Thickness-dependent appearance of ferromagnetism in Pd(100) ultrathin films

Abstract

We report the appearance of ferromagnetism in thin films of Pd(100), which depends on film thickness in the range of $3\text{--}5$ nm on ${\mathrm{SrTiO}}_{3}$(100) substrates. X-ray magnetic circular dichroism measurement shows the intrinsic nature of ferromagnetism in Pd(100) films. The spontaneous magnetization in Pd(100) films, corresponding to is $0.61{\ensuremath{\mu}}_{B}$/atom, is comparable to Ni, and it changes in an oscillatory manner depending on film thickness, where the period quantitatively agrees with the theoretical prediction based on the two-dimensional quantum well in the film. This indicates that the discrete electronic states in the quantum well shift to Fermi energy to satisfy the condition for ferromagnetism (Stoner criterion) at a specific film thickness.