Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 22: FV intern Symposium: "Heusler Alloys"
Invited Talks Kübler/Yamamoto/Inomata/Silvia Picozzi

MA 22.2: Invited Talk

Thursday, March 29, 2007, 10:45–11:15, H10

Highly spin-polarized tunneling in fully epitaxial magnetic tunnel junctions with a Co-based full-Heusler alloy thin film and a MgO barrier — •Masafumi Yamamoto, Takao Marukame, Takayuki Ishikawa, Ken-ichi Matsuda, and Tetsuya Uemura — Division of Electronics for Informatics, Hokkaido University, Sapporo 060-0814, Japan

Co-based full-Heusler alloy (Co₂YZ) thin films are highly preferable ferromagnetic materials in spintronic devices. This is because of the half-metallic ferromagnetic nature theoretically predicted for some of these alloys, and because of their high Curie temperatures, which are well above room temperature (RT). We developed fully epitaxial magnetic tunnel junctions (MTJs) with a Co₂YZ thin film and a MgO tunnel barrier (Refs. 1-3), and showed a relatively high tunnel magnetoresistance ratio of 109% at RT (317% at 4.2 K) for Co₂Cr_0.6Fe_0.4Al/MgO/Co₅₀Fe₅₀ MTJs (Ref. 3). Furthermore, the bias voltage dependence of differential conductance of Co₂MnSi/MgO/Co₅₀Fe₅₀ MTJs for the parallel and antiparallel magnetization configurations suggested the existence of a basic energy gap structure for the minority-spin band of the Co₂MnSi electrode (Ref. 2). These results confirm the promise of epitaxial MTJs as a key device structure for utilizing the potentially high spin polarization of Co₂YZ thin films. 1) T. Marukame et al., Appl. Phys. Lett. 88, 262503 (2006). 2) T. Ishikawa et al., Appl. Phys. Lett. 89, 192505 (2006). 3) T. Marukame et al., to be published in Appl. Phys. Lett.