A magnetoresistive stack comprising: a fixed region having a fixed magnetic state; a spacer region ; a first dielectric layer and a second dielectric layer , where both the first dielectric layer and the second dielectric layer are between the fixed region and the spacer region ; and a free region between the first dielectric layer and the second dielectric layer , the free region configured to have a first magnetic state and a second magnetic state, and the free region being characterized in that it comprises: an insertion layer comprising molybdenum, tungsten, tantalum, or a combination thereof; a first ferromagnetic layer above the insertion layer, the first ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof; and a second ferromagnetic layer above the first ferromagnetic layer , the second ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof, wherein the free region further comprises a transition layer above the second ferromagnetic layer , the transition layer comprising iron, and one or more of the first ferromagnetic layer , the second ferromagnetic layer , or the transition layer comprise 1 atomic percent to 15 atomic percent of auxiliary additional metal, where the auxiliary additional metal includes one or more metals from a group consisting of: chromium, vanadium, manganese, niobium, tantalum, tungsten, gold, copper, silver, rhodium, and palladium. a fixed region having a fixed magnetic state; a spacer region ; a first dielectric layer and a second dielectric layer , where both the first dielectric layer and the second dielectric layer are between the fixed region and the spacer region ; and a free region between the first dielectric layer and the second dielectric layer , the free region configured to have a first magnetic state and a second magnetic state, and the free region being characterized in that it comprises: an insertion layer comprising molybdenum, tungsten, tantalum, or a combination thereof; a first ferromagnetic layer above the insertion layer, the first ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof; and a second ferromagnetic layer above the first ferromagnetic layer , the second ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof, wherein the free region further comprises a transition layer above the second ferromagnetic layer , the transition layer comprising iron, and one or more of the first ferromagnetic layer , the second ferromagnetic layer , or the transition layer comprise 1 atomic percent to 15 atomic percent of auxiliary additional metal, where the auxiliary additional metal includes one or more metals from a group consisting of: chromium, vanadium, manganese, niobium, tantalum, tungsten, gold, copper, silver, rhodium, and palladium. an insertion layer comprising molybdenum, tungsten, tantalum, or a combination thereof; a first ferromagnetic layer above the insertion layer, the first ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof; and a second ferromagnetic layer above the first ferromagnetic layer , the second ferromagnetic layer comprising cobalt, iron, boron, or a combination thereof, wherein the free region further comprises a transition layer above the second ferromagnetic layer , the transition layer comprising iron, and one or more of the first ferromagnetic layer , the second ferromagnetic layer , or the transition layer comprise 1 atomic percent to 15 atomic percent of auxiliary additional metal, where the auxiliary additional metal includes one or more metals from a group consisting of: chromium, vanadium, manganese, niobium, tantalum, tungsten, gold, copper, silver, rhodium, and palladium. <EOS>