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Universal Dynamic Magnetism in Yb Pyrochlores with Disparate Ground States



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


The ytterbium pyrochlore magnets, Yb2B2O7 (B=Sn, Ti, Ge) are well described by Seff = 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 Ybd2^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 Tc or TN in the ytterbium pyrochlores is associated with multipolar degrees of freedom beyond dipole order.
Physical Review B


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], (Accessed May 26, 2024)


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Created March 13, 2016, Updated October 12, 2021