The magnetization of Cl-2/Ar etched magnetic multi layer (NiFeCo/CoFe/Cu/CoFe/NiFeCo) structures used in magnetoresistive random access memory elements was measured over a period of similar to 6 months. Very stable magnetic properties were achieved, with no evidence of corrosion, provided chlorinated etch residues were removed by postetch cleaning. including deionized water rinsing or in situ exposure to H-2, O-2 or SF6 plasmas were investigated. Some slight degradation in magnetization was observed in O-2 plasma treated structures, but the other cleaning procedures produced no change in magnetic properties and excellent long-term stability.