Abstract
We have successfully deposited Fe4N thin films with (111) out-of-plane orientation on thermally oxidized Si substrates using a facing-target-sputtering system. A Ta/Ru composite buffer layer was adopted to improve the (111) orientation of the Fe4N thin films. The N2 partial pressure and substrate temperature during sputtering were optimized to promote the formation of the Fe4N phase. Furthermore, we measured the transport spin polarization of (111) oriented Fe4N by the point contact Andreev reflection (PCAR) technique. The spin polarization ratio was determined to be 0.50 using a modified BTK model. The film thickness dependence of the spin polarization was also investigated. The spin polarization of Fe4N measured by PCAR does not show degradation as the sample thickness was reduced to 10nm.
Highlights
Ferromagnetic materials with large spin polarization are of great interest for improving the tunneling/giant magnetoresistance ratio of spintronic devices
The spin polarization of Fe4N has been experimentally confirmed by point contact Andreev reflection (PCAR) on a (100) oriented Fe4N thin film.[2]
Magnetic tunnel junctions (MTJ) with Fe4N ferromagnetic electrodes has been reported and their MR ratios are as large as 75% at room temperature.[3,4]
Summary
Ferromagnetic materials with large spin polarization are of great interest for improving the tunneling/giant magnetoresistance ratio of spintronic devices. The Ta/Ru buffer layer potentially works as the bottom electrodes of the MTJ/GMR3,4 and the nonmagnetic materials in the spin pumping devices.[14] The nitrogen compositions of the films and the deposition temperature were tuned to optimize the phase formation of Fe4N. The thickness dependence of the spin polarization was studied
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