Olivier Boulle

Affiliations

• SPINTEC, Grenoble, France
• Institut Néel, Grenoble, France
• Elettra Sincrotrone, Trieste, Italy
• LSPM , Université Paris 13, Villetaneuse, France.

Title

Room temperature chiral magnetic skyrmion in ultrathin magnetic nanostructures

Abstract

Magnetic skyrmions are nanometer scale whirling spin configurations that were predicted in the 80’s [1] but were observed only recently. Their small size, topological protection and the fact they can be moved by very small current densities has opened a new paradigm to manipulate magnetization at the nanoscale [2]. This has led to novel concepts of memory and logic devices where skyrmions are the information carriers. A key feature of this spin structure is its chirality, which is at the origin of its topological protection. To date, chiral magnetic skyrmions have been demonstrated only in B20 bulk materials, such as MnSi [3], FexCo1-xSi [4] or FeGe [5], and at the surface of ultrathin magnetic films [6]. However, these observations were carried out in the presence of a large external magnetic field and at low temperature which prevents any application to devices. Furthermore, these materials were deposited using slow epitaxial deposition techniques, while faster sputtering deposition techniques are needed for industrial applications. Here we report on the experimental observation of stable magnetic skyrmions at room temperature without applied magnetic field in a Pt/Co/MgO sputtered ultrathin magnetic nanostructure. We used photoemission electron microscopy combined with X-ray magnetic circular dichroism (XMCD-PEEM) to demonstrate its chiral Néel internal structure. The skyrmions have been observed in sub-micrometer dots or wires and their sizes are typically of the order of 130 nm. Spin wave spectroscopy measurements confirm the presence of a large Dzyaloshinskii Moryia interaction in our thin films (D=2 mJ/m2), which explains the observed chiral order. Our experimental observations are well reproduced by micromagnetic simulations and numerical modelling. This allows the identification of the physical mechanisms governing the size and stability of the skyrmions, which are keys for the design of devices based on the manipulation of skyrmions.

References

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