Experimental Insights into Ground-State Selection of Quantum XY Pyrochlores

Hallas, Alannah; Gaudet, Jonathan; Gaulin, B. D.

doi:10.1146/annurev-conmatphys-031016-025218

Cited by 74 publications

(88 citation statements)

References 143 publications

(232 reference statements)

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“…Recently, growing interest has been devoted to magnetic pyrochlores with the complementary form of anisotropy, local XY anisotropy where the spins are constrained to point in a plane perpendicular to the local Ising axis [7]. XY pyrochlore magnets, such as Yb 2 Ti 2 O 7 and Er 2 Ti 2 O 7 , possess an effective S = 1/2 degree of freedom [8,9].…”

Section: +mentioning

confidence: 99%

Effect of chemical pressure on the crystal electric field states of erbium pyrochlore magnets

et al. 2018

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We have carried out a systematic study of the crystal electric field excitations in the family of cubic pyrochlores Er2B2O7, with B = Ge, Ti, Pt, and Sn, using neutron spectroscopy. All members of this family are magnetic insulators based on 4f11 Er 3+ and non-magnetic B 4+ . At sufficiently low temperatures, long-range antiferromagnetic order is observed in each of these Er2B2O7 pyrochlores. Our inelastic neutron scattering measurements probe the transitions from the ground state doublet to excited crystal electric field states belonging to the J = 15/2 Hund's rules manifold. This allows us to quantitatively determine the energy eigenvalues and eigenfunctions of these (2J + 1) = 16 states across the Er2B2O7 series. The different ionic sizes associated with different non-magnetic B 4+ cations correspond to positive or negative chemical pressure, depending on the relative contraction or expansion of the crystal lattice, which gives rise to different local environments at the Er 3+ site. Our results show that the g-tensor components are XY-like for all four members of the Er2B2O7 series. However, the XY anisotropy is much stronger for Er2Pt2O7 and Er2Sn2O7 ( g ⊥/g z > 25), than for Er2Ge2O7 and Er2Ti2O7 ( g ⊥/g z < 4). The variation in the nature of the XY-anisotropy in these systems correlates strongly with their ground states, as Er2Ge2O7 and Er2Ti2O7 order into Γ5 magnetic structures, while Er2Pt2O7 and Er2Sn2O7 order in the Γ7 Palmer-Chalker structure.

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Section: +mentioning

confidence: 99%

Effect of chemical pressure on the crystal electric field states of erbium pyrochlore magnets

et al. 2018

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“…(5)], the gaugeenriched group relations in Eq. (14) can be rewritten as (20) transforming the phases φ Oi ( r µ ) according to…”

Section: Using the General Conjugation Rulementioning

confidence: 99%

Competing orders in pyrochlore magnets from a Z2 spin liquid perspective

Liu

Halász

2019

Phys. Rev. B

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The pyrochlore materials have long been predicted to harbor a quantum spin liquid, an intrinsic long-range-entangled state supporting fractionalized excitations. Existing pyrochlore experiments, on the other hand, have discovered several weakly ordered states and a tendency of close competition amongst them. Motivated by these facts, we give a complete classification of spin-orbit-coupled Z2 spin-liquid states on the pyrochlore lattice by using the projective symmetry group (PSG) approach for bosonic spinons. For each spin liquid, we construct a mean-field Hamiltonian that can be used to describe phase transitions out of the spin liquid via spinon condensation. Studying these phase transitions, we establish phase diagrams for our mean-field Hamiltonians that link magnetic orders to specific spin liquids. In general, we find that seemingly unrelated magnetic orders are intertwined with each other and that the conventional spin orders seen in the experiments are accompanied by more exotic hidden orders. Our critical theories are categorized into z = 1 and z = 2 types, based on their spinon dispersion and Hamiltonian diagonalizability, and are shown to give distinct signatures in the heat capacity and the spin structure factor. This study provides a clear map of pyrochlore phases for future experiments and variational Monte Carlo studies in pyrochlore materials. arXiv:1905.00460v2 [cond-mat.str-el]

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“…RE ions in the crystal lattice of the pyrochlore (space group Fd3m ) occupy 16d Wyckoff positions with the local trigonal symmetry D 3d . Four magnetically non-equivalent RE sublattices form a corner-sharing tetrahedral network, the basis vectors of RE 3+ ions in the unit cell in the crystallographic system of coordinates with the origin at the center of a corresponding tetrahedron are as follows: 1 (1,1,1) / 8  r , 2 ( 1, 1,1) / 8    r , 3 ( 1,1, 1) / 8    r , 4 (1, 1, 1) / 8    r in the units of the lattice constant a . The first coordination shell of RE ions contains eight oxygen ions which form strongly distorted cubic polyhedron with the two nearest neighbor oxygen ions at one of the four crystallographic [111] axes.…”

Section: Introductionmentioning

confidence: 99%

“…The CF approach serves as a basis for construction of theoretical models of interactions between RE ions and a crystal lattice and for understanding of magnetic properties of concentrated RE compounds. A number of CF parameter sets for Er 3+ and Yb 3+ in the pyrochlores with different chemical compositions were proposed in the literature (see [1,22,23] and references therein). However, the comment written 18 years ago [15], namely, "All are inappropriate as each corresponds to a crystal level scheme and to the ground state wave functions which are not compatible with the experimental data", is actual nowadays as well.…”

Section: Introductionmentioning

confidence: 99%

EPR spectra and magnetization of XY-type rare-earth ions in pyrochlores Y2Ti2O7: RE3+ (RE=Yb, Er)

Batulin¹,

Черосов²,

Gilmutdinov³

et al. 2019

MRSej

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The results of studies of Y 2 Ti 2 O 7 single crystals doped with Er 3+ or Yb 3+ ions by means of electron paramagnetic resonance (EPR) and dc-magnetometry are reported. EPR signals of the trigonal centers with the characteristic hyperfine structure of Er 3+ or Yb 3+ ions were observed. Field dependences of the magnetization of single crystals for magnetic fields directed along the crystallographic axes and temperature dependences of the magnetic susceptibilities were measured. Spin Hamiltonian parameters (g-factors and parameters of the hyperfine interaction) for the Er 3+ and Yb 3+ ions were obtained from the analysis of the experimental data. The registered EPR spectra and magnetization curves are successfully reproduced by simulations in the framework of the crystal-field approach, in particular, with an account for a hybridization of the ground 4f 13 configuration of Yb 3+ ions with the charge transfer states. PACS: 71.70.Ch, 75.10.Dg, 76.30.Kg.

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Experimental Insights into Ground-State Selection of Quantum XY Pyrochlores

Cited by 74 publications

References 143 publications

Effect of chemical pressure on the crystal electric field states of erbium pyrochlore magnets

Effect of chemical pressure on the crystal electric field states of erbium pyrochlore magnets

Competing orders in pyrochlore magnets from a Z2 spin liquid perspective

EPR spectra and magnetization of XY-type rare-earth ions in pyrochlores Y2Ti2O7: RE3+ (RE=Yb, Er)

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