Low switching field of sub-micron sized MTJs with synthetic ferrimagnet free layer based on NiFe/Ru/NiFe multilayers

A synthetic ferrimagnetic multilayer was proposed for the free layer of MTJ. Synthetic ferrimagnet has a single domain structure even at low aspect ratio, thus, the switching field of MTJ can be remained low for the very small sized cell. MTJs with synthetic ferrimagnetic free layer based on NiFe were fabricated to reduce switching field. Stacking structure of Si/SiO₂(10000)/Ta(200)/NiFe(t₁)/CoFe(0∼3)/Ru(4)/CoFe(0∼3)/NiFe(t₂)/Al (20)-O/CoFe(40)/IrMn(100)/Cr(50)/Au(500) were deposited by high vacuum magnetron sputtering. MR curves were measured by using a conductive atomic force microscope. From the MR curves, switching field was defined the width of hysteresis swept 90% of normalized MR as two times of switching field.