Abstract
Magnetic skyrmion materials have the great advantage of a robust topological magnetic structure, which makes them stable against the superparamagnetic effect and therefore a candidate for the next-generation of spintronic memory devices. Bulk MnSi, with an ordering temperature of 29.5 K, is a typical skyrmion system with a propagation vector periodicity of ∼18 nm. One crucial prerequisite for any kind of application, however, is the observation and precise control of skyrmions in thin films at room-temperature. Strain in epitaxial MnSi thin films is known to raise the transition temperature to 43 K. Here we show, using magnetometry and x-ray spectroscopy, that the transition temperature can be raised further through proximity coupling to a ferromagnetic layer. Similarly, the external field required to stabilize the helimagnetic phase is lowered. Transmission electron microscopy with element-sensitive detection is used to explore the structural origin of ferromagnetism in these Mn-doped substrates. Our work suggests that an artificial pinning layer, not limited to the MnSi/Si system, may enable room temperature, zero-field skyrmion thin-film systems, thereby opening the door to device applications.
Highlights
Magnetic skyrmions[1] are topologically stable, vortex-like magnetization states that form periodic, six-fold symmetric lattices.[2,3] Since each skyrmion can be seen as an ultra-stable carrier of information, the crystal itself can be regarded as a high-density, non-volatile information matrix, overcoming the limitations set by the superparamagnetic limit.[4]
The broken inversion symmetry of the spin-orbit coupling is the key condition for the appearance of the Dzyaloshinskii-Moriya interaction (DMI), which is the essential ingredient for the existence of skyrmions
We find ferromagnetism in the seed layer, which persists up to room temperature, and which results in proximity coupling with the MnSi layer above
Summary
Increasing the magnetic ordering temperature and decreasing the skyrmion-stabilizing magnetic field is very important for the future applications of these materials. The skyrmion phase has to be stabilized in zero applied field. These issues remain challenging as there are no reported B20-type helimagnetic materials with a TC above room temperature, and an external field is always required to manipulate the helimagnetism and stabilize the skyrmion phase.[2] Utilizing coupling mechanisms in artificial magnetic heterostructures provides a flexible playground for engineering B20 systems, as well as manipulating their helimagnetism. We find ferromagnetism in the seed layer, which persists up to room temperature, and which results in proximity coupling with the MnSi layer above
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
