Universal Dynamic Magnetism in Yb Pyrochlores with Disparate Ground States

Published

March 14, 2016

Author(s)

A. M. Hallas, J. Gaudet, Nicholas Butch, M. Tachibana, R. S. Freitas, G. M. Lake, C. R. Wiebe, B. D. Gaulin

Abstract

The ytterbium pyrochlore magnets, Yb₂B₂O₇ (B=Sn, Ti, Ge) are well described by S_{eff = 1/2 quantum spins with local XY anisotropy, decorating the cubic pyrochlore lattice and interacting via anisotropic exchange. Structurally, while only the non-magnetic B-site cation, and hence, primarily the lattice parameter, changes across the series, a range of magnetic behaviors are observed. The low temperature magnetism in Yb}d2^Ti₂O₇ and Yb₂Sn₂O₇ has ferromagnetic character, while Yb₂Ge₂O₇ displays an antiferromagnetically ordered Neel state at low temperatures. We present the spin dynamical properties of these three systems using inelastic neutron scattering. While the static properties of the ytterbium pyrochlores are distinct, we find a ubiquitous character to their exotic spin dynamics. All three show a gapless continuum of spin excitations, resembling over-damped ferromagnetic spin waves at low Q. Furthermore, the specific heat of the series also follows a common form with a broad, high-temperature anomaly followed by a sharp low-temperature anomaly only, remaining unchanged across the sharp anomaly. This result suggests that the primary order parameter below T_c or T_N in the ytterbium pyrochlores is associated with multipolar degrees of freedom beyond dipole order.

Citation

Physical Review B

Volume

93

Issue

10

Pub Type

Journals

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Citation

Hallas, A. , Gaudet, J. , Butch, N. , Tachibana, M. , Freitas, R. , Lake, G. , Wiebe, C. and Gaulin, B. (2016), Universal Dynamic Magnetism in Yb Pyrochlores with Disparate Ground States, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920058 (Accessed April 25, 2024)