Higgs transition from a magnetic Coulomb liquid to a ferromagnet in Yb2Ti2O7

Chang, Liang; Onoda, Shigeki; Su, Yixi; Kao, Ying-Jer; Tsuei, Ku Ding; Yasui, Yukihiko; Kakurai, Kazuhisa; Lees, Martin R.

doi:10.1038/ncomms1989

Cited by 206 publications

(362 citation statements)

References 45 publications

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“…The residual difference could be tentatively assigned to short-range magnetic correlations observed in several instances [31,49,32], while the diffraction experiment reported here only picks up the long-range ordered component. The signature of these short-range correlations seems to disappear below T c [31], but they are still observed in µSR data [49].…”

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confidence: 91%

“…Here we report the observation of magnetic Bragg reflections at 60 mK by powder neutron diffraction for the titanate and the determination of its magnetic structure. The result of the analysis is based on crystal symmetry and is at variance with the previously proposed nearly collinear ferromagnetic structure [27,31].…”

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confidence: 91%

“…The magnetization curves along the [100] and [110] directions have been determined [48]. Polarized neutron scattering on crystals shows the presence of a diffuse [111]-rod of scattering and pinch-point features which develop on cooling [31]. These features are suppressed at T c .…”

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confidence: 99%

“…Alternatively the coherent magnetic order could be so disrupted by crystal defects that any magnetic Bragg reflections would be too broad to be observable [26]. Due to the long-standing controversy as to the presence of magnetic Bragg reflections [22,27,28,29,30,31,32], the magnetic nature of the ground state of Yb 2 Ti 2 O 7 at low temperature is still uncertain. Magnetic Bragg reflections are reported only in Refs.…”

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confidence: 99%

“…[27,31] which describe data measured on the same crystal. The diversity of the specific heat [33,34,31,35] and muon spin relaxation (µSR) results [22,36,25,23] adds to the difficulty in understanding the ground state. In addition to the sample quality issue first noticed in Ref.…”

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confidence: 99%

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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: 91%

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confidence: 91%

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confidence: 99%