Study of physical properties of magnetic skyrmions for sensing applications

Published : 26 March 2019

Skyrmions are chiral magnetic bubbles: magnetization follows a cycloid along a line across the skyrmion. They can appear in heavy metal/ferromagnet/oxide ultrathin trilayers. Such texture results from the presence of an interfacial interaction called Dzyaloskinskii-Moriya interaction. It makes the skyrmions stable, less sensitive to defects as compared to usual domain walls and easily moveable by electrical current. They are currently very popular as they could be used as dense storage nanoscale data bits, or for magnetic logic.

Their size may be modified by a magnetic field. Moreover, using magneto-optical microscopy, we have recently shown that a gate voltage can modulate the size and density of magnetic skyrmions in ultrathin films, ultimately leading to the realization of a skyrmion switch [1]. This new degree of freedom may thus allow to create multifunctional spintronic devices or to better control the skyrmion properties.

In order to develop skyrmion based spintronic devices, the objectives of this thesis would be:

-to better understand and control the different contributions in the Dzyaloshinskii-Moriya interaction by playing on the materials thanks to a support from theoreticians at Spintec.

– to optimize the tunability of skyrmion properties with the gate voltage by performing a material study. Skyrmion behavior with temperature will also be studied as a device should operate in the -40 to 100°C range for applications.

-to characterize the electrical signature of skyrmions by using magneto-optical microscopy coupled with magnetotransport. This electrical signal is necessary to read the state of a skyrmion-based device but is still a technological challenge, the signals being usually quite small.

– finally, to assess the potential for skyrmions to be used in spintronic devices.

[1] M. Schott et al. Nano Lett., 17, 3006 (2017)

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