Magnetic monopoles in spin ice

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.

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“Color-Tripole Ice” as a Conceptual Generalization of “Spin Ice”

Journal of Materials ◽

10.1155/2013/836168 ◽

2013 ◽

Vol 2013 ◽

pp. 1-16 ◽

Cited By ~ 1

Author(s):

Chia-Ren Hu

Keyword(s):

High Energy Physics ◽

Zero Point ◽

High Energy ◽

Magnetic Monopoles ◽

Spin Ice ◽

Elementary Excitations ◽

Magnetic Dipoles ◽

Frustrated Magnet ◽

Statistical Mechanical ◽

Energy Physics

“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.

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Electric dipoles on magnetic monopoles in spin ice

Nature Communications ◽

10.1038/ncomms1904 ◽

2012 ◽

Vol 3 (1) ◽

Cited By ~ 46

Author(s):

D.I. Khomskii

Keyword(s):

Magnetic Monopoles ◽

Spin Ice ◽

Electric Dipoles

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ChemInform Abstract: Dirac Strings and Magnetic Monopoles in the Spin Ice Dy2Ti2O7.

ChemInform ◽

10.1002/chin.200951014 ◽

2009 ◽

Vol 40 (51) ◽

pp. no-no ◽

Cited By ~ 1

Author(s):

D. J. P. Morris ◽

et al. et al.

Keyword(s):

Magnetic Monopoles ◽

Spin Ice

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A Model of Two Quantum Fluids for the Low Energy Excited States of the Systems with Entities That Mimic the Magnetic Monopoles

Fluids ◽

10.3390/fluids6090324 ◽

2021 ◽

Vol 6 (9) ◽

pp. 324

Author(s):

Fernando M. López-Aguilar ◽

Fernando I. López-Bara

Keyword(s):

Specific Heat ◽

Excited States ◽

Magnetic Monopoles ◽

Low Energy ◽

Quantum Fluids ◽

Spin Ice ◽

Energy Excitation ◽

Magnetic Dipoles ◽

Plasma State ◽

Good Concordance

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.

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Thermally and field-driven mobility of emergent magnetic charges in square artificial spin ice

Scientific Reports ◽

10.1038/s41598-019-52460-7 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Sophie A. Morley ◽

Jose Maria Porro ◽

Aleš Hrabec ◽

Mark C. Rosamond ◽

Diego Alba Venero ◽

...

Keyword(s):

Critical Field ◽

Magnetic Monopoles ◽

Model Systems ◽

Square Lattice ◽

Creep Model ◽

Spin Ice ◽

One Dimensional ◽

X Ray ◽

Drift Motion ◽

Artificial Spin Ice

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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