The Effect of Size Distribution on the Switching Field Distribution of Co/Pd Multilayered Nanostructure Arrays

We use Ion Beam Proximity Lithography (IBPL) to produce 4 mm times 4 mm arrays of 220 nm dots in perpendicularly - oriented Co/Pd multilayered media. IBPL is used to reduce the size distribution sigma_D of the arrays, and subsequently He⁺ ion irradiation is used to reduce their anisotropy. The switching field distribution sigma_Hcr/H_Cr is measured for each sample before and after irradiation, and a linear relationship is experimentally found between sigma_Hcr/H_Cr and sigma_D. We argue that the slope of the line is due to the self-demagnetization effect of individual dots (and therefore, it is not strictly a line) and that the intercept of the line is inversely proportional to the permeability of the nanostructured material.