Abstract
The ALaMgMnO6x (A = Ca, Sr, Ba) oxides with cubic perovskite structure have been prepared under high oxygen pressure. From the chemical and thermogravimetric analyses, the extent of oxygen deficiency and the average oxidation state of manganese were estimated. The content of Mn(V) increases with a cation going from Ca to Sr, and to Ba. The magnetic measurements indicated that CaLaMgMnO6x follows the curie-Weiss law with μeff = 3.80 B.M., whereas SrLaMgMnO6x and BaLaMgMnO6x are ferromagnetic. Through EPR study, Mn(VI) in a tetrahedral site and Mn(IV) in an octahedral site have been detected in CaLaMgMnO6x while weak ferromagnetic couplings were observed in SrLaMgMnO6x and BaLaMgMnO6x due to the superexchange interactions between the t2 electrons of Mn(IV) and Mn(V) ions. The evolution of all the physical properties could be explained by the variation of covalent bonding character between Mn–O bond in three compounds; the (Mn–O) bond competing with σ[(A, La)–O] bond becomes stronger with A cation going from Ca to Sr, and to Ba, which enhances the formation of Mn(V) in the perovskite lattice.
| Original language | English |
|---|---|
| Pages (from-to) | 183-192 |
| Number of pages | 10 |
| Journal | High Pressure Research |
| Volume | 13 |
| Issue number | 4 |
| DOIs | |
| State | Published - Mar 1995 |
Bibliographical note
Funding Information:This research is in part supported by (i) the Korean Ministry of Education (l992), (ii) the Korean Science Engineering Foundation (92-25-00-02)a nd (iii) CNRS through the KOSEF-CNRS agreement between the Department of Chemistry of S.N.U. and the Laboratoire de Chimie du Solide du CNRS, Universitt Bordeaux I, where the high pressure experiments have been carried out.
Keywords
- Perovskite
- covalency
- high oxygen pressure
- mixed valence
- oxygen deficiency
- pentavalent manganese ion