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arXiv · 2103.02391

Electric Quadrupolar Contributions in the Magnetic Phases of UNi$_4$B

T. Yanagisawa·H. Matsumori·H. Saito·H. Hidaka·H. Amitsuka·S. Nakamura·S. Awaji·D. I. Gorbunov·S. Zherlitsyn·J. Wosnitza·K. Uhlířová·M. Vališka·V. Sechovský
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Abstract

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi$_4$B. The transverse ultrasonic mode $C_{66}$ shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to $\sim0.33$ K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that $\Gamma_6$(E$_{\rm 2g}$) electric quadrupolar degrees of freedom in localized $5f^2$ ($J = 4$) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi$_4$B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

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T. Yanagisawa, H. Matsumori, H. Saito, H. Hidaka, H. Amitsuka, S. Nakamura, S. Awaji, D. I. Gorbunov, S. Zherlitsyn, J. Wosnitza, K. Uhlířová, M. Vališka, V. Sechovský. 2021-03-03. Electric Quadrupolar Contributions in the Magnetic Phases of UNi$_4$B. https://doi.org/10.1103/physrevlett.126.157201

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