Magnetic and junction properties of half-metallic double-perovskite thin films

This paper reports the magnetic, electrical, and microstructural properties of epitaxial thin films with an ordered double-perovskite structure. Sr₂ FeMoO₆ (SFMO) and Sr₂ CrReO₆ (SCRO) films have been grown by sputtering onto the lattice-matched substrates of Ba_0.4 Sr_0.6 TiO₃ -buffered and bare SrTiO₃, respectively. These films exhibit high saturation magnetization M_s values (3.8 μ_B/f.u. for SFMO and 0.9 μ_B/f.u. for SCRO), which are close to the expected values for their half-metallicity, and high curie temperature T_c values (385 K for SFMO and 620 K for SCRO). Surface analyzes by AFM and XPS indicate that these films have atomically flat and well-defined surfaces, which are free from any surface precipitates. This enables us to employ a standard photolithographic process for fabricating magnetic tunnel junctions based on these films. SFMO junctions with a native barrier formed by surface oxidation of a SFMO base-electrode and a Co counterelectrode have shown a tunnel magnetoresistance ratio of 10% at 4.2 K.