Nanostructured La-Sr-Mn-Co-O Films for Room-Temperature Pulsed Magnetic Field Sensors

The results of Co substitution for Mn in nanostructured La1-xSrxMn1-yCoyO3 films (x = 0.2) grown on polycrystalline Al2O3 substrates by pulsed-injection metal-organic chemical vapor deposition technique, are presented. The Co content y in the films was changed as follows: 0; 0.023; 0.053; 0.078. The resistivity (rho) dependences on temperature in zero magnetic field was investigated in the temperature range 5-300 K. It was found that the increase in Co content up to 0.078 results in the decrease of metal-insulator transition temperature and increase of the resistivity. The results of nanostructured films are compared with the epitaxial films grown on LaAlO3 substrate keeping the same technological conditions. The magnetoresistance (MR) and MR anisotropy (MRA) were investigated at room temperature (290 K) in permanent magnetic fields up to 2.35 T, and pulsed magnetic fields up to 20 T. It was found that the highest MR values are obtained for the intermediate Co content: y = 0.053, while the MRA decreased with the increase of Co content. The results are discussed within the double-exchange interaction model for the perovskite oxides. The possibility to apply the manganite-cobaltite films for the development of room temperature B-scalar magnetic field sensors is considered.