Magnetoresistive stacks and methods therefor

An magnetoresistive device, comprising:

• an intermediate region;
• a magnetically fixed region on one side of the intermediate region;
• and
• a magnetically free region on an opposite side of the intermediate region, wherein the magnetically free region includes at least a first ferromagnetic region and a second ferromagnetic region separated by a non-magnetic insertion region, wherein at least one of the first ferromagnetic region and the second ferromagnetic region includes at least a boron-rich ferromagnetic layer positioned proximate a boron-free ferromagnetic layer, wherein
• the boron-rich ferromagnetic layer includes one or more of (a) an alloy of iron and boron having a composition FeXB100-X, (b) an alloy of cobalt and boron having a composition CoXB100-X, (c) an alloy of a cobalt-iron alloy and boron having a composition (CoFe)XB100-X, and (d) an alloy of cobalt, iron, and an element M, where element M is one of tantalum, hafnium, zirconium, or chromium, and boron having a composition (CoFeM)XB100-X, and wherein X is between 40 and 80 in atomic percent, and
• the boron-free ferromagnetic layer includes an alloy of iron and cobalt having a composition CoXFe100-X, where X is between 0 and 100 in atomic percent.