The method manufactures high-purity ferromagnetic sputter targets by cryogenic working the sputter target blank at a temperature below at least -50.degree. C. to impart at least about 5 percent strain into the sputter target blank to increase PTF uniformity of the target blank. The sputter target blank is a nonferrous metal selected from the group consisting of cobalt and nickel; and the nonferrous metal has a purity of at least about 99.99 weight percent. Finally, fabricating the sputter target blank forms a sputter target having an improved PTF uniformity arising from the cryogenic working.