Temperature and Magnetic Field Dependence of Spin-Ice Correlations in the Pyrochlore Magnet Tb^2^Ti2O7

Published

July 23, 2014

Author(s)

K. Fritsch, E. Kermarrec, Kathryn Aileen Ross, Yiming Qiu, John R. Copley, D. Pomaranski, J. B. Kycia, H. A. Dabkowska, B. D. Gaulin

Abstract

We present a parametric study of the diffuse magnetic scattering at (1/2, 1/2, 1/2}) positions in reciprocal space, ascribed to a frozen antiferromagnetic spin ice state in single crystalline Tb₂Ti₂O₇. Our high-resolution neturon scattering measurements show that the elastic (-0.02 meV < E < 0.02 meV) (1/2,1/2,1/2)} scattering develops strongly below 275 mK, and correlates with the opening of a spin gap of 0.06-0.08 meV over most of the Brillouin zone. The concomitant low-lying magnetic spin excitations are weakly dispersive and appear to soften near the (1/2,1/2,1/2}) wave vector at 80 mK. The nature of the transition at 275 mK has many characteristics of spin glass behavior, consistent with ac-susceptibility measurements. The application of a magnetic field of 0.075 T applied along the [1-10] direction destroys the (1/2,1/2,1/2}) elastic scattering, revealing the fragility of this short-range ordered ground state. We construct a refined H-T phase diagram for Tb₂Ti₂O₇ and [1-10] fields which incorporates this frozen spin ice regime and the antiferromagnetic long-range order previously known to be induced in relatively large fields. Specific heat measurements on the same crystal reveal a sharp anomaly at T_c 450 mK and no indication of a transition near 275 mK. We conclude that the higher temperature specific heat peak is not related to the magnetic ordering but is likely a signal of other, nonmagnetic, correlations.

Citation

Physical Review B

Volume

90

Issue

1

Pub Type

Journals

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Keywords

frustration, spin ice, pyrochlore, spin liquid, magnetism

Citation

Fritsch, K. , Kermarrec, E. , Ross, K. , Qiu, Y. , Copley, J. , Pomaranski, D. , Kycia, J. , Dabkowska, H. and Gaulin, B. (2014), Temperature and Magnetic Field Dependence of Spin-Ice Correlations in the Pyrochlore Magnet Tb^2^Ti₂O₇, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915187 (Accessed April 23, 2024)