Nonmagnetic impurities in skyrmion racetrack memory

Nucleation of magnetic skyrmions at a notch

“…5, with an increase in D, an intermediate minimum (inset 3) and a second maximum (inset 4) appear on the MEP, which becomes dominant. This process is similar to the process of nucleation of Sk on impurities, which we studied earlier [7]. It also occurred in two stages, first the creation of a skyrmion attached to the impurity, then its separation from the impurity.…”

“…In the article we focus on creation of Sk by employing a notch, which represents the nonmagnetic impurity located at the track boundary. In [22] we have demonstrated that Sk generation rate due to thermal perturbations is much smaller at the boundary than inside the track. Below we show that the Sk generation at a side of the track can be significantly improved by creating a notch.…”

“…Initial racetrack device was supposed to use domain wall (DW) as information carrier [1], but further research suggests that magnetic skyrmion (Sk) can be a better information carrier [3,4]. In particular, Sk has smaller chances to pin to impurities than DW, hence energy consumption of Sk based devices is smaller [5][6][7], moreover Sk velocity can even increase due to interaction with impurities [8]. Function of Sk racetrack memory device consists of creation of Sk on the track (writing bit), moving Sk along the track (register shift), detection of Sk (reading) and annihilation of Sk (erasing).…”

“…The Sk generation can be facilitated by geometry of the system [17]. In particular, Sk tends to easier appear on the impurities [7,[18][19][20][21] as a result certain impurities can be used for Sk generation provided means to remove Sk from such an impurity, e.g. spin-polarized current can be applied.…”