Synthetic routes to colossal magnetoresistance manganites thin films containing unstable or highly volatile metal oxides

Abstract

Listen

Translate article

We demonstrate that the colossal magnetoresistance (CMR) manganites doped with the monovalent cations of the large ionic radius A (A = Na +, K +, Ag +) reveal enhanced sensitivity of the electrical resistance to the magnetic field near the room temperature. The main obstacle to their practical application is severe difficulty of the synthesis, in particular, that of the thin films because of the high volatility or low thermal stability of the oxides of these doping elements. But the preparation of the films in two steps allows for the materials with the superior CMR characteristics. At the first step, epitaxial single phase precursor La 1− x A y MnO 3 (0.3 ≥ x > y) is formed on the single crystal substrate due to the epitaxial stabilization by the single source MOCVD (metalorganic chemical vapor deposition) using thd-complexes. The second step is the isopiestic annealing with the powder mixture determining the high concentration of the volatile oxide in the gas phase resulting in the saturation of La 1− x A x MnO 3 ( x = y) films by the gas phase transport. The film transformations are studied with XRD and HREM. The high magnetoresistance MR and magnetotransmission MT with the linear magnetic field (H) dependence near the room temperature (dMR/dH up to 45%/T, dMT/dH up to 15%/T) are reported.