Investigating magnetic switching behavior of Permalloy nanocap layers deposited on the spin-coated nanospheres

A monolayer of close-packed nanospheres can be used as a template or a mask to produce interesting magnetic nanostructures. Multi-step spin coating process was used to create the densely packed monolayer of nanospheres. Various parameters, such as, spin speed, spin acceleration, spin duration, nanosphere concentration, volume of the solution deposited on the substrate, the duration of each step, and the interval in between the steps, were adjusted to maximize uniform area of monolayer. After a systematic study, we found that the excess solution between the nanospheres should be removed quickly during the spin-coating process so the spheres move closer each other and form the close-packed monolayer. The spin coated nanospheres were examined using an optical microscope and a scanning electron microscope. Magnetic materials, such as Permalloy or cobalt, were sputter coated on top of monolayer nanospheres. Magnetic switching behavior of these curved magnetic thin films were investigated using an alternating gradient magnetometer, a vibrating sample magnetometer, and through the magneto-optical Kerr effect measurement. Nanocap layer showed a wider magnetic switching and distinctive magnetic anisotropy compared to the flat thin film samples.