = Ca, Sr, Ba), has been studied by Mössbauer spectroscopy and X-ray diffraction analysis. For Mössbauer investigations, a small amount of 57 Fe (2 at%) Mössbauer isotope was introduced into the samples. It follows from the analysis of the obtained data that both common features of the structural transformations and differences between them exist in lanthanum manganites depending on ionic radius and concentration of a doping element.

Alkaline-earth metal-doped perovskites La0.95A0.05MnO3+δ (A = Ca, Sr): New structural and magnetic features revealed by 57Fe Mössbauer spectroscopy and magnetic measurements

“…The crystal structure of all samples was determined by X-ray diffraction (XRD) in previous works [10,11,14]. The LCM-NS and LSM-NS samples studied in this work are rhombohedral (space group R-3c).…”

“…The emergence of Mn 4+ leads to a structural change: the PnmaII phase begins to transform into the high symmetry PnmaI phase via the PnmaII* intermediate. One should note that it is difficult to discriminate the three orthorhombic phases by XRD in a mixture of stoichiometric low-doping LAM since their patterns are very close to each other [14].…”

“…The lattice parameters for the R-3c and PnmaII* phases of La 0.95 A 0.05 Mn 0.98 Fe 0.02 O 3+δ (A = Sr, Ca) of non-stoichiometric and stoichiometric compositions[14]. For comparison, the data for R-3c and PnmaII phases of the parent LaMnO 3+δ with 1.5 at% 57 Fe Mossbauer isotope are listed as well.…”