Angular Dependence of Coercivity on Hemispherical Nanocaps Arrays of Permalloy: An Experimental Analysis and Micromagnetic Simulation

We present experimental and numerical results on the magnetic properties of arrays composed of hemispherical nanocaps of Py. Samples of 5, 10, and 20 nm thickness were obtained by magnetron sputtering deposition on hexagonal arrays of silica nanospheres (SNs). The structural analyses confirmed the existence of Py on the top surface of SN arrangements. The nanocaps are ferromagnetic and the shape of hysteresis loops varies with the thickness, indicating the existence of an easy magnetization axis in the direction parallel to the array plane. The angular dependence of coercivity showed a maximum value at about 70°, relative to the array plane. This behavior is associated with one easy magnetization axis, originating from the dipolar energy along the array and another axis due to the dipolar effects of individual nanocaps. The results are in agreement with those obtained by micromagnetic simulations.