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-dependen
t 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.
Magnetometry and neutron scattering have been used to study the magnetic properties of pressure graded Co/Pd multilayers. The grading of the multilayer structure was done by varying the deposition pressure during sputtering of the samples. Magnetic d
epth profiling by polarized neutron reflectometry directly shows that for pressure-graded samples, the magnetization changes significantly from one pressure region to the next, while control samples sputtered at uniform pressure exhibit essentially uniform magnetic depth profiles. Complementary magnetometry results suggest that the observed graded magnetic profiles are due in part to a decrease in saturation magnetization for regions deposited at progressively higher pressure. Increased deposition pressure is shown to increase coercivity, and for graded samples, the absence of discrete steps in the hysteresis loops implies exchange coupling among regions deposited at different pressures.
