3D magnetic field experiment at BESSY II takes spintronics a step further
This real-space ptychographic phase image of magnetic textures measured at an external magnetic field perpendicular to the sample. It shows a stripe pattern and skyrmions (in the very top part of the sample). © HZB
Micromagnetic simulations show how a small magnetic field in plane with the magnetic stripes can change the magnetic texture from a stripe pattern to a fan pattern.
© HZB
(Fe0.63Ni0.3Pd0.07)3P or FNPP is a magnetic material that exhibits complex magnetic structures even at room temperature. This makes the material of interest for spintronics, a field that could enable data processing with significantly lower energy consumption. One potential application is novel magnetic memory devices. However, generating and modifying the desired structures in a controlled manner remains a challenge to date. A new study led by HZB has now taken a step forward in this regard. They demonstrated at the worldwide unique VEKMAG-Station at BESSY II, that a tiny external B-field in the plane of the magnetic patterns is sufficient to change them.
The team led by Dr Florin Radu investigated FNPP samples using soft X-rays and ptychography at BESSY II. The experiments aimed to map the magnetic textures whilst the sample was exposed to an external magnetic field in specific spatial directions. For this purpose, BESSY II is equipped with a globally unique instrument developed by Radu’s team themselves: the VEKMAG vector magnet can generate a magnetic field of up to 1 T in all three spatial directions.
“We observed that the magnetic stripe domains can be controlled by an external magnetic field when applied parallel to these patterns, rather than perpendicular” says Dr Victor Ukleev, first author of the study. “The surprising thing was that even a very small field of just 10 millitesla was sufficient to transform a chiral stripe configuration into an achiral fan configuration.”
Modelling provides a good explanation for this behaviour. Within the FNPP, different magnetic interactions compete with one another, resulting in complex magnetic textures. While one of these interactions is rather isotropic, another key interaction is anisotropic, with a direction of preference. "Due to our experimental observations, and thanks to collaboration with our partners, we could now identify the mechanism and understand how a weak in-plane B-field establishes an equilibrium between these interactions, thereby altering the stripe state," says Ukleev.
The FNPP material is therefore suitable as a model system for externally controlling spin textures. The results obtained here advance the development of functional magnetic materials for spintronics.
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