Real-space observation of emergent magnetic monopoles and associated Dirac strings in artificial kagome spin ice

2010 ◽  
Vol 7 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Elena Mengotti ◽  
Laura J. Heyderman ◽  
Arantxa Fraile Rodríguez ◽  
Frithjof Nolting ◽  
Remo V. Hügli ◽  
...  
2019 ◽  
Vol 5 (2) ◽  
pp. eaav6380 ◽  
Author(s):  
Alan Farhan ◽  
Michael Saccone ◽  
Charlotte F. Petersen ◽  
Scott Dhuey ◽  
Rajesh V. Chopdekar ◽  
...  

Magnetic monopoles, proposed as elementary particles that act as isolated magnetic south and north poles, have long attracted research interest as magnetic analogs to electric charge. In solid-state physics, a classical analog to these elusive particles has emerged as topological excitations within pyrochlore spin ice systems. We present the first real-time imaging of emergent magnetic monopole motion in a macroscopically degenerate artificial spin ice system consisting of thermally activated Ising-type nanomagnets lithographically arranged onto a pre-etched silicon substrate. A real-space characterization of emergent magnetic monopoles within the framework of Debye-Hückel theory is performed, providing visual evidence that these topological defects act like a plasma of Coulomb-type magnetic charges. In contrast to vertex defects in a purely two-dimensional artificial square ice, magnetic monopoles are free to evolve within a divergence-free vacuum, a magnetic Coulomb phase, for which features in the form of pinch-point singularities in magnetic structure factors are observed.


Author(s):  
R. V. Hügli ◽  
G. Duff ◽  
B. O'Conchuir ◽  
E. Mengotti ◽  
A. Fraile Rodríguez ◽  
...  

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 synchrotron-based 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 two-dimensional. 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.


Nature ◽  
2008 ◽  
Vol 451 (7174) ◽  
pp. 42-45 ◽  
Author(s):  
C. Castelnovo ◽  
R. Moessner ◽  
S. L. Sondhi
Keyword(s):  

Author(s):  
Alexandra Schumann ◽  
Hartmut Zabel

Artificial dipolar spin-ice patterns have attracted much attention recently because of their rich configurations and excitations in the form of Dirac strings connecting magnetic monopoles. We have analysed the distribution of excitations in the form of strings and vertices carrying magnetic charges Q =±3 q in honeycomb artificial spin-ice patterns. Two types of patterns are compared, those that terminate with open hexagons and those with closed hexagons. The dipole configurations and the frequency of spin-ice rule-violating Q =±3 q vertices depend slightly on the boundary conditions of the pattern. Upon rotation of the patterns by 2 π in a coercive magnetic field of 500 Oe, complete reversibility of the charge and string configuration is observed.


2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Chia-Ren Hu

“Spin Ice” is an exotic type of frustrated magnet realized in “pyrochlore” materials Ho2Ti2O7, Dy2Ti2O7, Ho2Sn2O7, and so forth, in which magnetic atoms (spins) reside on a sublattice made of the vertices of corner-sharing tetrahedra. Each spin is Ising-like with respect to a local axis which connects the centers of two tetrahedra sharing the vertex occupied by the spin. The macroscopically degenerate ground states of these magnets obey the “two-in two-out” “ice rule” within each tetrahedron. Magnetic monopoles and antimonopoles emerge as elementary excitations, “fractionalizing” the constituent magnetic dipoles. This system is also a novel type of statistical mechanical system. Here we introduce a conceptual generalization of “spin ice” to what we shall call “color-tripole ice,” in which three types of “color charges” can emerge as elementary excitations, which are Abelian approximations of the color charges introduced in high energy physics. Two two-dimensional (2D) models are introduced first, where the color charges are found to be 1D and constrained 2D, respectively. Generalizations of these two models to 3D are then briefly discussed. In the second one the color charges are likely 3D. Pauling-type estimates of the “residual (or zero-point) entropy” are also made for these models.


ChemInform ◽  
2009 ◽  
Vol 40 (51) ◽  
pp. no-no ◽  
Author(s):  
D. J. P. Morris ◽  
et al. et al.
Keyword(s):  

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 324
Author(s):  
Fernando M. López-Aguilar ◽  
Fernando I. López-Bara

The low energy excitation states in frustrated magnetic structures can generate quasiparticles that behave as if they were magnetic charges. These excited states produce, in the so-called spin-ice materials, two different peaks of specific heat at temperatures less than 1.5 K. In this paper, we consider that the first structure is caused by the formation of fluid of magnetic dipoles configured by the dumbbell model with a boson nature in consonance with that described by Witten for mesons. The second structure, wider than the first one, corresponds to a plasma state that comes from the breaking of a great number of dipoles, which provokes the appearance of free magnetic charges, which constitute a cool magnetic plasma fluid. In this paper, we determine thermodynamic analytical functions: the thermo-potential and internal energy and their respective derivative physical magnitudes: entropy, and magnetic specific heat. We obtain results in a good concordance with the experimental data, which allow us to explain the phase transitions occurred in these spin-ice materials at very low temperatures.


Author(s):  
Rajan Iyer

This article will continue ansatz gage matrix of Iyer Markoulakis Helmholtz Hamiltonian mechanics points’ fields gage to Pauli Dirac monopole particle fields ansatz gage general formalism at Planck level, by constructing a Pauli Dirac Planck circuit matrix field gradient of particle monopole flow loop. This circuit assembly gage (PDPcag) that maybe operating at the quantum level, demonstrates the power of point fields matrix theoretical quantum general formalism of Iyer Markoulakis Helmholtz Hamiltonian mechanics transformed to Coulomb gage metrics, to form eigenvector fields of magnetic monopoles as well as electron positron particle gage metrics fields. Eigenvector calculations performed based on Iyer Markoulakis quantum general formalism are substituted for gage values of typical eigenvectors of dipolar magnetically biased monopoles with their conjugate eigenvectors, as well as eigenvector fields that are of the electron and positron particles. Then they are compiled to form combinatorial eigenvector matrix bundle of the monopole particle circuit field constructs assembly. Evaluation of this monopole particle fields matrix provided eigenvector fields results like SUSY, having Hermitian quantum matrix with electron-positron annihilation alongside north and south monopoles collapsing to dipolar “stable” magnetism, representing electromagnetic gaging typical metrics fields. Applying experimental observations on magnetic poles with measuring magnetic forces John Hodge’s results were showing asymmetrical pole forces; author has mathematically constructed asymmetric\strings\gage\metrics to characterize electromagnetic gravity, putting together while integrating with stringmetrics gravity that author has been reporting in earlier published articles. Physical Analysis with generalization of mass-charge and charge-fields gage metrics to quantum relativity gage metrics fields are proposed based on author’s proof formalism paper providing derivational algorithmic steps, to determine gage parametric values within the equation of Coulomb gage. Vortex fields’ wavefunctions and the scalar potential characterized by a function and a coupling constant having quantum density matrix together define the gage metrics quantifiable observable measurement physics of electron-positron cross-diagonal fields; contrastingly, diagonal terms of PDPcag matrix characterizes electron-positron particle eigenvector fields, while Hilbert Higgs mass metrics characterizes eigen-matter. Author is already working with Christopher O’Neill about magic square symmetry configurations to quantitatively understand symmetry, structure, and the real space geometry that are expected to form out of vacuum quanta point fields’ quantitative quantum general formalism theory of Iyer Markoulakis. In addition, author is currently collaborating with Manuel Malaver’s astrophysical Einstein Minkowski modified space time metrics evaluations of the sense-time-space relativistic general metrics to have means to account for curving or shaping of spacetime topology of a five-dimensional sense-time-space. Manuel Malaver’s specialization with modified Einstein Maxwell equations for modeling galaxies and stars cosmological physics, utilizing Einstein-Maxwell-Tolman- Schwarzschild and Reissner-Nordström spacetime and black holes theoretical formalisms have author of this paper collaboratively model quantum astrophysics of dark energy Star’s theory with Einstein-Gauss-Bonnet gravity equations.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Sophie A. Morley ◽  
Jose Maria Porro ◽  
Aleš Hrabec ◽  
Mark C. Rosamond ◽  
Diego Alba Venero ◽  
...  

Abstract Designing and constructing model systems that embody the statistical mechanics of frustration is now possible using nanotechnology. We have arranged nanomagnets on a two-dimensional square lattice to form an artificial spin ice, and studied its fractional excitations, emergent magnetic monopoles, and how they respond to a driving field using X-ray magnetic microscopy. We observe a regime in which the monopole drift velocity is linear in field above a critical field for the onset of motion. The temperature dependence of the critical field can be described by introducing an interaction term into the Bean-Livingston model of field-assisted barrier hopping. By analogy with electrical charge drift motion, we define and measure a monopole mobility that is larger both for higher temperatures and stronger interactions between nanomagnets. The mobility in this linear regime is described by a creep model of zero-dimensional charges moving within a network of quasi-one-dimensional objects.


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