Magnetic monopoles in spin ice

Castelnovo, Claudio; Moessner, Roderich; Sondhi, S. L.

doi:10.1038/nature06433

Cited by 1,391 publications

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“…It is characterized by dipolar correlations emerging from the topological spin-ice constraint. This translates into pinch-points in the neutron diffuse scattering patterns [11] and magnetic monopole excitations [12,13,14].Because of its large ground-state degeneracy, a spin-ice compound does not order magnetically, i.e., it is in a so-called spin liquid state where the spins are strongly correlated although they do not display long range order. Quantum fluctuations are not expected to play a significant role for Ho 2 Ti 2 O 7 .…”

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confidence: 99%

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

Yaouanc

Réotier

Keller

et al. 2016

J. Phys.: Condens. Matter

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Abstract. The pyrochlore insulator Yb 2 Ti 2 O 7 has attracted the attention of experimentalists and theoreticians alike for about 15 years. Conflicting neutron diffraction data on the possible existence of magnetic Bragg reflections at low temperature have been published. Here we report the observation of magnetic Bragg reflections by neutron powder diffraction at 60 mK. The magnetic diffraction pattern is analyzed using representation theory. We find Yb 2 Ti 2 O 7 to be a splayed ferromagnet as reported for Yb 2 Sn 2 O 7 , a sibling compound with also dominating ferromagnetic interactions as inferred from the positive Curie-Weiss temperature. However, the configuration of the magnetic moment components perpendicular to the easy axis is of the all-in-all-out type in Yb 2 Ti 2 O 7 while it is two-in-two-out in Yb 2 Sn 2 O 7 . An overall experimental picture of the magnetic properties emerges. Introduction -The broad interest in geometrically frustrated magnetic materials such as pyrochlore insulator compounds R 2 M 2 O 7 (F d3m space group), where R is a rare earth ion and M a non magnetic element, arises from the large diversity of magnetic ground states and exotic fluctuations and excitations encountered [1,2,3,4,5]. This is due to the combined effects of the geometrical constraint resulting from the topology of the pyrochlore lattice and the action of the different possible interactions. As a consequence, classical and quantum fluctuations are particularly strong. Among the interactions of interest, the crystal field at the R position, the Heisenberg nearest-neighbour exchange interaction as well as its extension beyond the nearest-neighbour R ions [6,7], the anisotropy of the exchange interactions [8,9] and the inevitable dipolar interactions have been considered.The most remarkable discovery in the realm of geometrically frustrated magnetic materials has been the spin-ice ground state of Ho 2 Ti 2 O 7 in 1997 [10]. It is characterized by dipolar correlations emerging from the topological spin-ice constraint. This translates into pinch-points in the neutron diffuse scattering patterns [11] and magnetic monopole excitations [12,13,14].Because of its large ground-state degeneracy, a spin-ice compound does not order magnetically, i.e., it is in a so-called spin liquid state where the spins are strongly correlated although they do not display long range order. Quantum fluctuations are not expected to play a significant role for Ho 2 Ti 2 O 7 . However, for some pyrochlore materials strong quantum transverse fluctuations [8,9] could stabilize new magnetic states such as a quantum spin liquid for which new exotic excitations are expected [3,15,16,17,5].One of the favourite candidates for this exotic ground state is Yb 2 Ti 2 O 7 . Indeed, the exchange interactions are highly anisotropic, with a strong ferromagnetic component akin to the Ising exchange of spin ice [18].The dominating ferromagnetic component is also suggested by the positive Curie-Weiss temperature [19]. Remarkably, the Ising character of the exchan...

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confidence: 99%

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

Yaouanc

Réotier

Keller

et al. 2016

J. Phys.: Condens. Matter

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“…However, this local constraint, called ice rule [9], is insufficient to establish a long-range order, and results in the macroscopic degeneracy in the ground state. In addition, the long-range dipolar interactions lead to significant changes in the phase diagram [10] and emergence of peculiar excitation called magnetic monopoles [11,12].…”

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confidence: 99%

Monte Carlo Study of an Effective Ising Model for the Spin-Ice Type Kondo Lattice Model

Ishizuka

Udagawa²,

Motome³

2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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An effective Ising model for the spin-ice type Kondo lattice model is investigated by the classical Monte Carlo simulation. We clarify the magnetic phase diagram with four phases: ice-ferro, ice-(0, 0, 2π), 32-sublattice, and all-in/all-out ordered states. The result well reproduces the phase diagram of the Kondo lattice model studied previously [H. Ishizuka et al.: J. Phys. Soc. Jpn. 81 (2012) 113706], which suggests that the RKKY interactions up to third neighbors are sufficient to describe the magnetic properties of the itinerant electron model. We discuss the peculiar nature of phase transitions: the suppression of the critical temperatures down to zero temperature between two ice phases and the presence of the tricritical points on the phase boundary of the 32-sublattice ordered state.

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“…These constrains stabilize the so-called "two-in, two-out" state of each tetrahedron, leading to a highly-degenerated state on a pyrochlore lattice characterized by the Pauling residual entropy. Moreover, the emergence of the monopolar defect, created by a single spin flip from the two-in, two-out ground manifold, has attracted much attention [5]. Reflecting the classical nature of the dipolar couplings, magnetic behaviors of dipolar spin ice can be well approximated by a so-called dipolar spin ice model which does not include any quantum fluctuations, and thus the associated dynamics completely freezes at low temperatures [6].…”

Section: Introductionmentioning

confidence: 99%

Magnetic and Thermal Properties of the Single Crystalline Pr₂Zr₂O₇ in a [111] Field

Kimura¹,

Nakatsuji²

2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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We report the experimental results of magnetic and thermal properties of the single crystalline pyrochlore magnet Pr 2 Zr 2 O 7 , a new class of spin ice system based on exchange interactions. Under zero magnetic field, specific heat shows a broad peak around 1.5 K, associated with the spin ice formation. Under the field of 9 T along the [111] direction, on the other hand, the specific heat forms two broad peaks at temperatures of 3 K and 10 K. These peaks are attributable to the different size of Zeeman splittings of spins on a kagomé and triangular planes with the assumption of the large Ising anisotropy along the [111] direction. Quantum fluctuations in this system are also discussed based on the specific heat data.

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Magnetic monopoles in spin ice

Cited by 1,391 publications

References 23 publications

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

Monte Carlo Study of an Effective Ising Model for the Spin-Ice Type Kondo Lattice Model

Magnetic and Thermal Properties of the Single Crystalline Pr₂Zr₂O₇ in a [111] Field

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Magnetic monopoles in spin ice

Cited by 1,391 publications

References 23 publications

A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

Monte Carlo Study of an Effective Ising Model for the Spin-Ice Type Kondo Lattice Model

Magnetic and Thermal Properties of the Single Crystalline Pr2Zr2O7 in a [111] Field

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A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

Magnetic and Thermal Properties of the Single Crystalline Pr₂Zr₂O₇ in a [111] Field