Tailoring the magnetic properties of Fe asymmetric nanodots

Asymmetric dots as a function of their geometry have been investigated using three-dimensional (3D) object oriented micromagnetic framework (OOMMF) code. The effect of shape asymmetry of the disk on coercivity and remanence is studied. Angular dependence of the remanence and coercivity is also addressed. Asymmetric dots are found to reverse their magnetization by nucleation and propagation of a vortex, when the field is applied parallel to the direction of asymmetry. However, complex reversal modes appear when the angle at which the external field is applied is varied, leading to a non-monotonic behavior of the coercivity and remanence.

Research highlights
► In this work, by means of numerical simulations we have investigated Fe asymmetrical dots as a function of their geometry.
► Coercivity and remanence are strongly influenced by the asymmetry, presenting a non-monotonic behavior.
► According to our results we can conclude that the existence of some degree of asymmetry defines the region of vortex nucleation and its chirality during the reversal of the magnetization.
► Also we have extended our results to the case of an angular dependence of the coercivity and remanence, where a transition form vortex-mode to coherent-mode rotation has been observed.
► The light shed by our results on these phenomena is not only of fundamental interest, but also of importance for the engineering of future high-density data storage systems for which asymmetry can be useful for tailoring specific magnetic characteristics of these systems.