Felio A. Perez

Changes in magnetic properties of Co/Pd multilayers induced by hydrogen absorption

The saturation magnetization (MS) and perpendicular anisotropy energy (KP) of Co/Pd multilayers were studied when the samples were exposed to 1 atm of H2 at room temperature. The samples had fixed Co nominal thicknesses of 2.5 A and 4.5 A and Pd thickness values ranging from 0 A to 25 A. The interface structure was determined from the x-ray scattering length density (SLD) profile. When the Pd thickness was less than 10 A, there was a large amount of interface disorder which resulted in no change in MS and KP. As the Pd thickness increased, the SLD contrast between the Co and Pd layers also increased, leading to a decrease in MS and KP after H2 absorption. This can be explained by a decrease in H2 solubility as interface alloying became more dominant for thinner layers, which resulted from a smaller hydrogen electron transfer to the Pd 4d band. The changes in MS and KP in the less interdiffused samples also resulted from this electron transfer. Magnetic changes were reversible with characteristic absorptio...