Changes of interlayer exchange coupling in Fe/Si/Fe trilayer structure by photo-irradiation

The interlayer exchange coupling of the room-temperature-grown Fe/Si/Fe trilayer structure was studied by using spin-polarized secondary-electron microscopy. For the nominal Si spacer thickness in the 0.5-5.0 nm range, the interlayer exchange coupling between the Fe layers measured at room temperature was always ferromagnetic, and had a maximum at the nominal Si spacer thickness of 1.3 nm. By the laser irradiation (λ = 532 nm and the intensity of 28.4 mW/mm2), the interlayer exchange coupling weakened at the spacer thickness below 2.7 nm, while the ferromagnetic coupling between the Fe layers still remained. These phenomena can be qualitatively understood by the assisted tunneling theory with spin-flip processes in the semiconducting spacer layer.