Résumé
NV centers are defects in diamond which can be used as quantum sensors to probe magnetism at the nanoscale when integrated in an atomic force microscope. Such a measurement relies on the spin S = 1 of the NV center: the static stray field produced by a magnetic state induces a Zeeman shift on the spin sublevels, which can be detected optically. The high magnetic sensitivity of this technique allows the imaging of complex antiferromagnetic states, in BiFeO3 for example [1].In addition, NV centers are also sensitive to spin waves, as the magnetic noise originating from thermally activated spin waves accelerates its spin relaxation. In this case, the enhanced relaxation leads to a decrease of the photoluminescence emitted by the NV center [2], which allows an easy localization of spin waves interacting with magnetic textures. We applied this approach to the study of Co-based perfectly compensated synthetic antiferromagnetic layers [3], in which we were able to observe spin waves channeled inside the domain walls [4].We report here on a more detailed investigation of domain walls and skyrmions in synthetic antiferromagnetic layers, revealing that the spatial distribution of the noise and its amplitude are related to the chirality of the magnetic texture. In particular for skyrmions, the magnetic noise contrast around their boundary is linked to their internal structure. [1] A. Finco et al, Physical Review Letters 128, 187201 (2022). [2] M. Rollo et al, Physical Review B 103, 235418 (2021). [3] W. Legrand et al, Nature Materials 19, 34–42 (2020). [4] A. Finco et al, Nature Communications 12, 767 (2021).