Large tunnel magnetoresistance at room temperature with a Co2FeAl full-Heusler alloy electrode

Okamura, S.; Miyazaki, A.; Sugimoto, S.; Tezuka, N.; Inomata, K.
June 2005
Applied Physics Letters;6/6/2005, Vol. 86 Issue 23, p232503
Academic Journal
Magnetic tunnel junctions (MTJs) with a Co2FeAl Heusler alloy electrode are fabricated by the deposition of the film using an ultrahigh vacuum sputtering system followed by photolithography and Ar ion etching. A tunnel magnetoresistance (TMR) of 47% at room temperature (RT) are obtained in a stack of Co2FeAl/Al–Ox/Co75Fe25 magnetic tunnel junction (MTJ) fabricated on a thermally oxidized Si substrate despite the A2 type atomic site disorder for Co2FeAl. There is no increase of TMR in MTJs with the B2 type Co2FeAl, which is prepared by the deposition on a heated substrate. X-ray photoelectron spectroscopy (XPS) depth profiles in Co2FeAl single layer films reveal that Al atoms in Co2FeAl are oxidized preferentially at the surfaces. On the other hand, at the interfaces in Co2FeAl/Al–Ox/Co75Fe25 MTJs, the ferromagnetic layers are hardly oxidized during plasma oxidation for a formation of Al oxide barriers.


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