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Micromagnetic modeling of magnetization reversal mechanisms in Fe based nanostructures

Felipe Garcia-Sanchez (Materials Science Institute of Madrid, ICMM-CSIC, Spain)


Recent advances in lithography opened the possibility to prepare arrays of magnetic nanostructures with the aim to control the magnetisation processes in restricted geometry. With its large saturation magnetization, which induces strong shape anisotropy, and easy availability, Fe constitutes an ideal material for such purposes. Particularly, in this work we study the coercivity mechanisms of lithographed arrays of antidots and stripes. Alternatively, ribbon-shape objects (nanowires) can be created by extrusion technique, although with less control of particle orientations. Micromagnetic modeling allows understanding the magnetic behavior of these systems in relation to experimental measurements. We will model the coercivity mechanism in such structures and compare with experimental results and discuss several possible origins of the differences, such as magnetoelastic effects or surface anisotropy. In nanowires, where the thermal switching is expected to play an important role for small transverse dimensions, we calculate the energy barrier dependence on the nanowire width and the corresponding thermal coercivity value. For this purpose we will introduce a Lagrangian multiplier method for calculating energy barriers in small nanostructures. For antidot arrays we also consider two possible coercivity mechanisms, one comprising the existence of a domain wall originated in the non-lithographed exterior region and the other - originated from the magnetic structures surrounding the antidot border. We compare the calculated angular dependence of coercivity in both models with experimental measurements.