Doping of the Mn-site in Ln1-yAyMn1-xMxO3 manganites has been extensively investigated. For the manganites exhibiting a Curie temperature (TC) these substitutions depress TC. However, the effect on TC is doping-element dependent. It decreases from dTC/dx = -25 K %-1 for M = Fe down to dTC/dx ∼ 0 K %-1 for M = Cr in the series Sm0.56Sr0.44Mn1-xMxO3. The peculiar role of chromium doping is also shown in the case of the charge-ordered Ln0.5Ca0.5MnO3-substituted manganites that are characterized by low average cationic size on the A-site and cationic size mismatch. For the latter, metal-insulator transitions together with CMR properties are induced by Cr and to a smaller extent by Co and Ni. The hindering of the charge-ordering establishment by these 'impurity effects' is also observed in the case of the two-dimensional manganites La0.5Sr1.5MnO4 and LaSr2Mn2O7. The highest efficiency of Cr among all doping elements may be ascribed to the similar t3 2g electronic configurations of Cr3+ and Mn4+ which allow a double-exchange between the Cr3+ and Mn3+ species.
|Number of pages||25|
|Journal||Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|
|Publication status||Published - 15 Jul 1998|
- Mn-site doping