Soft magnetic materials are characterized by their low coercivity — making them easy to magnetize and demagnetize — and high magnetic permeability, allowing magnetic fields to pass through with minimal resistance. Among them, soft magnetic fibres are promising for miniaturized, flexible systems. However, their limited flexibility restricts their ability to withstand repeated deformation, which restricts their broader applications. Producing micro-diameter fibres using simple methods has also been a persistent challenge. Now, writing in Nature Communications, Jiawei Li, Weiming Yang and colleagues propose an approach to fabricating micro-diameter soft magnetic fibres using high-entropy alloys (HEAs), overcoming the trade-off between mechanical strength and soft magnetic properties.

The resulting fibres display coarsened grains — larger crystalline regions — and fewer grain boundaries, which reduce the pinning of magnetic domain walls. This improvement facilitates magnetic domain wall movement and lowers the energy required to reorient the material’s magnetization.