Orientation and thickness dependence of magnetization at the interfaces of highly spin-polarized manganite thin films

Abstract

APS/??? Orientation and thickness dependence of magnetization at the interfaces of highly spin polarized manganite thin films Rajesh V. Chopdekar, 1, 2, ∗ Elke Arenholz, 3 and Yuri Suzuki 2 School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (Dated: January 14, 2009) Abstract We have probed the nature of magnetism at the surface of (001), (110) and (111)-oriented La 0.7 Sr 0.3 MnO 3 thin films. The spin polarization of La 0.7 Sr 0.3 MnO 3 thin films is not intrinsically suppressed at all surfaces and interfaces but is highly sensitive to both the epitaxial strain state as well as the substrate orientation. Through the use of soft x-ray spectroscopy, the magnetic properties of (001), (110) and (111)-oriented La 0.7 Sr 0.3 MnO 3 /SrTiO 3 interfaces have been inves- tigated and compared to bulk magnetometry and resistivity measurements. The magnetization of (110) and (111)-oriented La 0.7 Sr 0.3 MnO 3 /SrTiO 3 interfaces are more bulk-like as a function of thickness whereas the magnetization at the (001)-oriented La 0.7 Sr 0.3 MnO 3 /SrTiO 3 interface is sup- pressed significantly below a layer thickness of 20 nm. Such findings are correlated with the biaxial strain state of the La 0.7 Sr 0.3 MnO 3 films; for a given film thickness it is the tetragonal distortion of (001) La 0.7 Sr 0.3 MnO 3 that severely impacts the magnetization, whereas the trigonal distortion for (111)-oriented films and monoclinic distortion for (110)-oriented films have less of an impact. These observations provide evidence that surface magnetization and thus spin polarization depends strongly on the crystal surface orientation as well as epitaxial strain. PACS numbers: 73.50.Jt, 75.47.Gk, 75.70.-i