Emergent magnetic monopoles, disorder, and avalanches in artificial kagome spin ice (invited)

Hügli, Remo V.; Duff, Gerard; O'Conchuir, B.; Mengotti, E.; Heyderman, Laura J.; Rodríguez, A. Fraile; Nolting, F.; Braun, Hans‐Benjamin

doi:10.1063/1.3670441

Cited by 26 publications

(22 citation statements)

References 37 publications

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“…As a result of the magnetic frustration, these systems can exhibit magnetic monopole type states, which are an example of an exotic emergent quasiparticle [280,299,300,301,302,303,304,305,306,307,308,309,310,311]. For example, magnetic monopoles and associated Dirac-like strings have been directly observed in the artificial honeycomb (on Co films of 20 nm thickness) and Kagome spin ice (permalloy films) systems [312,313,314] using magnetic force microscopy and X-ray photoemission microscopy.…”

Section: Artificial Spin Icementioning

confidence: 99%

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

Zvyagin

2013

Low Temperature Physics

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During recent years the interest to frustrated magnets has grown considerably. Such systems reveal very peculiar properties which distinguish them from standard paramagnets, magnetically ordered regular systems (like ferro-, ferri-, and antiferromagnets), or spin glasses. In particular great amount of attention has been devoted to the socalled spin ices, in which magnetic frustration together with the large value of the single-ion magnetic anisotropy of a special kind, yield peculiar behavior. One of the most exciting features of spin ices is related to low-energy emergent excitations, which, from many viewpoints can be considered as analogies of Dirac's monopoles. In this article we review the main achievements of theory and experiment in this field of physics.

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Section: Artificial Spin Icementioning

confidence: 99%

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

Zvyagin

2013

Low Temperature Physics

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“…This latter term plays the role of a charging energy or Hubbard-like on-site charge repulsion. The quantitative value for v 0 may be determined via matching the charge interaction of two neighbouring dumbbells with the dipolar interaction [8] or it may be evaluated directly via the micromagnetic interaction between the surface charges of the semicircular ends of two adjacent islands [17,24]. Equation (2.2) has several important consequences.…”

Section: Artificial Kagome Spin-ice Systemmentioning

confidence: 99%

Artificial kagome spin ice: dimensional reduction, avalanche control and emergent magnetic monopoles

Hügli

Duff

O'Conchuir

et al. 2012

Phil. Trans. R. Soc. A.

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Artificial spin-ice systems consisting of nanolithographic arrays of isolated nanomagnets are model systems for the study of frustration-induced phenomena. We have recently demonstrated that monopoles and Dirac strings can be directly observed via synchrotronbased photoemission electron microscopy, where the magnetic state of individual nanoislands can be imaged in real space. These experimental results of Dirac string formation are in excellent agreement with Monte Carlo simulations of the hysteresis of an array of dipoles situated on a kagome lattice with randomized switching fields. This formation of one-dimensional avalanches in a two-dimensional system is in sharp contrast to disordered thin films, where avalanches associated with magnetization reversal are twodimensional. The self-organized restriction of avalanches to one dimension provides an example of dimensional reduction due to frustration. We give simple explanations for the origin of this dimensional reduction and discuss the disorder dependence of these avalanches. We conclude with the explicit demonstration of how these avalanches can be controlled via locally modified anisotropies. Such a controlled start and stop of avalanches will have potential applications in data storage and information processing.

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“…For example, the extent of the strings is dependent on the amount of disorder given by the distribution in switching fields of the islands. A system with high disorder is characterized by short avalanches, whereas low disorder results in avalanches whose length approaches the sample size [71,74].…”

Section: Emergent Magnetic Monopolesmentioning

confidence: 99%

Artificial ferroic systems: novel functionality from structure, interactions and dynamics

Heyderman¹,

Stamps²

2013

J. Phys.: Condens. Matter

216

193

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Lithographic processing and film growth technologies are continuing to advance, so that it is now possible to create patterned ferroic materials consisting of arrays of sub-1 μm elements with high definition. Some of the most fascinating behaviour of these arrays can be realised by exploiting interactions between the individual elements to create new functionality. The properties of these artificial ferroic systems differ strikingly from those of their constituent components, with novel emergent behaviour arising from the collective dynamics of the interacting elements, which are arranged in specific designs and can be activated by applying magnetic or electric fields. We first focus on artificial spin systems consisting of arrays of dipolar-coupled nanomagnets and, in particular, review the field of artificial spin ice, which demonstrates a wide range of fascinating phenomena arising from the frustration inherent in particular arrangements of nanomagnets, including emergent magnetic monopoles, domains of ordered macrospins, and novel avalanche behaviour. We outline how demagnetisation protocols have been employed as an effective thermal anneal in an attempt to reach the ground state, comment on phenomena that arise in thermally activated systems and discuss strategies for selectively generating specific configurations using applied magnetic fields. We then move on from slow field and temperature driven dynamics to high frequency phenomena, discussing spinwave excitations in the context of magnonic crystals constructed from arrays of patterned magnetic elements. At high frequencies, these arrays are studied in terms of potential applications including magnetic logic, linear and non-linear microwave optics, and fast, efficient switching, and we consider the possibility to create tunable magnonic crystals with artificial spin ice. Finally, we discuss how functional ferroic composites can be incorporated to realise magnetoelectric effects. Specifically, we discuss artificial multiferroics (or multiferroic composites), which hold promise for new applications that involve electric field control of magnetism, or electric and magnetic field responsive devices for high frequency integrated circuit design in microwave and terahertz signal processing. We close with comments on how enhanced functionality can be realised through engineering of nanostructures with interacting ferroic components, creating opportunities for novel spin electronic devices that, for example, make use of the transport of magnetic charges, thermally activated elements, and reprogrammable nanomagnet systems.

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Emergent magnetic monopoles, disorder, and avalanches in artificial kagome spin ice (invited)

Cited by 26 publications

References 37 publications

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

New physics in frustrated magnets: Spin ices, monopoles, etc. (Review Article)

Artificial kagome spin ice: dimensional reduction, avalanche control and emergent magnetic monopoles

Artificial ferroic systems: novel functionality from structure, interactions and dynamics

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