Enhanced tunneling spin polarization from ultrathin layers of amorphous CoFe

Li Gao; Xin Jiang; Rice, Philip M.; Parkin, Stuart S. P.
September 2009
Applied Physics Letters;9/21/2009, Vol. 95 Issue 12, p122503
Academic Journal
The tunneling spin polarization of CoFe alloys is directly compared in their amorphous (<∼25–30 Å) and crystalline states using superconducting tunneling spectroscopy measurements of Al95Si5/Al2O3/CoFe junctions. Ultrathin layers of normally crystalline CoFe are made amorphous by sandwiching them between amorphous alumina tunnel barriers and amorphous ferromagnetic CoFeB electrodes. The results show that the tunneling spin polarization is significantly enhanced when the CoFe alloy is made amorphous compared to when it is crystalline. We also show that a postdeposition atomic oxygen treatment of the alumina tunnel barrier significantly enhances the thermal stability of the junctions.


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