Role of Metal-Oxide Interface in Determining the Spin Polarization of Magnetic Tunnel Junctions

• Published in: Science (American Association for the Advancement of Science) Vol. 286; no. 5439; pp. 507 - 509
• Main Authors: de Teresa, Jose Maria, Barthélémy, Agnès, Fert, Albert, Contour, Jean Pierre, Montaigne, François, Seneor, Pierre
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 15.10.1999; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Applied sciences; Climate; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electric potential; Electrodes; Electron paramagnetic resonance; Electron tunneling; Electronic structure; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in interface structures; Electronics; Electrons; Exact sciences and technology; Ferromagnetism; Interfaces; Junction breakdown and tunneling devices (including resonance tunneling devices); Magnetic fields; Magnetism; Magnetization; Mesas; Metal oxides; Metallic oxides; Metals; Nuclear polarization; Physics; Polarization (Nuclear physics); Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Tunnel junctions; Tunneling; Tunnels; Lanthanum oxides; Ternary compounds; Tunnel effect; Spin polarization; Binary compounds; Experimental study; Cobalt; Interface structure; Strontium oxides; Manganese oxides; Electronic structure; Strontium titanates; Tunnel junction; Quaternary compounds; Cerium oxides; Aluminium oxides
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.286.5439.507

The role of the metal-oxide interface in determining the spin polarization of electrons tunneling from or into ferromagnetic transition metals in magnetic tunnel junctions is reported. The spin polarization of cobalt in tunnel junctions with an alumina barrier is positive, but it is negative when the barrier is strontium titanate or cerium lanthanite. The results are ascribed to bonding effects at the transition metal-barrier interface. The influence of the electronic structure of metal-oxide interfaces on the spin polarization raises interesting fundamental problems and opens new ways to optimize the magnetoresistance of tunnel junctions.