Effect of Fe and Ni ion implantation on the magnetoresistance of La0.7Sr0.3MnO3 thin films

Implantation of 56Fe and 58Ni ions with low and moderate doses is employed to create lattice disorder and point defects in order to study their influence on the magnetoresistance of La0.7Sr0.3MnO3 thin films. Two step ion implantation was carried out to distribute the implanted species across the whole layer thickness. The total dose was divided in the relation 1:2.5 on the energies 120 and 350 keV and varied between 3.5 x 1013 cm-2 and 5 x 1015 cm-2. RBS of He+ ions in random and channeling direction was used to detect the radiation damage. With increasing implantation dose the temperature of maximum magnetoresistance shifts to lower values. The low temperature transition from metallic conductivity to an increase of resistivity with decreasing temperature and the strong scattering of the resistance values in this region observed for medium implantation doses are discussed as due to percolation in an inhomogeneous state of coexisting ferromagnetic metallic and antiferromagnetic insulating clusters. (Abstract Copyright [2003], Wiley Periodicals, Inc.)