  We demonstrate control of the magnetism of Pd(100) ultrathin films, which
show d-electron quantum-well induced ferromagnetism, via modulation of the
interface electronic state using density functional calculation. From an
analysis based on the phase model, forming the Au/Pd(100) interface induces
hybridization of the wave function of d-electron quantum-well states, and
modulates the term of the scattering phase shift as a function of the
reciprocal lattice point. In contrast, forming the Al interface, which has only
s-electrons at the Fermi energy, cannot modify the scattering phase shift. Our
finding indicates the possibility of modifying the phase shift by tailoring the
interface electronic states using hybridization of the wave function, and this
efficiently changes the density of states near the Fermi energy of Pd films,
and the switching between paramagnetism and ferromagnetism occurs based on the
condition for ferromagnetism (Stoner criterion).
