Use of Half Metallic Heusler Alloys in CoFeB/MgO/Heusler Alloy Tunnel Junctions
Andrew P. Chen, Gen G. Feng, Robert D. Shull
Heusler Alloys Co(sub2)FeSi and Co(sub2)MnSi were deposited on both single crystal MgO (100) and polycrystalline SiO(Sub2) silicon thermal oxide substrates and characterized by x-ray diffraction before and after thermal annealing at various temperatures. Co(Sub2)FeSi and Co(Sub2)MnSi deposited on MgO (100) grow as L2(sub1) or B2 structures but grow as an A2 structure on the SiO(sub2) substrate, Co(Sub2)FeSi and Co(Sub2)MnSi were also deposited in a magnetic tunnel junction (MTJ) stack as the free and reference layers above and below the MgO barrier layer respectively, thereby replacing Co(Sub20)Fe(Sub60)B(Sub20) as those layers in the more common MTJ stack. The tunneling magnetoresistance (TMR) ratio is higher if Co(Sub2)FeSi is the free layer, but lower when Co(Sub2)FeSi is the reference layer.