PI-MOCVD technology of (La, Sr)(Mn, Co)O3: From epitaxial to nanostructured films

Abstract

The novel La1-xSrx(Mn1-yCoy)zO3 (LSMCO) films were grown by Pulsed-Injection Metalorganic Chemical Vapor Deposition (PI-MOCVD) technique on different oxide substrates. The structural, transport and magnetic properties of the LSMCO films were investigated in terms of crystal structure, texture, electric and magnetoresistive properties of the films for room temperature applications in magnetic sensing. Additionally, to lattice matching-mismatching approach between the film and the substrate, chemical engineering in form of chemical doping was investigated. A certain Co content (from 0 up to 0.17) was introduced into non-stoichiometric La1-xSrx(Mn1-yCoy)zO3 films (z = 1.15) and revealed that Mn non-stoichiometry as well as Co content, influences the changes of transition from metal to insulator state temperature TMI. For epitaxial films (LSMCO grown on LaAlO3) the transition temperature (TMI) was very close to Curie temperature (Tc – transition from ferromagnetic to paramagnetic state), whereas for nanostructured films (LSMCO on Sapphire and ceramic Al2O3), the transition temperatures were lower in comparison to Tc. It was found, that for all used substrates the transition temperature tends to decrease with the increase of Co-content in the films. The change of magnetoresistance properties with Co-content was observed and revealed highest magnetoresistance values at room temperature for the films with Co-content of ~0.06 up to 2.3 T magnetic field, leading to improved and controlled sensing properties at low magnetic fields.