Eur. Phys. J. B 66, 315-319 (2008)
https://doi.org/10.1140/epjb/e2008-00439-7

Structural and magnetic properties of layered Ca₃Co₄O₉ thin films

¹ Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), UMR 7504 ULP-CNRS (ULP-ECPM), BP 43, 23 rue du Loess, 67034 Strasbourg Cedex 2, France
² Institut d'Electronique du Solide et des Systèmes (InESS), UMR 7163 ULP-CNRS, BP 20, 23 rue du Loess, 67037 Strasbourg Cedex 2, France

Corresponding author: ^a colis@ipcms.u-strasbg.fr

Received: 18 July 2008
Revised: 24 October 2008
Published online: 4 December 2008

Abstract

Layered cobalt oxides Ca₃Co₄O₉ thin films have been grown directly on c-cut sapphire substrates using pulsed laser deposition. X-ray diffraction and transmission electron microscopy characterizations show that the deposited films present the expected monoclinic structure and a texture along the direction perpendicular to the Al₂O₃(001) plane. The Ca₃Co₄O₉ structure presents six variants in the film plane. Rutherford backscattering spectroscopy shows that the films are stoichiometric and that the film thickness agrees with the nominal value. The susceptibility χ of the films, recorded along the c-axis of the substrate, after field cooling and zero field cooling in an applied field of 1 kOe shows two magnetic transitions at 19 and 370 K which agree well with previous findings on single crystal samples. In turn, at low temperature (5 K), the magnetization curve along the c-axis exhibits coercive field and remanent magnetization much smaller than those reported for bulk samples, which can be related to the influence of structural variants and structural defects.