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Effect of the change in the interface structure of Pd(100)/SrTiO3 for quantum-well induced ferromagnetism

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.