How many bits in a single magnetic dot?
Résumé
Digital information processing relies on the handling of two states, called bits or '0' and '1'. In magnetoelectronic devices bits are stored using the two possible directions of magnetization in nanoscale bistable domains. In hard-disk drives these are written in continuous thin films, while in Magnetic Random Access Memories (MRAMs) or for other concepts of magneto-logic devices bits rely on single-domain flat elements patterned with lithography. While miniaturisation is the conventional way to fuel the continuous increase of device density, disruptive solution are also sought. For patterned elements, e.g. disk-shaped, it has been proposed that bits could be stored in dots displaying a flux-closure magnetic state, coded in the chirality of the structure or in the up-or-down magnetic vortex at the center of the dot. In this Letter we go one step further, and show numerically and experimentally that a third bit, i.e. implying in principle eight independent micromagnetic states, could be stored in a simple magnetic dot. This is achieved by considering an elongated dot, in which case the vortex is replaced by a more complex domain wall displaying two internal degrees of freedom.
Domaines
Autre [cond-mat.other]
Origine : Fichiers produits par l'(les) auteur(s)