Tailoring metallic ferromagnet heterostructures for non-collinear spin states and skyrmions*

Magnetic skyrmions are particle-like knots in the magnetization. They are envisioned as the basis for future spintronic devices and can be stabilized by a favorable interplay of magnetic exchange, Dzyaloshinskii-Moriya interaction (DMI), anisotropy and Zeeman energy. The Fe/Ir(111) interface is known to exhibit strong DMI [1] and serves as an ideal basis to build up materials that host single skyrmions on the nanometer length scale. Such small magnetic objects can be imaged, characterized and manipulated using (spin-resolved) scanning tunneling microscopy (STM) [2].
Building upon the Fe/Ir(111)-interface a fine-tuning of the relevant magnetic energies is performed by adding metallic overlayers, by adorption of hydrogen, or by a variation of the strain within the magnetic film. Magnetic field dependent STM measurements can be used to obtain the specific material parameters [3]. In addition, spectroscopy using a non-magnetic tip electrode reveales the correlation between the local magnetoresistance and the non-collinearity of the spin texture [4]. Such a read-out of the local magnetic state could be combined with the demonstated reversible switching between skyrmion and ferromagnet by local electric fields [5].
[1] Nature Phys. 7, 718 (2011).
[2] J. Phys.: Condens. Matter 26, 394002 (2014).
[3] Phys. Rev. Lett. 114, 177203 (2015).
[4] Nature Nanotech. 10, 1039 (2015).
[5] Nature Nanotech. 12, 123 (2017).