Heulser alloys Fe2Cr1 xCoxSi (FCCS) with different Co compositions x have been predicted to
have high spin polarization. High perpendicular magnetic anisotropy (PMA) has been observed in
ultra-thin FCCS films with magnetic anisotropy energy density up to 2.3 106 erg/cm3. The perpendicular
magnetic tunnel junctions (p-MTJs) using FCCS films with different Co compositions x
as the bottom electrode have been fabricated and the post-annealing effects have been investigated
in details. An attractive tunneling magnetoresistance ratio as high as 51.3% is achieved for p-MTJs
using Fe2CrSi (FCS) as the bottom electrode. The thermal stability D can be as high as 70 for
40 nm dimension devices using FCS, which is high enough to endure a retention time of over 10
years. Therefore, Heusler alloy FCS is a promising PMA candidate for p-MTJ application.