Magnetoresistive stacks with an unpinned, fixed synthetic anti-ferromagnetic structure and methods of manufacturing thereof

A method of fabricating a fixed magnetic region in a magnetic tunnel junction (MTJ) stack, comprising:

• forming a first layer including a cobalt-iron-boron alloy, wherein the first layer is formed on a seed layer including tantalum;
• forming a second layer including a cobalt-iron-boron alloy;
• forming a coupling layer between the first layer and the second layer;
• and
• forming a third layer including a cobalt-iron alloy between the first layer and the coupling layer,
• wherein the resultant fixed magnetic region consists of a fixed synthetic anti-ferromagnetic (SAF) structure without a pinning layer.

A method of fabricating a magnetic tunnel junction (MTJ) stack, comprising:

• forming a free magnetic region;
• forming a fixed magnetic region consisting of an unpinned, fixed synthetic anti-ferromagnetic (SAF) structure, wherein forming the fixed magnetic region includes:
• forming a first layer including a cobalt-iron-boron alloy, wherein the first layer is formed on a seed layer including tantalum;
• forming a second layer including a cobalt-iron-boron alloy;
• forming a coupling layer between the first layer and the second layer;
• and
• forming a third layer between the first layer and the coupling layer;
• and
• forming an intermediate region between the free magnetic region and the fixed magnetic region.