Optical and ESR investigations of lanthanum aluminates LaMg1−xMnxO19 single crystals with magnetoplumbite-like structure |
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Authors: | F Laville D Gourier AM Lejus D Vivien |
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Institution: | Laboratoire de Chimie Appliquée de l''Etat Solide, LA 302 CNRS, ENSCP 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France |
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Abstract: | New lanthanum aluminates LaMAl11O19 (M2+ = Ni, Co, Mn, Mg1?xMnx, 0 ≤ x ≤ 1), with magnetoplumbite-like structure have been obtained as single crystals. This paper is particularly devoted to the Mn2+ and mixed compounds, which exhibit promising luminescent properties. Several characteristics of the crystals are given. The absorption spectra of the materials, as grown, are assigned to Mn2+ ions in tetrahedral sites. After annealing in air new absorptions attributed to octahedral Mn3+ ions, appear. The ESR spectra of Mn2+ in all these crystals exhibit axial symmetry. For x ≤ 0.25 they arise from isolated Mn2+ ions in slightly distorted tetrahedral sites and reveal a strong disorder effect. For x ≥0.5 the spectra consist of a single line, attributed to clusters of magnetically interacting Mn2+ ions. |
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Keywords: | To whom all correspondence should be addressed |
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