  Pd(100) ultrathin films show ferromagnetism induced by the confinement of
electrons in the film, i.e., the quantum-well mechanism. In this study, we
investigate the effect of the change in the interface structure between a Pd
film and SrTiO3 substrate on quantum-well induced ferromagnetism using the
structural phase transition of SrTiO3. During repeated measurement of
temperature- dependent magnetization of the Pd/SrTiO3 system, cracks were
induced in the Pd overlayer near the interface region by the structural phase
transition of SrTiO3, thereby changing the film-thickness dependence of the
magnetic moment. This is explained by the concept that as the magnetic moment
in Pd(100) changed, so too did the thickness of the quantum-well. In addition,
we observed that the ferromagnetism in the Pd(100) disappeared with the
accumulation of cracks due to the repetition of the temperature cycle through
the phase-transition temperature. This suggests that lowering the crystallinity
of the interface structure by producing a large number of cracks has a negative
effect on quantum-well induced ferromagnetism.
