Order and Frustration in Artificial Magnetic Patterns

Zabel, H.; Schumann, A.; Westphalen, A.; Remhof, Arndt

doi:10.12693/aphyspola.115.59

Cited by 12 publications

(16 citation statements)

References 19 publications

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“…The process then restarts and an avalanche develops. We emphasize again that there is no intentional symmetry breaking in these simulations and the origin of the directionality of the monopole motion is intrinsic and governed by its chirality at remanence [36] 7 .…”

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confidence: 85%

“…arrays of micro-and nanostructures provide an exciting playground in which the physics of magnetic frustration can be directly observed [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Through microscopy techniques, this approach offers the appealing opportunity to observe a wide range of phenomena within the concept of lab-on-a-chip and to test theoretical predictions from spin models.…”

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confidence: 99%

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Chiral nature of magnetic monopoles in artificial spin ice

et al. 2013

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Micromagnetic properties of monopoles in artificial kagome spin ice systems are investigated using numerical simulations. We show that micromagnetics brings additional complexity into the physics of these monopoles that is, by essence, absent in spin models: in addition to a fractionalized classical magnetic charge, monopoles in the artificial kagome ice are chiral at remanence. Our simulations predict that the chirality of these monopoles can be controlled without altering their charge state. This chirality breaks the vertex symmetry and triggers a directional motion of the monopole under an applied magnetic field. Our results also show that the choice of the geometrical features of the lattice can be used to turn on and off this chirality, thus allowing the investigation of chiral and achiral monopoles. S Online supplementary data available from stacks.iop.org/NJP/15/035026/ mmedia Modern developments in nanofabrication technology have recently enabled the investigation of fascinating phenomena in frustrated magnetic systems. After the work of Wang et al [1], a wave of studies focusing on artificial realizations of spin ice systems showed that patterned

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confidence: 85%

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confidence: 99%

Chiral nature of magnetic monopoles in artificial spin ice

et al. 2013

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“…These artificial magnetic compounds have the potential for increasing our understanding of disordered matter and may also lead to new technologies. Therefore, artificial spin ices are the object of intensive theoretical and experimental investigations [1][2][3][4][6][7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of elementary excitations in artificial magnetic square ice

et al. 2012

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We investigate the thermodynamics of artificial square spin ice systems assuming only dipolar interactions among the islands that compose the array. Emphasis is given to the effects of temperature on elementary excitations (magnetic monopoles and their strings). By using Monte Carlo techniques we calculate the specific heat, the density of poles and their average separation as functions of temperature. The specific heat and average separation between monopoles with opposite charges exhibit a sharp peak and a local maximum, respectively, at the same temperature, T p ≈ 7.2D/k B (here, D is the strength of the dipolar interaction and k B the Boltzmann constant). When the lattice size is increased, the amplitude of these features also increases but very slowly. Really, the specific heat and the maximum of the average separation d max between oppositely charged monopoles increase logarithmically with system size, indicating that completely isolated charges could be found only at the thermodynamic limit. In general, the results obtained here suggest that, for temperatures T T p , these systems may exhibit a phase with separated monopoles, although the quantity d max should not be larger than a few lattice spacings for viable artificial materials.

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“…The magnetocrystalline anisotropy of Permalloy (the magnetic material commonly used to fabricate artificial spin ice) is effectively zero, so that the shape anisotropy of each island forces its magnetic moment to align along the largest axis, making the islands effectively Ising-like. Actually, the fabrication and study of this kind of lower dimensional analogues of spin ice have received a lot of attention [9][10][11][12][13][14][15][16] . Indeed, the ability to manipulate the constituent degrees of freedom in condensed matter systems and their interactions is much important towards advanc- ing the understanding of a variety of natural phenomena.…”

Section: Introductionmentioning

confidence: 99%

Conditions for free magnetic monopoles in nanoscale square arrays of dipolar spin ice

2010

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We study a modified frustrated dipolar array recently proposed by Möller and Moessner [Phys. Rev. Lett. 96, 237202 (2006)], which is based on an array manufactured lithographically by Wang et al. [Nature (London) 439, 303 (2006)] and consists of introducing a height offset h between islands (dipoles) pointing along the two different lattice directions. The ground-states and excitations are studied as a function of h. We have found, in qualitative agreement with the results of Möller and Moessner, that the ground-state changes for h > h1, where h1 = 0.444a (a is the lattice parameter or distance between islands). In addition, the excitations above the ground-state behave like magnetic poles but confined by a string, whose tension decreases as h increases, in such a way that for h ≈ h1 its value is around 20 times smaller than that for h = 0. The system exhibits an anisotropy in the sense that the string tension and magnetic charge depends significantly on the directions in which the monopoles are separated. In turn, the intensity of the magnetic charge abruptly changes when the monopoles are separated along the direction of the longest axis of the islands. Such a gap is attributed to the transition from the anti to the ferromagnetic ground-state when h = h1.

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Order and Frustration in Artificial Magnetic Patterns

Cited by 12 publications

References 19 publications

Chiral nature of magnetic monopoles in artificial spin ice

Chiral nature of magnetic monopoles in artificial spin ice

Thermodynamics of elementary excitations in artificial magnetic square ice

Conditions for free magnetic monopoles in nanoscale square arrays of dipolar spin ice

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