Hard/graded exchange spring composite media based on FePt

Hard-FePt(L1(0))/graded-FePt(L1(0) to A1) exchange spring composite media with perpendicular magnetic anisotropy have been studied. Changing the deposition temperature affects the structural transformation of FePt from cubic phase A1, which is magnetically soft, to the tetragonal phase L1(0), which is magnetically hard. Using this mechanism we were able to fabricate hard/graded composite films. Magnetic measurements revealed a significant reduction of the composite films' switching fields in comparison with those of the single hard layer. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556773]