the alumina tunnel barrier layer by plasma oxidation for approximately 120 seconds in the presence of 0 1 torr of oxygen the aluminum layer can also be oxidized by placing this layer in either air or pure oxygen or either air or oxygen with a small amount of water present for optimum magnetoresistance the aluminum layer must be completely oxidized without oxidizing the underlying ferromagnetic electrode the alumina layer can also be formed by reactive dc magnetron sputtering from a metallic aluminum target in a sputtering gas comprised of argon and oxygen with a predominance of argon the amount of oxygen is chosen for optimal growth of the alumina layer without poisoning of the al target a wide variety of antiferromagnetic materials have been studied and reported in the literature as exchange bias materials for mtj applications for which the current flows perpendicularly through the device and for which the thickness of the ferromagnetic pinned layer is very thin the antiferromagnetic material must be metallic the metallic antiferromagnetic materials which are structurally disordered typically display exchange bias over a wide range of composition of the antiferromagnetic metal may be less sensitive to contaminants display exchange bias even for very thin layers at room temperature typically as thin as u02dc 4 5 nm generally display exchange bias after deposition even at room temperature and require only heating above the blocking temperature of the antiferromagnetic to maximize the exchange bias typical examples of this type of metallic antiferromagnetic include fe 1 x mn x mn 1 x co x mn 1 x rh x mn.