EFFECT OF ~(56)Fe ION IMPLANTATION ON MAGNETORESISTANCE OF La_(0.7)Sr_(0.3)MnO_3 THIN FILMS

摘要

Thin La_(0.7)Sr_(0.3)MnO_3 films were deposited by magnetron sputtering on a SrTiO_3 (100) substrate. The low and moderate ~(56)Fe ion implantation is employed to create point defects and lattice disorder as well as doping by Fe in order to study their influence on magnetoresistance and for tuning of the properties of LSMO thin film. Ion implantation of Fe~+ was carried out as a two step process. The total dose was divided in the relation 1:2.5 on the energies 120 and 350 keV in order to distribute the implanted species and the radiation damage across the whole layer thickness. The total dose was varied between 3.5 x 10~(13) cm~(-2) and 5 x 10~(15) 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 the magnetoresistance maximum shifts to lower temperatures. This shift is correlated with a remarkable broadening of the maximum in MR(5T). For the LSMO thin films investigated here the optimum implantation dose should be ～10~(14) Fe/cm~2. The strong scattering of the resistivity values at low temperature observed for the medium implantation doses is discussed in the frame of phase separation model.