Thermodynamic properties of quadrupolar states in the frustrated pyrochlore magnet Tb₂Ti₂O₇

Abstract

Abstract. The low-temperature thermodynamic properties of the frustrated pyrochlore Tb 2+xTi2−xO7+y have been studied using the single crystal of x = 0.005 sitting in a long range ordered phase in the x-T phase diagram. We observed that the specific heat exhibits a minimum around 2 K and slightly increases on cooling, similar to a Schottky-like anomaly for canonical spin ices. A clear specific-heat peak observed at T c = 0.53 K is ascribable to the phase transition to a quadrupolar state, which contributes to a relatively large change in entropy, S ≃ 2.7 J K −1 mol −1 . However, it is still smaller than R ln 2 for the ground state doublet of the Tb ions. The entropy release persists to higher temperatures, suggesting strong fluctuations associated with spin ice correlations above T c. We discuss the field dependence of the entropy change for H|| [111] and H|| [001].

Continuum Excitation and Pseudospin Wave in Quantum Spin-Liquid and Quadrupole Ordered States of Tb2+xTi2−xO7+y

“…We think that our samples are self-consistent among Refs. [31][32][33][34][35]40] and the present study. The sample used in Ref.…”

“…The starting material Tb 4 O 7 used in our investigations from 2012, i.e., Refs. [31][32][33][34][35]40] and the preset study, was from a single batch produced by Shin-Etsu Chemical.…”

Magnetoelastic excitation spectrum in the rare-earth pyrochlore Tb2Ti2O7

“…As mentioned, neither of these possibilities occurs, and the exact low-temperature behavior is somewhat obscured by sample-dependent properties such as the presence or absence of a heat capacity anomaly [3,[20][21][22], or different (partial) spin freezing temperatures [21][22][23][24][25]. Such sample dependence in rare-earth pyrochlores is typically attributed to very small levels of off stoichiometry [26], and detailed experimental work on samples in which the exact stoichiometry is varied according to Tb 2+x Ti 2−x O 7+y [3][4][5][27][28][29][30][31][32][33] suggests that for a small range of −0.05 x 0.04, a phase transition that is not of magnetic dipole or structural origin (i.e., a hidden order) appears at T ≈ 0.5 K and everywhere outside this critical compositional range, the spin liquid develops.…”

Crystal field excitations fromYb3+ions at defective sites in highly stuffedYb2Ti2O7Sala1, Maharaj2, Stone3 et al. 2018Phys. Rev. B9030View full textAdd to dashboardCite

“…The possibility that a quantum analogue of the spin ice ground state, i.e. quantum spin ice (QSI), may exist in certain low moment pyrochlore magnets, including Yb 2 Ti 2 O 7 and Pr 2 Zr 2 O 7 , has generated much excitement [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].At low temperatures Yb 2 Ti 2 O 7 displays two magnetic heat capacity anomalies: a broad one near 2 K and a sharp anomaly signifying a thermodynamic phase transition near T C = 0.26 K [25][26][27][28][29]. Below T C , the ordered structure is thought to be a splayed ferromagnet with moments pointing close to the (100) directions [30][31][32][33][34].…”

“…The possibility that a quantum analogue of the spin ice ground state, i.e. quantum spin ice (QSI), may exist in certain low moment pyrochlore magnets, including Yb 2 Ti 2 O 7 and Pr 2 Zr 2 O 7 , has generated much excitement [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”