  Depth-grading of magnetic anisotropy in perpendicular magnetic media has been
predicted to reduce the field required to write data without sacrificing
thermal stability. To study this prediction, we have produced Co/Pd multilayers
with depth-dependent Co layer thickness. Polarized neutron reflectometry shows
that the thickness grading results in a corresponding magnetic anisotropy
gradient. Magnetometry reveals that the anisotropy gradient promotes domain
nucleation upon magnetization reversal - a clear experimental demonstration of
the effectiveness of graded anisotropy for reducing write-field.
