Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 22: FV intern Symposium: "Heusler Alloys"
Invited Talks Kübler/Yamamoto/Inomata/Silvia Picozzi
MA 22.3: Hauptvortrag
Donnerstag, 29. März 2007, 11:15–11:45, H10
giant tunnel magnetoresistance at room temperature using Co2Fe(SiAl) full Heusler alloy electrodes — •koichiro inomata1,2,3, naomichi ikeda2, and nobuki tezuka2,3 — 1National Institute for Materials Science, Tsukuba, Japan — 2Tohoku University, Sendai , Japan — 3CREST-JST, Saitama, Japan
Half-metallic ferromagnets (HMFs) are a key material for spintronics, which have a band gap at the Fermi level (EF) for one spin direction and thus exhibit 100% spin polarization at the EF. Full Heusler alloys, in particular, are promising as a half metal, because a number of which have been predicted to be HMFs and have a high Curie temperature. Here we report the giant TMR observation at room temperature (RT) for the MTJ using Co2Fe (Si,Al) (CFSA) electrodes. We first investigate the structure of the sputtered CFSA films on a Cr-buffered MgO (001) substrate in an ultrahigh vacuum by post annealing at various temperatures. Next we fabricate the epitaxially grown spin-valve type MTJs on a Cr-buffered MgO (001) substrate with Co2FeSi0.5Al0.5 full-Heusler alloys for top and bottom electrodes and an MgO barrier with different thicknesses. The bottom CFAS film is post-annealed at 673 K after the deposition at RT, followed by the deposition of the other films at RT. The junctions are the annealed at various temperatures, and then microfabricated into 100 mm2 using the electron beam lithography and Ar ion milling. We have successfully grown the highly ordered CFSA full-Heusler films for top and bottom electrodes. As a result we have attained the giant TMR over 200% at RT.