Controlled modification of skyrmion information in a three-terminal racetrack memory

Manipulation of magnetic skyrmions has been generating considerable interest because of their potential applications in future spintronic devices. As an information carrier, a skyrmion is used to code a bit. In this work, we study via micromagnetic simulations a three-terminal racetrack memory, where an isolated skyrmion can be generated and annihilated by the gate voltage pulse. Thus, we can modify a train of skyrmion codes written at the generator in a controlled manner. The modified information is then detected at the collector. We have identified both gyration and breathing modes during skyrmion manipulation. The dynamics is analysed via a Thiele equation derived from the micromagnetic model. From the equation, the gyration mode of a skyrmion is suggested to be coupled to the breathing mode dynamics. This work proposes an effective method for controlled modification of skyrmion information in a potential energy-efficient racetrack memory, and provides a fundamental understanding of the intrinsic skyrmion dynamics during skyrmion manipulation.