Enhanced magnetoresistance behaviour in CeO buffered 2 LaCaMnO films on Si

We have investigated the colossal magnetoresistance behaviour of the La0.70Ca0.30MnO3ydrCeO2rSi 100. structure deposited by pulsed laser deposition. A colossal magnetoresistance, with a Drrr0 ratio of 96% at 97 K in a magnetic field of 12 T, has been obtained in such film structures. A thermally activated resistance behaviour, which follows Mott’s law, i.e., ln R.;Ty1r4 , is observed at temperatures up to the ferromagnetic transition temperature Tc., indicating the possible occurrence of variable range hopping. The dependence of the electrical and the magnetic properties on post-annealing has also been briefly investigated. Enhanced magnetoresistance and maximum-resistivity peak shift to lower temperature can be explained by the weakened ferromagnetic coupling between Mn ions produced by an increase in the Mn–O bond length due to decreased tensile stress, compared with the La0.70Ca0.30MnO3yd films deposited on Si substrate directly. q1999 Elsevier Science B.V. All rights reserved.