Properties of half-metallic double-perovskite thin films

This paper reports the magnetic, and electrical properties of epitaxial thin films with an ordered double-perovskite structure. High-quality Sr₂FeMoO₆ (SFMO) and Sr₂CrReO₆ (SCRO) films have been grown by sputtering onto the completely lattice-matched substrates of Ba_0.4Sr_0.6TiO₃-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-T_c values (385 K for SFMO and 620 K for SCRO). The atomically flat surfaces free from any surface precipitate enable us to employ a standard photolithographic process for fabricating magnetic tunnel junctions based on these films. Magnetic tunnel junctions are completed with a native barrier formed by surface oxidation of a base-electrode film and a Co counterelectrode, showing 10% tunnel magnetoresistance (TMR) ratio at 4.2 K for a SFMO film.