Single Magnetic Skyrmions

Field-Dependent Size and Shape of Single Magnetic Skyrmions.
Niklas Romming, André Kubetzka, Christian Hanneken, Kirsten von Bergmann, and Roland Wiesendanger
Phys. Rev. Lett. 114, 177203 (2015)

Spin structure of individual Skyrmion in PdFe/Ir(111). (a) Sketch of the experimental setup of a spin-polarized STM tip probing a magnetic Skyrmion. (b) Topographic constant-current SP-STM image measured with out-of-plane sensitive magnetic tip; each blue circular entity is a Skyrmion (U=+200  mV, I=1  nA, T=2.2  K, B=-1.5  T). (c) Magnetic signal (methods [22]) of two Skyrmions measured with an in-plane magnetization of the tip, m→T, revealing a two-lobe structure (U=+250  mV, I=1  nA, T=4.2  K). (d) Same area as in (c) with inverted magnetic field; due to the preserved rotational sense, the contrast is inverted. (e),(f) Line profiles across a Skyrmion along the rectangles in (c) and (d), respectively, and fits with Eq. (1) [(e) c=(0.90±0.01)  nm, w=(1.18±0.02)  nm; (f) c=(0.91±0.01)  nm, w=(1.17±0.01)  nm] and corresponding calculated out-of-plane magnetization mz. The sketches show spins with atomic distance, colorized according to the SP-STM contrast.