Emergent dynamic chirality in a thermally driven artificial spin ratchet

Abstract

Modern nanofabrication techniques have opened the possibility to create novel functional materials, whose properties transcend those of their constituent elements. In particular, tuning the magnetostatic interactions in geometrically frustrated arrangements of nanoelements called artificial spin ice can lead to specific collective behaviour, including emergent magnetic monopoles, charge screening and transport, as well as magnonic response. Here, we demonstrate a spin-ice-based active material in which energy is converted into unidirectional dynamics. Using X-ray photoemission electron microscopy we show that the collective rotation of the average magnetization proceeds in a unique sense during thermal relaxation. Our simulations demonstrate that this emergent chiral behaviour is driven by the topology of the magnetostatic field at the edges of the nanomagnet array, resulting in an asymmetric energy landscape. In addition, a bias field can be used to modify the sense of rotation of the average magnetization. This opens the possibility of implementing a magnetic Brownian ratchet, which may find applications in novel nanoscale devices, such as magnetic nanomotors, actuators, sensors or memory cells.

Apparent ferromagnetism in the pinwheel artificial spin ice

“…However, the discrete geometry considered here has interesting consequences on ordering processes [14], which we explore in this paper. For instance, one of the possible pinwheel tillings has been recently studing by Gliga and co-wrkers who showed how dynamic chirality can emerge in these structures and how a ferromagnetic ordering is favoured [15]. We examine the effect of array geometries on stable and meta-stable configurations of mesoscopic domains and how their growth is mediated by 'wall-like' boundaries.…”

Understanding thermal annealing of artificial spin ice

“…This thickness dependence of the permalloy T C has clear implications for artificial spin ice studies. For example, the suppressed T C for thinner films is directly relevant to the many photoelectron emission microscopy (PEEM) measurements that have been conducted on permalloy artificial spin ice 5,8,22,23 . Those measurements focused on films of thickness around 3 nm, and they are therefore conducted relatively close to T C of the substituent ferromagnetic material.…”

Colloquium : Ice rule and emergent frustration in particle ice and beyond

“…1(b,c). Soon, a growing number of groups began using ASI to investigate topological defects, the dynamics of magnetic charges, and spin fragmentation Ladak et al, 2011aLadak et al, ,b, 2010Mengotti et al, 2011;Phatak et al, 2011;Pollard et al, 2012;Rougemaille et al, 2011;Zeissler et al, 2013), as well as information encoding (Wan, 2016;Lammert et al, 2010), equilibrium and nonequilibrium thermodynamics (Budrikis et al, 2013(Budrikis et al, , 2011Chioar et al, 2014a,a;Cugliandolo, 2017;Ke et al, 2008;Lammert et al, 2012;Levis et al, 2013;Morgan et al, 2011;Nisoli et al, 2010Nisoli et al, , 2007, avalanches (Hügli et al, 2012;Shen et al, 2011), direct realizations of the Ising system (Arnalds et al, 2016;Chioar et al, 2016Chioar et al, , 2014bNisoli, 2016;Zhang et al, 2012), magnetoresistance and the Hall effect (Branford et al, 2012;Le et al, 2017), critical slowing down (Anghinolfi et al, 2015), dislocations (Drisko et al, 2017), spin wave excitations (Gliga et al, 2013), ratchet effects (Gliga et al, 2017), dimensionality reduction (Gilbert et al, 2016a), classical topological states (Gilbert et al, 2014;Lao et al, 2018;Perrin et al, 2016), quasi-crystals (Barr...…”

“…Artificial spin ice systems were first created by mimicking natural frustrated geometries and by realizing celebrated models of statistical mechanics (Baxter, 1982;Lieb, 1967b) in settings that allowed characterization at the constituent level, often in real time. However, since artificial materials can be realized in various geometries, a more recent effort (Morrison et al, 2013;Nisoli et al, 2017) has advanced the design of new systems generating a wide variety of new phenomena, including dimensionality reduction, emergent classical topological order, realizations of Pott's models, phase transitions, ice rule fragility, and quasi-crystal spin ices (Barrows et al, 2019;Gilbert et al, 2014Gilbert et al, , 2016aGliga et al, 2017;Lao et al, 2018;Louis et al, 2018;Ma et al, 2016;Östman et al, 2017;Perrin et al, 2016;Shi et al, 2018;Sklenar et al, 2019). Furthermore, many of these ideas proved to be exportable across different platforms, from nanomagnets to trapped colloids, to liquid crystals, and to superconductors (Duzgun and Nisoli, 2019;Latimer et al, 2013;Libál et al, 2009;Ortiz-Ambriz and Tierno, 2016;Wang et al, 2018).…”