Methods of manufacturing magnetoresistive mtj stacks having an unpinned, fixed synthetic anti-ferromagnetic structure

A magnetoresistive magnetic tunnel junction (MTJ) stack comprising:

• a free magnetic region having a circular shape;
• an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein the unpinned, fixed SAF structure comprises:
• a first layer of one or more ferromagnetic materials, wherein the one or more ferromagnetic materials of the first layer includes cobalt, iron and boron,
• a second layer of one or more ferromagnetic materials wherein the one or more ferromagnetic materials of the second layer includes cobalt,
• a third layer of one or more ferromagnetic materials wherein the one or more ferromagnetic materials of the third layer includes cobalt, and
• an anti-ferromagnetic coupling layer, wherein:
• the anti-ferromagnetic coupling layer is disposed between the first and second layers, and
• the third layer is disposed between the second layer and the anti-ferromagnetic coupling layer;
• and
• a dielectric layer disposed (i) between the free magnetic region and the fixed magnetic region and (ii) on the first layer of one or more ferromagnetic materials.

A magnetoresistive magnetic tunnel junction (MTJ) stack comprising:

• a free magnetic region having at least one layer of one or more ferromagnetic materials;
• a fixed magnetic region consisting essentially of an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein the unpinned, fixed SAF structure comprises:
• a first layer of one or more ferromagnetic materials, wherein the one or more ferromagnetic materials includes cobalt,
• a multi-layer region including a plurality of layers of ferromagnetic materials, wherein the plurality of layers of ferromagnetic materials include a layer of one or more ferromagnetic materials including cobalt,
• an anti-ferromagnetic coupling layer disposed between the first layer of one or more ferromagnetic materials and the multi-layer region;
• and
• a dielectric layer disposed (i) between the free magnetic region and the fixed magnetic region and (ii) on the first layer of one or more ferromagnetic materials.