Ordered Spin Ice State and Magnetic Fluctuations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Tb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Sn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:math>

Mirebeau, I.; Apetrei, A.; Rodrı́guez-Carvajal, J.; Bonville, P.; Forget, A.; Colson, D.; Glazkov, V. N.; Sanchez, Jean‐Pierre; Isnard, O.; Suard, Emmanuelle

doi:10.1103/physrevlett.94.246402

Cited by 156 publications

(153 citation statements)

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“…The hump at 1.1Å −1 is related to liquid-like correlations. A coexistence of short-range ferromagnetic and liquid-like correlations has also been observed in Tb 2 Sn 2 O 7 at 1.2 K, above its ordering temperature [24]. The fit to the data was achieved by combining a Lorentzian function and an antiferromagnetic nearest-neighbor spin correlation function.…”

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confidence: 89%

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Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

et al. 2014

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The origin of the spin liquid state in Tb2Ti2O7 has challenged experimentalists and theorists alike for nearly 20 years. To improve our understanding of the exotic magnetism in Tb2Ti2O7, we have synthesized a chemical pressure analog, Tb2Ge2O7. Germanium substitution results in a lattice contraction and enhanced exchange interactions. We have characterized the magnetic ground state of Tb2Ge2O7 with specific heat, ac and dc magnetic susceptibility, and polarized neutron scattering measurements. Akin to Tb2Ti2O7, there is no long-range order in Tb2Ge2O7 down to 20 mK. The Weiss temperature of −19.2(1) K, which is more negative than that of Tb2Ti2O7, supports the picture of stronger antiferromagnetic exchange. Polarized neutron scattering of Tb2Ge2O7 reveals that at 3.5 K liquid-like correlations dominate in this system. However, below 1 K, the liquid-like correlations give way to intense short-range ferromagnetic correlations with a length scale related to the Tb-Tb nearest neighbor distance. Despite stronger antiferromagnetic exchange, the ground state of Tb2Ge2O7 has ferromagnetic character, in stark contrast to the pressure-induced antiferromagnetic order observed in Tb2Ti2O7.Geometrically frustrated pyrochlores, R 2 M 2 O 7 , exhibit a diverse array of exotic magnetic behaviors [1]. The ground states in these materials are dictated by a complex, and often delicate balance of exchange, dipolar, and crystal field energies. Tb 2 Ti 2 O 7 is one of the most remarkable of these frustrated pyrochlores; strong antiferromagnetic exchange and Ising-like spins led to predictions of an antiferromagnetic Néel state below ∼1 K for this material [2]. However, experimental studies revealed a lack of static order or spin freezing in Tb 2 Ti 2 O 7 down to 70 mK [3,4], and more recently 57 mK [5]. Subsequently, enormous efforts have been undertaken to uncover the origin of the spin liquid state in Tb 2 Ti 2 O 7 .A further complication in Tb 2 Ti 2 O 7 is the coupling of magnetic and lattice degrees of freedom [6][7][8][9]. It has been suggested that hybridized magnetoelastic excitations may be responsible for the suppression of magnetic order in Tb 2 Ti 2 O 7 [10]. Another theoretical construct that attempts to account for the lack of static order in Tb 2 Ti 2 O 7 is a quantum spin ice state [11][12][13][14][15]. A third proposed scenario is that the non-Kramers doublet ground state of Tb 2 Ti 2 O 7 is split into two non-magnetic singlets through a symmetry reducing structural distortion [16][17][18].Other studies sought to uncover the origin of the spin liquid state in Tb 2 Ti 2 O 7 by focusing on mechanisms of its destruction, such as: external pressure [19], magnetic fields [18,20,21], and a combination of the two [22]. Partial antiferromagnetic order is induced in Tb 2 Ti 2 O 7 with external hydrostatic pressures of 8.6 GPa, resulting in a 1% compression of the lattice [19]. Another means of destroying the spin liquid state is chemical pressure: substitution of the non-magnetic titanium cation for an iso-electronic cation w...

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confidence: 89%

“…Substitution of titanium in Tb 2 Ti 2 O 7 for the larger tin cation allowed exploration of negative chemical pressure [23]. In Tb 2 Sn 2 O 7 , reduced antiferromagnetic exchange results in an "ordered spin ice" state at 0.87 K [23,24]. In this two-in, two-out state, the spins are oriented 13.3 • to the local <111> axes.…”

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Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

et al. 2014

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“…Besides these two canonical spin ices, other examples of spin-ice or spin-ice like ground state include Ho 2 Sn 2 O 7 [11] and T b 2 Sn 2 O 7 [12] members in the analogous stannate series, and, Nd 2 Mo 2 O 7 [13] and Sm 2 Mo 2 O 7 [14] in the molybdate pyrochlore series.…”

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confidence: 99%

Temperature-dependent Raman and x-ray studies of the spin-ice pyrochloreDy2Ti2O7and nonmagnetic pyrochlore

et al. 2008

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We present here temperature-dependent Raman, x-ray diffraction and specific heat studies between room temperature and 12 K on single crystals of spin-ice pyrochlore compound Dy 2 T i 2 O 7 and its non-magnetic analogue Lu 2 T i 2 O 7 . Raman data show a "new" band not predicted by factor group analysis of Raman-active modes for the pyrochlore structure in Dy 2 T i 2 O 7 , appearing below a temperature of T c =110 K with a concomitant contraction of the cubic unit cell volume as determined from the powder x-ray diffraction analysis. Low temperature Raman experiments on O 18 -isotope substituted Dy 2 T i 2 O 7 confirm the phonon origin of the "new" mode. These findings, absent in Lu 2 T i 2 O 7 , suggest that the room temperature cubic lattice of the pyrochlore Dy 2 T i 2 O 7 undergoes a "subtle" structural transformation near T c . We find anomalous red-shift of some of the phonon modes in both the Dy 2 T i 2 O 7 and the Lu 2 T i 2 O 7 as the temperature decreases, which is attributed to strong phonon-phonon anharmonic interactions.

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“…Then we searched for a solution in the tetragonal space group I4 1 /amd with the help of the program BasIreps of the FullProf suite [44]. Among the highest non-isomorphic subgroups of F d3m, this group is the only group simultaneously allowing ferromagnetic and antiferromagnetic components [45]. In contrast to the case of Yb 2 Sn 2 O 7 , no refinement according to this magnetic structure can account for the magnetic pattern of Yb 2 Ti 2 O 7 ; see the discussion section for more details.…”

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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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Ordered Spin Ice State and Magnetic Fluctuations inTb2Sn2O7

Cited by 156 publications

References 30 publications

Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

Temperature-dependent Raman and x-ray studies of the spin-ice pyrochloreDy2Ti2O7and nonmagnetic pyrochlore

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

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Ordered Spin Ice State and Magnetic Fluctuations inTb2Sn2O7

Cited by 156 publications

References 30 publications

Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

Incipient Ferromagnetism inTb2Ge2O7: Application of Chemical Pressure to the Enigmatic Spin-L

Temperature-dependent Raman and x-ray studies of the spin-ice pyrochloreDy2Ti2O7and nonmagnetic pyrochlore

A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

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A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇