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arXiv · 1409.6907

Ultrasonic investigations of spin-ices Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ in and out of equilibrium

S. Erfanifam·S. Zherlitsyn·S. Yasin·Y. Skourski·J. Wosnitza·A. A. Zvyagin·P. McClarty·R. Moessner·G. Balakrishnan·O. A. Petrenko
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Abstract

We report ultrasound studies of spin-lattice and single-ion effects in the spin-ice materials Dy$_2$Ti$_2$O$_7$ (DTO) and Ho$_2$Ti$_2$O$_7$ (HTO) across a broad field range up to 60 T, covering phase transformations, interactions with low-energy magnetic excitations, as well as single-ion effects. In particular, a sharp dip observed in the sound attenuation in DTO at the gas-liquid transition of the magnetic monopoles is explained based on an approach involving negative relaxation processes. Furthermore, quasi-periodic peaks in the acoustic properties of DTO due to non-equilibrium processes are found to be strongly affected by {\em macroscopic} thermal-coupling conditions: the thermal runaway observed in previous studies in DTO can be suppressed altogether by immersing the sample in liquid helium. Crystal-electric-field effects having higher energy scale lead to a renormalization of the sound velocity and sound attenuation at very high magnetic fields. We analyze our observations using an approach based on an analysis of exchange-striction couplings and single-ion effects.

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S. Erfanifam, S. Zherlitsyn, S. Yasin, Y. Skourski, J. Wosnitza, A. A. Zvyagin, P. McClarty, R. Moessner, G. Balakrishnan, O. A. Petrenko. 2014-09-24. Ultrasonic investigations of spin-ices Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ in and out of equilibrium. https://doi.org/10.1103/physrevb.90.064409

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