Limitations in artificial spin ice path selectivity: the challenges beyond topological control

Abstract

Magnetic charge is carried through nanowire networks by domain walls, and the micromagnetic structure of a domain wall provides an opportunity to manipulate its movement. We have shown previously that magnetic monopole defects exist in artificial spin ice (ASI) and result from two bar switching at a vertex. To create and manipulate monopole defects and indeed magnetic charge in general, path selectivity of the domain wall at a vertex is required. We have recently shown that in connected ASI structures, transverse wall chirality (or topology) determines wall path direction, but a mechanism known as Walker breakdown, where a wall mutates into a wall of opposite chirality partially destroys selectivity. Recently it has been claimed that in isolated Y-shaped junctions that support vortex walls, selectivity is entirely determined by chirality (or topology), the suggestion being that vortex wall chirality is robust in the Walker breakdown process. Here we demonstrate that in Yshaped junctions, magnetic switching in the important topologically protected regime exists only for a narrow window of field and bar geometry, and that it will be challenging to access this regime in fielddriven ASI. This work has implications for the wider field of magnetic charge manipulation for high density memory storage.

Magnetization dynamics of topological defects and the spin solid in a kagome artificial spin ice

“…So far, global magnetic fields were typically considered to manipulate topological defects and thereby explore the path selectivity of evolving Dirac strings [8,13,29]. Our results offer a novel method to modify topological defects deterministically.…”

Angular-dependent magnetization reversal processes in artificial spin ice

“…10 The field driven manipulation of pre-existing DWs in connected artificial spin ice systems is governed by the chirality and topological nature of the DW 11,12 and it's time-evolution during dynamic propagation. 13,14 These DWs typically originate at the edges of the sample as the reversal in the center of the array is constrained by the magnetization of the surrounding bars. 15 Therefore, the magnetization reversal in one bar triggers the reversal in neighbouring bars and leads to chains of reversal following Dirac strings in avalanche-like behavior.…”

Understanding magnetotransport signatures in networks of connected permalloy nanowires

“…Artificial spin ice structures have proven to be exemplary 35 systems in which to study frustration [5,6] and have been noted for their technological 36 potential as both a reconfigurable metamaterial and as a memory storage medium [7,8,37 9, 10,11,12]. Connected artificial spin ice in particular has been studied extensively in 38 the last decade [13,14,15,16,17,18,19,20,21,22,23,24,25]. Tanaka et al and 39 other workers, observed sharp features in the magnetoresistance of connected artificial 40 spin ice, and associated them with reversal events that maintain the ice rules of the 41 system [13,14,15].…”