Structural and magnetic properties of a series of low doped   Zn$_{1-x}$Co$_x$O thin films deposited from Zn and Co metal targets on (0001)   Al$_2$O$_3$ substrates
  We report on the synthesis of low doping Zn$_{1-x}$Co$_x$O ($0<x<0.1$) thin films on (0001)-Al$_2$O$_3$ substrates. The films were prepared in an oxidizing atmosphere, using the pulsed laser deposition technique starting from Zn and Co metallic targets. We first studied the influence of the strains of ZnO and their stuctural properties. Second, we have investigated the structural and the magnetic properties of the Zn$_{1-x}$Co$_x$O films. We show that at low doping, the lattice parameters and the magnetization of the Zn$_{1-x}$Co$_x$O films depend strongly on the Co concentration. 
A. Fouchet, W. Prellier, P. Padhan, Ch. Simon, B. Mercey, V.N.   Kulkarni, T. Venkatesan