Mechanism of grain-boundary magnetoresistance in Fe3O4 films
Department of Superconductivity and Magnetism, University of
Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
Corresponding author: a email@example.com
Published online: 13 August 2002
The magnetotransport properties of magnetite films with different microstructures were investigated in order to identify prerequisites for the attainment of a large tunnelling magnetoresistance in polycrystalline samples. Epitaxial films on MgAl2O4, polycrystalline films on Al2O3 and rough MgAl2O4 substrates and a polycrystalline La0.7Ca0.3MnO3 film on MgO were compared. Although grain boundaries induce a large high-field magnetoresistance in magnetite films, the low-field magnetoresistance characteristic for spin-polarized tunnelling was virtually absent in these samples. Two factors might be responsible for this behaviour: (1) grain boundaries in magnetite are conducting and do not form tunnelling barriers and (2) the spin-polarization near grain boundaries is suppressed due to non-stoichiometry.
PACS: 72.25.-b – Spin polarized transport / 73.50.Jt – Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects) / 75.70.-i – Magnetic properties of thin films, surfaces, and interfaces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002