but [101]-oriented on NdGaO3 or LaAlO3. Similar results were obtained with Pr05Ca05MnO3 [41,120] (see Fig. 12), Pr07Sr03MnO3 [45], or Pr07Sr0.3—xCaxMnO3 [26]. It seems that this orientation can be generalized for every compound that crystallizes in an orthorhombic structure. This dependence on the orientation with the substrate is explained by the lattice mismatch (a) which should favor one orientation [121]. Indeed, the mismatch between the film and the substrate can be evaluated using the formula a = 100 * (aS — ap)/aS (where aS and aF respectively refer to the lattice parameter of the substrate and the film). For Pr0.5Ca0.5MnO3, the smaller mismatch on LaAlO3 is obtained for the [010]-axis in the plane (aLAO = —0.4%), that is, the [101]-axis perpendicular to the substrate plane. In contrast, the smaller mismatch on SrTiO3 (aSTO = 2.2%) found for the [101]-axis is in the plane and thus the [010]-axis normal to the surface of the substrate as found experimentally [121].

0 0

Post a comment