Extraordinary tunnel magnetoresistance in half metallic ferromagnetic devices

Magnetic tunnel junctions (MTJ) with large tunnelling magnetoresistance are described. The MTJs are comprised of a half-metallic ferromagnetic Co/sub 2/MnSi (a Heusler alloy) layer, AlO/sub x/ as the insulating tunnel barrier, and a ferromagnetic layer of CoFe. The CoFe layer is pinned by exchange coupling to antiferromagnetic IrMn capped with 60 nm of Ru to prevent oxidation of the antiferromagnetic layer. The Heusler alloy with well defined smooth surface roughness was deposited by sputtering on to oxidized silicon substrates using a seed layer of Ta.