Nanomagnetism of cobalt ferrite-based spin filters probed by spin-polarized tunneling

The magnetism of ferrite ultrathin films has been probed at nanoscale by spin-polarized tunneling transport in CoFe2O4-based room-temperature spin filters. By significantly reducing the Pt/CoFe2O4/Al2O3/Co junctions' size (cross sections ∼5 nm) in comparison with usual microjunctions, transport through a ferrite single magnetic domain has been achieved. Our tunnel magnetoresistance measurements at the nanoscale have revealed very well defined resistance states and the generation of the highest spin filtering efficiency (−8%) at room temperature. A uniaxial magnetic anisotropy has been evidenced in CoFe2O4, showing that these magnetotransport measurements offer a unique probe of a single magnetic domain in ferrite ultrathin films.