A reversible conversion between a skyrmion and a domain-wall pair in a junction geometry.

Skyrmions are expected to be a key component of the next-generation of spintronics: known as 'skyrmionics'. On the other hand, there is a well-established memory device encoded by a sequence of domain walls. Here we show a conversion is possible between a skyrmion and a domain-wall pair by connecting wide and narrow nanowires, enabling the information transmission between a skyrmion device and a domain-wall device. Our results will be the basis of a hybrid device made of skyrmions and domain walls, where the encoded information in domain walls is converted into skyrmions, and then read out by converting the skyrmions back to domain walls after a functional control of the skyrmions. Such a device has the potential to outperform domain-wall racetrack memory because of the combined advantages of domain walls and skyrmions for spintronics application.