High-energy ion beam irradiation of Co/NiFe/Co/Cu multilayers: Effects on the structural, transport and magnetic properties

The aim of this work is to investigate the effects of 593 MeV Au irradiation using two different projectile charges, namely Au30+ and Au46.3+ on the structural, transport and magnetization properties of Co/NiFe/Co/Cu multilayers. X-Ray diffraction and extended X-ray absorption fine structures measurements show no significant structural change for as deposited and irradiated multilayers. On the other hand, the magnetoresistance amplitude decreases with the ion fluence but it is insensitive to the projectile charge state. The correlation between changes in the magnetoresistance and remanent magnetization suggests that the main effect responsible for the decrease of the magnetoresistance is the creation of ferromagnetic pinholes. These results are discussed on basis of the electronic thermal spike model and nuclear cascades theory and show similarities to the effects observed at low-energy ion-beam irradiation.