Influence of Fe3O4 on metal-insulator transition temperature of La0.7Ca0.3MnO3 thin films

In this work, the magnetic and transport properties of La0.7Ca0.3MnO3 (LCMO) films are compared with films capped with Fe3O4. The capping layers for films with the thicknesses of 50 nm and 100 nm broadened the metal-insulator transition, though they produced rather few changes to other properties. The results were dramatically different for a 20-nm-thick LCMO layer compared to other thicker films. The metal-insulator transition temperature increased from 160 to 200 K for capped LCMO film despite the fact that the capping layer reduced the magnitude of magnetization. The temperature of maximum magnetoresistance (MR) shifted from 115 to 185 K. However, its magnitude, 1500% at 5 T, remained unchanged due to capping. This behavior was attributed to atomic inter-diffusion at the LCMO/Fe3O4 interface which resulted in the generation of Mn2+ ions. These results are of great significance and suggest a promising future for both the fundamental research and device applications involving thin films of LCMO.