Properties of magnetic nanodots with perpendicular anisotropy

TL;DR

This paper investigates how adding perpendicular anisotropy affects the magnetic vortex properties in nanodots, combining simulations, analytical models, and experimental measurements to inform device design.

Contribution

It provides a comprehensive analysis of vortex core behavior under perpendicular anisotropy, including phase diagrams and experimental validation.

Findings

Vortex core radii increase with perpendicular anisotropy.

Phase diagrams are significantly modified by anisotropy.

Experimental MFM measurements confirm simulation trends.

Abstract

Nanodots with magnetic vortices have many potential applications, such as magnetic memories (VRAMs) and spin transfer nano-oscillators (STNOs). Adding a perpendicular anisotropy term to the magnetic energy of the nanodot it becomes possible to tune the vortex core properties. This can be obtained, e.g., in Co nanodots by varying the thickness of the Co layer in a Co/Pt stack. Here we discuss the spin configuration of circular and elliptical nanodots for different perpendicular anisotropies; we show for nanodisks that micromagnetic simulations and analytical results agree. Increasing the perpendicular anisotropy, the vortex core radii increase, the phase diagrams are modified and new configurations appear; the knowledge of these phase diagrams is relevant for the choice of optimum nanodot dimensions for applications. MFM measurements on Co/Pt multilayers confirm the trend of the vortex core diameters with varying Co layer thicknesses.