Phase diagram of magnetic states in nickel submicron disks

Abstract

We present a detailed study of the magnetic states in sub-micron nickel disks in the diameter range of 300–900 nm and thickness of 15–55 nm using magnetic force microscopy and micromagnetic simulations. In this dimensional range, we find three main magnetic states, namely: the single domain state, the vortex state, and the stripe domain state. We identify the crossover dimensions between these magnetic states, demonstrating that the disk thickness is the dominant parameter, which is further supported by the fact that the magnetocrystalline anisotropy of the Ni films is thickness dependant and plays a dominant role at large thicknesses. Experimental results are in a very good agreement with micromagnetic modelling using the out-of-plane effective anisotropy constant. Using in-situ high resolution Magnetic Force Microscopy techniques, we investigate in detail the motion of the vortex core under applied in-plane magnetic field and find that vortex nucleates and annihilates at ∼100 Oe.