Tuning perpendicular anisotropy gradient in Co/Pd multilayers by ion irradiation

The tunability of Ar⁺ ion irradiation of Co/Pd multilayers has been employed to create depthdependent perpendicular anisotropy gradients. By adjusting the Arþ kinetic energy and fluence, the depth and lateral density of the local structural modification are controlled. First-order reversal curve analysis through X-ray magnetic circular dichroism and conventional magnetometry studies shows that the local structural damage weakens the perpendicular anisotropy near the surface, leading to a magnetization tilting towards the in-plane direction. The ion irradiation method is complementary to and may be used in conjunction with, other synthesis approaches to maximize the anisotropy gradient.