Evolution of the Complexity of Magnetic Domain Structure in Nano-Scale Nickel Particles

The micromagnetic structure of nanofabricated nickel particles has been determined as a function of particle diameter and thickness using a combination of high-resolution magnetic force microscopy and LandauLifshitz-Gilbert micromagnetic simulations. Cylindrical particles were lithographically prepared with diameters in the range 68 900 nm, and thickness between 48 and 140 nm. Extensive measurements and simulations of the 100 nm thick cylinders are reported in this note. At this thickness, the complexity of observed magnetic states increases as the particle diameter increases. Single domain structures are found at the smallest diameters, with twoand three-domain structures appearing at larger diameters, characterized by in-plane vorticity and in the simplest case, a vortex ring. At diameters greater than at least 360 nm, the magnetic structure is composed of random stripe domains very similar to those found in nickel films of the same thickness.