Temperature dependent magnetization reversal of exchange biased magnetic vortices in IrMn/Fe microcaps

Abstract

We have investigated the magnetization reversal of vortex structures in Fe as well as in IrMn/Fe magnetic caps at elevated temperatures up to 450 K. The caps were formed by film deposition onto dense arrays of self-assembled silica particles of 900 nm diameter. In the investigated temperature range, the magnetization reversal in Fe caps evolves via nucleation and annihilation of magnetic vortices. However, in exchange coupled IrMn/Fe caps, the magnetic vortex at zero magnetic field vanishes as the temperature approaches the blocking temperature of IrMn accompanied by an increase in coercivity. Further increase in temperature, approaching the Néel temperature of IrMn, results in a reduction of coercivity as well as remanence indicating the re-stabilization of a vortex state.

A new reversal mode in exchange coupled antiferromagnetic/ferromagnetic disks: distorted viscous vortex

“…55 Interestingly, although the thickness of the FM layers in AF/FM dots is typically on the 10 nm scale, some hints of reversal asymmetries probably linked to this new reversal mode can be found in the literature. Originating from the drag of the AF and accompanied by a distortion of the vortex structure rather than a tilt (as shown by simulations), this magnetization reversal mechanism may be viewed as distorted viscous vortex reversal.…”

“…Even in nanostructures with thick AFs, distorted viscous vortex reversal may still emerge if the temperature is sufficiently increased so that the AF anisotropy is concomitantly weakened. 55 Interestingly, although the thickness of the FM layers in AF/FM dots is typically on the 10 nm scale, some hints of reversal asymmetries probably linked to this new reversal mode can be found in the literature. 4,30,55,56 Note that the viscous drag of the magnetization due to the AF also occurs in thin films.…”

“…55 Interestingly, although the thickness of the FM layers in AF/FM dots is typically on the 10 nm scale, some hints of reversal asymmetries probably linked to this new reversal mode can be found in the literature. 4,30,55,56 Note that the viscous drag of the magnetization due to the AF also occurs in thin films. However, in contrast to what is observed in nanostructures, in thin films the net effect of this viscous drag is merely an increase in coercivity without any changes in the magnetization reversal modes.…”

Magnetic coupling of vortices in a two-dimensional lattice

“…This approach is based on selfassembly of spherical silica particles [45] with a diameter of 330 nm followed by deposition of a magnetic permalloy (Py: Ni 81 Fe 19 ) thin film onto the particle array forming Py cap structures [40][41][42][43]. Here we focus on the influence of magnetic coupling on the magnetic properties induced by varying the Py film thickness between 20 and 130 nm.…”

“…In this study, a two dimensional vortex lattice was prepared by magnetic film deposition onto self-assembled densely packed particle arrays forming magnetic cap structures [25,[39][40][41][42][43][44]. Strong coupling is induced by deposition of thick Py films, where neighboring caps will be interconnected at the contact areas, resulting in direct magnetic exchange coupling.…”