Large low field magnetoresistance in ultrathin nanocrystalline magnetite Fe3O4 films at room temperature

Ultrathin (15 nm) Fe3O4 nanocrystalline films with (111) spinel texture have been prepared by rapid annealing of amorphous ion oxide films. Large low field magnetoresistance (LFMR), with the values of about -6.3% at 300 K and -10% at 200 K under a field of 0.5 T, has been observed in the films. The LFMR is mainly attributed to the boundary tunneling of high spin-polarized electrons in Fe3O4 grains of the films and nearly follows a simple relationship between MR and polarization for intergranular tunneling. The fabricating method here seems to be a good approach to prepare high quality Fe3O4 nanocrystalline films with a large LFMR at room temperature. (C) 2007 American Institute of Physics.