Magnetic tunnel junction with low defect rate after high temperature anneal for magnetic device applications

A magnetic tunnel junction (MTJ) element in a magnetic device, comprising:

• a reference layer that includes a first magnetic layer, a second magnetic layer, a third magnetic layer, a fourth magnetic layer, and a non-magnetic layer, wherein the first magnetic layer has a first concentration of boron and the second magnetic layer has a second concentration of boron that is less than the first concentration, wherein the third magnetic layer is located between one of the first and second magnetic layers and the non-magnetic layer, wherein the fourth magnetic layer is located under the non-magnetic layer, wherein the first, second and third magnetic layers each have a magnetic moment in a first direction, wherein the fourth magnetic layer has a magnetic moment in a second direction opposite the first direction;
• a tunnel barrier layer over the reference layer;
• a free magnetic layer over the tunnel barrier layer that includes a first free magnetic layer having a third concentration of boron and a second free magnetic layer having a fourth concentration of boron that is less than the third concentration, and wherein one or both of the first and second free magnetic layers have a multilayer configuration comprised of one or more layers of boron and one or more layers that include a material selected from Co, Fe, CoFe, CoFeNi, CoFeB, and CoFeQ wherein Q is one of Zr, Hf, Nb, Ta, Mo, and W;
• wherein
• the first magnetic layer contacts a first surface of the tunnel barrier, the first free magnetic layer contacts a second surface of the tunnel barrier layer that is opposite to the first surface;
• and
• a metal oxide capping layer disposed directly on the free magnetic layer.