Uniaxial magnetic anisotropy induced by vicinal surfaces in half metallic La 0.7 Sr 0.3 MnO 3 thin films
- PDF / 424,007 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 9 Downloads / 183 Views
1198-E01-04
Uniaxial magnetic anisotropy induced by vicinal surfaces in half metallic La0.7Sr0.3MnO3 thin films P. Perna1, E. Jiménez2, F. J. Terán1, L. Méchin3, J. Camarero1,2 and R. Miranda1,2 1
Instituto Madrileño de Estudios Avanzados en Nanociencia IMDEA-Nanociencia, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain 2 Departamento de Física de la Materia Condensada and Instituto “Nicolás Cabrera”, Universidad Autónoma de Madrid, 28049 Madrid, Spain 3 GREYC-ENSICAEN and Université de Caen-Basse Normandie, Bd. de Marèchal Juan, 14050 Caen, France ABSTRACT We present a detailed study of the angular dependence of the magnetization reversal at room temperature of well characterized epitaxial La0.7Sr0.3MnO3 (001) thin films grown onto SrTiO3 (001) vicinal substrates. The step edges at the substrate surface promote a topological modulation of the films along the step direction, breaking the four-fold magneto crystalline symmetry and favoring a two-fold magnetic anisotropy term. The competition between the biaxial and uniaxial anisotropy is depicted within the framework of the current theory, resulting in a vanishing biaxial contribution. The films hence show the magnetization easy (hard) direction parallel (perpendicular) to the steps direction. The thickness-dependent of both anisotropy and magnetization reversal are discussed in terms of topographic changes. INTRODUCTION The magnetic properties of half-metallic ferromagnetic La0.7Sr0.3MnO3 (LSMO) films are known to be very sensitive to both crystallographic and morphological variations [1-4]. For (001)-oriented LSMO the strain imposed by the lattice mismatch between the film and the substrate can determine the magnetization easy-axis orientation, i.e., magnetic anisotropy. In general, in-plane compressive strain enhances out-of-plane magnetization, whereas in-plane tensile strain increases the in-plane magnetization component. In addition, preferential morphology shapes, produced by patterning or by using vicinal substrates, can also alter their magnetic anisotropy. All these concern to both magnetization easy and hard axis directions as well as the magnetization reversal processes [5]. In LSMO thin films deposited on (001) SrTiO3 (STO) substrates can compete three in-plane magnetic anisotropy terms: magnetocrystalline biaxial anisotropy (four-fold symmetry), originating from tensile strain, uniaxial magnetic anisotropy (two-fold symmetry), originating from a preferential substrate step orientation, and shape anisotropy, in the case of patterned nanostructures. The biaxial anisotropy present the easy in-plane direction along [110] and the hard in-plane direction along [100] [4,6,7,8,9,10] where as the easy-axis of the uniaxial anisotropy lies parallel to the substrate step edge direction [11-14]. This uniaxial contribution dominates at room temperature in LSMO (100) films grown on very low miscut STO (100) substrates (0.13º and 0.24º) [11], which vanishes at low temperature where biaxial
magnetocrystalline anisotropy dominates (160 K). It has also been
Data Loading...
