US Patent 7502211 MTJ device with partially milled anti-parallel coupled bottom free layer

In a magnetic tunnel junction (MTJ) device having a pinned layer and upper and lower antiparallel-coupled free sublayers, to avoid loss in tunnel magnetoresistance, etching or milling of the free sublayer layer materials is stopped in the lower free sublayer. The total thickness of the free sublayers may be large to ease manufacture because the effective magnetic thickness of the free layer combination may be as small as desired by appropriately establishing a small difference between the thicknesses of the AP-coupled free sublayers. A contiguous hard bias material is centered on the free sublayers for stabilization.