  We investigate the response of palladium-cobalt bi-layer thin films to
hydrogen charging at atmospheric pressure for spintronic applications. We find
that hydrogen absorption by the palladium layer results in the narrowing and
shifting of the ferromagnetic resonance line for the material. We explain the
observed phenomena as originating from reduction in spin pumping effect and
from variation in the magnetic anisotropy of the cobalt film through an
interface effect. The shift of the resonance frequency or field is the easiest
to detect. We utilize it to demonstrate functionality of the bi-layer films as
a hydrogen sensor.

Materials Science