Antiferroquadrupolar correlations in the quantum spin ice candidatePr2Zr2O7

Abstract

(2016) Antiferroquadrupolar correlations in the quantum spin ice candidate Pr2Zr2O7. Physical Review B, 94 (16). 165153 Permanent WRAP URL: http://wrap.warwick.ac.uk/87826 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher statement: © 2016 American Physical Society A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. We present an experimental study of the quantum spin ice candidate pyrochlore compound Pr 2 Zr 2 O 7 by means of magnetization measurements, specific heat, and neutron scattering up to 12 T and down to 60 mK. When the field is applied along the [111] and [110] directions, k = 0 field-induced structures settle in. We find that the ordered moment rises slowly, even at very low temperature, in agreement with macroscopic magnetization. Interestingly, for H [110], the ordered moment appears on the so-called α chains only. The spin excitation spectrum is essentially inelastic and consists in a broad flat mode centered at about 0.4 meV with a magnetic structure factor which resembles the spin ice pattern. For H [110] (at least up to 2.5 T), we find that a well-defined mode forms from this broad response, whose energy increases with H , in the same way as the temperature of the specific-heat anomaly. We finally discuss these results in the light of mean field calculations and propose an interpretation where quadrupolar interactions play a major role, overcoming the magnetic exchange. In this picture, the spin ice pattern appears shifted up to finite energy because of those interactions. We then propose a range of acceptable parameters for Pr 2 Zr 2 O 7 that allow to reproduce several experimental features observed under field. With these parameters, the actual ground state of this material would be an antiferroquadrupolar liquid with spin-ice-like excitations.

Single crystal growth, structure and magnetic properties of Pr2Hf2O7pyrochlore

“…The calculated values of the CurieWeiss temperature θ W , and of the effective moment µ eff are in agreement with those determined by detailed investigations of the low temperature magnetic properties of our Pr 2 Hf 2 O 7 crystals [57]. We note the apparent discrepancy between the negative CurieWeiss temperature and the fact that the physics of Pr-based pyrochlores appears to be related to spin ice [27,57,59]. However, it has recently been established using inelastic neutron spectroscopy [59] that, in Pr 2 Zr 2 O 7 , the parameters of the Hamiltonian for Prbased pyrochlores [25] lead to a phase where quadrupolar correlations can overcome the antiferromagnetic exchange and account for the spin ice-like structure factor.…”

“…We note the apparent discrepancy between the negative CurieWeiss temperature and the fact that the physics of Pr-based pyrochlores appears to be related to spin ice [27,57,59]. However, it has recently been established using inelastic neutron spectroscopy [59] that, in Pr 2 Zr 2 O 7 , the parameters of the Hamiltonian for Prbased pyrochlores [25] lead to a phase where quadrupolar correlations can overcome the antiferromagnetic exchange and account for the spin ice-like structure factor. The magnetization measured along the three directions as a function of applied magnetic field M (H) at various temperatures is shown in Fig.…”

Magnetic properties and crystal field inPr2Zr2O7

“…We note also that such a term would naturally appear, at the mean-field level, in the context of quadrupole-quadrupole interactions. In that case, B 2 2 would model the quadrupolar mean field experienced by a given ion [15,28].…”

“…Their thermal variation suggests that the strength of the antiferromagnetic effective exchange interaction strongly decreases between high (∼300 K) and low (T < 20 K) temperature. We finally compute the M(H ) profiles and compare them to recent available single-crystal magnetic measurements [15]. To account qualitatively for the experiments, especially the absence of quick saturation of the magnetization at very low temperature, the influence of crystal-field imperfections breaking the local trigonal symmetry is discussed.…”

Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice inPr2Zr2O7

“…After completion of our work, we became aware of an independent work by Petit et al on the same compound, which suggests transverse interactions could be important in PZO. [22] …”