221 research outputs found
Properties of magnetic nanodots with perpendicular anisotropy
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.Comment: 7 pages, 8 figure
Scaling relations for magnetic nanoparticles
A detailed investigation of the scaling relations recently proposed by [J.
d'Albuquerque e Castro, D. Altbir, J. C. Retamal, and P. Vargas, Phys. Rev.
Lett. 88, 237202 (2002)] to study the magnetic properties of nanoparticles is
presented. Analytical expressions for the total energy of three characteristic
internal configurations of the particles are obtained, in terms of which the
behavior of the magnetic phase diagram for those particles upon scaling of the
exchange interaction is discussed. The exponent in scaling relations is
shown to be dependent on the geometry of the vortex core, and results for
specific cases are presented.Comment: 6 pages, 4 figure
Vortex core size in interacting cylindrical nanodot arrays
The effect of dipolar interactions among cylindrical nanodots, with a
vortex-core magnetic configuration, is analyzed by means of analytical
calculations. The cylinders are placed in a N x N square array in two
configurations - core oriented parallel to each other and with antiparallel
alignment between nearest neighbors. Results comprise the variation in the core
radius with the number of interacting dots, the distance between them and dot
height. The dipolar interdot coupling leads to a decrease (increase) of the
core radius for parallel (antiparallel) arrays
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