Understanding paramagnetic spin correlations in the spin-liquid pyrochloreTb2Ti2O

Abstract

Recent elastic and inelastic neutron scattering studies of the highly frustrated pyrochlore antiferromagnet Tb 2 Ti 2 O 7 have shown some very intriguing features that cannot be modeled by the local ͗111͘ classical Ising model, naively expected to describe this system at low temperatures. By including single-ion excitations from the ground state doublet to higher crystal field levels, we successfully describe the elastic neutron scattering pattern and dispersion relations in Tb 2 Ti 2 O 7 , quantitatively consistent with experimental observations.

The Spin Liquid State of the Tb2Ti2O7 Pyrochlore Antiferromagnet: A Puzzling State of Affairs

“…Note, the PM S(q) is measured at 9K in Gardner et al [19] but at 0.4K in Yasui et al [20] A relaxation of the 111 spin anisotropy in a long-range dipolar AFM pyrochlore model does yield good agreement with the PM S(q) in this material for temperatures T > ∼ |θ CW | > ∼ 10K. [21,22] Recent data for Tb 2 Ti 2 O 7 in the low temperature regime suggests the existence of a spin glass like state. Hysteresis is observed in the field cooled and zero field cooled neutron scattering data below 1.5K.…”

“…[19,22] Applying a random phase approximation (RPA) to a model with exchange and long-range dipoles, the fluctuations between the lowest lying crystal field states can be studied, i.e., the 111 Ising limit is recovered when transitions between states |ψ 0 (ground state) and |ψ 1 (first excited state) have a vanishing matrix element, ψ 1 |S ± |ψ 0 = 0. Using |ψ 0 = |M J = ±4 and |ψ 1 = |M J = ±5 >, the RPA [22] gives excellent semi-quantitative agreement with the PM S(q) and the energy dispersion between the low lying magnetic states of the neutron experiments. [19] However, the RPA still predicts an ordered state at T c ≈ 2K.…”

“…Under high pressure, 2 − 8 GPa, the material orders at T c ≈ 2K, [24] but the spin structure is not the Q = 0 all-in all-out structure predicted from a 111 Ising model, [17,22] The Heisenberg AFM on the pyrochlore lattice is defined by the simple Hamiltonian…”

Quadrupole Order in the Frustrated PyrochloreTb2+xTi2−xOTakatsu1, Onoda2, Kittaka3 et al. 2016Phys. Rev. Lett.53158901View full textAdd to dashboardCite

“…interactions between magnetic dipole moments [the first three terms of Eq. (1)] and the perturbation through first excited crystal-field (CF) states [14,32], and by taking another assumption of Jahn-Teller (JT) distortion [28,33]. Under the present postulation, two ground states of off-stoichiometric Tb 2+x Ti 2−x O 7+y samples [34] will possibly be accounted for by the U(1) QSL (x < x c ) and electric quadrupolar (x > x c ) states of Ref.…”

Magnetic correlations in HoxTb2−xTiChang1, Schweika2, Kao3 et al. 2011Phys. Rev. B174140View full textAdd to dashboardCite

“…12 and 14), which can be described by a model including single-ion excitations from the ground-state doublet to higher crystal-field levels. 21 Here we report the studies of the magnetic behaviors of the mixture compounds of spin ice Ho 2 Ti 2 O 7 and spin liquid Tb 2 Ti 2 O 7 . After considering the correlations between Ho 3+ and Tb 3+ , one would naively expect the spin-ice and spin-liquid states to yield either a long-range order or more realistically a spin-glass state at low temperatures.…”