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. (December 2021)

• Record Type: Journal Article
• Authors: Pchelina, Diana; Sedykh, Vera; Chistyakova, Nataliya; Rusakov, Vyacheslav; Alekhina, Yulia; Tselebrovskiy, Alexey; Fraisse, Bernard; Stievano, Lorenzo; Sougrati, Moulay Tahar
• Is Part Of: Journal of physics and chemistry of solids. Volume 159(2021)
• Publication Date: 2021-12
• Subjects: Perovskites -- Doped lanthanum manganites -- Mössbauer spectroscopy -- Phase separation -- Magnetic properties -- Superparamagnetism; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2021.110268
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Ca- and Sr- doped lanthanum manganese perovskites La0.95 A 0.05 Mn0.98 Fe0.02 O3+δ (A = Ca, Sr) (LCM and LSM) of non-stoichiometric (NS) and stoichiometric (S) compositions were prepared by sol-gel method and investigated by 57 Fe Mössbauer spectroscopy and magnetic measurements. In contrast to non-stoichiometric samples, which contain pure singles phases, a mixture of orthorhombic phases O (PnmaI), O′ (PnmaII) and O′′ (PnmaII*) are detected in samples of stoichiometric compositions. The magnetic data, supported by Mössbauer measurements, show the spontaneous formation of magnetically ordered clusters with sizes in the range 2.5–4.6 nm in all samples. The main differences between the investigated LCM and LSM systems, and in particular the less extended phase separation in LSM-S than in LCM-S is connected to the difference in ionic radii on the doping ions, the influence of the Jahn-Teller effect at the Mn +3 centres and the size distributions of the ferromagnetic clusters. Our results show, for the first time, that the O′′ (PnmaII*) phase is characterized by antiferromagnetic ordering. Graphical abstract: Image 1 Highlights: Ca- and Sr- doped lanthanum manganese perovskites were prepared by sol-gel method. The materials were studied by 57 Fe Mössbauer spectroscopy and magnetic measurements. A O–O″–O′ phase transition path was unveiled on stoichiometric annealed phases. The differences between the two systems are related to the ionic radii of the dopants. The intermediate O″ phase is characterized by antiferromagnetic ordering.