Highly dense and compositionally inhomogeneous nano-agglomerates in an epitaxial La 0.8 Sr 0.2 MnO 3 thin film grown on
- PDF / 2,313,878 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 20 Downloads / 191 Views
H.B. Lu, Z.H. Chen, and G.Z. Yang Laboratory of Optical Physics, Institute of Physics & Center for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China (Received 30 July 2004; accepted 12 October 2004)
Microstructures in the thin film of La0.8Sr0.2MnO3 grown on (100) SrTiO3 by laser molecular beam epitaxy were characterized by transmission electron microscopy. Highly dense and dimensionally uniform nano-agglomerates were found embedded in thin film of La0.8Sr0.2MnO3. High-angle angular dark-field imaging, elemental mapping, and compositional analysis revealed that the nano-agglomerates are rich in manganese and poor in lanthanum. The ratio of Mn/La in the nano-agglomerates fluctuates. A salient feature of this compositional fluctuation within the nanoscale is the formation of cubic MnO phase, which appears as the core of the nano-agglomerates. The La0.8Sr0.2MnO3 film is domain-oriented and two domains were identified on the basis of orthorhombic lattice. The orientation relationships between La0.8Sr0.2MnO3 domains and MnO were determined as [010]LSMO,1//[001]MnO and (100)LSMO,1// (110)MnO; [101]LSMO,2//[001]MnO and (010)LSMO,2//(100)MnO. The domain structures and compositional inhomogeneities within nanoscale result in a textured microstructure, which is one of the most important parameters for tuning electronic properties in colossal magnetoresistance oxides. I. INTRODUCTION
Much attention has been paid to the La1−xAxMnO3 (A ⳱ Ca, Sr, Ba) compound family, which has a perovskitebased structure, since the discovery of colossal magnetoresistance (CMR) in these oxides.1–4 Recent observations of large magnetoresistance effects in epitaxial manganite thin films have revived the interest in doped manganite oxides due to potential magnetic random-access memory and read head applications.5,6 Before practical applications are in reality, the critical properties of the CMR oxides must be optimized. Structures and microstructures in these materials are of great importance for understanding the interplay of structure, magnetism, and electronic transport. From the viewpoint of crystallography, three structural polymorphs were identified, 7 ¯ orthorhombic (Pnma), and namely rhombohedral (R3c), monoclinic (P21 /c). All these phases have slightly deformed perovskite structure due to the distortion of the
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0082 J. Mater. Res., Vol. 20, No. 3, Mar 2005
http://journals.cambridge.org
Downloaded: 14 Mar 2015
MnO6 octahedra. Furthermore, microstructural characteristics in thin films of these oxides are generally recognized to be domain-oriented8–12 no matter whether the crystal is orthorhombic or rhombohedral. It is also reported that the crystallographic domain orientation can play a very important part in obtaining magnetic anisotropy.13 Besides crystallographic issues, compositional inhomogeneities are another concern; these are believed to present researchers with an important tool for tuning th
Data Loading...
