Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing

Abstract

Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing-a scanning probe technique-provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy 'monopole-chain' states that exhibit negative effective temperatures.

Realization of the kagome spin ice state in a frustrated intermetallic compound

“…Moreover, in all three structures the spins are always reversed in such a way that the one-in-two-out or twoin-one-out ice rule is satisfied, but the total magnetic moment along b increases with increasing field. At H=4T, the magnetic unit cell becomes identical to the structural unit cell (14,15,18), and has the largest possible net moment allowed by the ice rule. This is further corroborated by the identical magnetization jump of 1.7μB/Ho at the three metamagnetic transitions at 1.8K ( Fig.…”

“…Experimentally, kagome spin ices have only been realized in artificial spin ice systems formed by nanorods of ferromagnets organized into honeycomb networks (12)(13)(14)(15)(16)(17)(18). However, the large magnetic energy scales and system sizes make it challenging to explore the rich phase diagram of spin ices in the thermodynamic limit (17,18). Alternatively, kagome ice behavior has been reported in pyrochlore spin ices such as Dy2Ti2O7 and Ho2Ti2O7 under magnetic field along the [111] direction (19)(20)(21).…”

Advances in artificial spin ice

“…To circumvent these effects, the geometry of the Y-junctions can be modified so that the symmetry of the branches is reduced, giving a deterministic domain wall path that is independent of the domain-wall chirality 69 . It is also possible to nucleate domain walls in particular positions in connected artificial spin ice using a magnetic tip such as that found in a magnetic force microscope (MFM), thereby creating specific magnetic configurations at will 70 . Finally, just as the chirality of the domain walls provides additional degrees of freedom in connected artificial spin systems, the edge bending of the magnetization at the vertices in disconnected lattices also gives an additional chiral degree of freedom to the vertex monopoles 71 (Fig.…”

Observation of transient states during magnetization reversal in a quasicrystal artificial spin ice

“…Additionally, a new approach to observing ASIs in higher energy states has been described in work by Gartside et al, in which they describe how topological defect-driven magnetic writing can be used to access the entire range of possible microstates in Kagome ASI. 12 There has also been interest in studying the magnetization reversal in Kagome ASIs that are composed of connected magnetic bars rather than discrete islands. In these connected ASIs, the reversal is strongly influenced by the motion of domain walls throughout the ASI, particularly in the central vertex region connecting the magnetic bars.…”