Experimental Evidence for Field-Induced Emergent Clock Anisotropies in the XY Pyrochlore Er2Ti2O7

Published

February 6, 2017

Author(s)

Jonathan Gaudet, A. M. Hallas, J. Thibault, Nicholas Butch, H. A. Dabkowska, B. D. Gaulin

Abstract

The XY pyrochlore antiferromagnet Er₂Ti₂O₇ exhibits a rare case of Z₆ discrete symmetry breaking in its ψ₂ magnetic ground state. The Ising model, with Z₂ symmetry breaking, is known to capture the salient physics of many magnetic materials and a wealth of other physical systems. Despite being well-studied theoretically, systems with higher discrete symmetry breakings are uncommon in nature. Thus, Er₂Ti₂O₇ provides a remarkable experimental playground for the study of broken Z_n symmetry, for n>2. In particular, recent theoretical work probed Zeeman coupling on a pyrochlore lattice with broken Z₆ symmetry and applied it to Er^2^Ti₂O₇. Multiple domain transitions are predicted to occur, depending on the crystallographic orientation of the magnetic field, inducing rich and controllable magnetothermodynamic behavior. In this work, we perform neutron scattering measurements on Er₂Ti₂O₇ with a magnetic field applied along the [001] and [111] directions, providing the first experimental observation of these exotic domain transitions. In a [001] field, a ψ₂ to ψ₃ transition is observed at a critical field of 0.18 ± 0.05 T. We are thus able to extend the concept of the spin-flop transition, which have long been observed in Ising systems, to higher discrete Z_N symmetry systems. In a [111] field, we observe a series of successive domain-based phase transitions for fields of 0.15 ± 0.03 T. We show that these field-induced transitions are consistent with the emergence of two-fold, three-fold and possibly six-fold Zeeman terms. Considering all the possible ψ₂ and ψ_{3 domains, these Zeeman terms can be mapped onto a conventional clock - exemplifying a literal clock anisotropy. Lastly, characterizing the domain selection in Er}d2^Ti₂O₇ provides a pathway for determining the strength of order-by-disorder as the ground state selection mechanism.

Citation

Physical Review B

Volume

95

Issue

5

Pub Type

Journals

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Keywords

magnetism

Citation

Gaudet, J. , Hallas, A. , Thibault, J. , Butch, N. , Dabkowska, H. and Gaulin, B. (2017), Experimental Evidence for Field-Induced Emergent Clock Anisotropies in the XY Pyrochlore Er₂Ti₂O₇, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922730 (Accessed April 26, 2024)