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arXiv · 2511.12355

Crystal-Field--Driven Magnetoelectric Coupling in the Non-Kramers Hexaaluminate PrMgAl11O19

Sonu Kumar·Gaël Bastien·Ross H. Colman·Maxim Savinov·Petr Proschek·Michal Vališka·Mateusz Kempiński·Wojciech Kempiński·Małgorzata Śliwińska-Bartkowiak·Stanislav Kamba
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Abstract

We report broadband dielectric spectra of the non-Kramers hexaaluminate PrMgAl\textsubscript{11}O\textsubscript{19}, revealing a pronounced interplay between permittivity and magnetization at cryogenic temperatures. The zero-field dielectric response follows a Barrett-type quantum-paraelectric form, while a broad dielectric anomaly near \SI{5}{K} shows a complex field dependence that mirrors the multi-hump behavior of the magnetic specific heat, evidencing robust magnetoelectric coupling. The inverse permittivity $\varepsilon'^{-1}(T,H)$ scales linearly with $M^2$, consistent with a biquadratic $P^2M^2$ term in a Landau framework. Fits yield temperature-dependent coupling constant $\lambda(T)$ that decreases with heating from ($1.07\pm0.01)\times10^{-4}\,\mu_{\mathrm{B}}^{-2}$ (at 5\,K) to $(4.77\pm0.02)\times10^{-5}\,\mu_{\mathrm{B}}^{-2}$ (at 10\,K), reflecting the thermal population of low-lying energy levels of Pr$^{3+}$. Consistently, the uniaxial thermal expansion develops an additional low-temperature hump below $\sim\SI{30}{K}$ that is progressively suppressed by magnetic field, recovering an approximately saturated response by \SI{9}{T}. These results identify PrMgAl\textsubscript{11}O\textsubscript{19} as a paradigmatic non-Kramers hexaaluminate where quantum paraelectricity and magnetoelectric interactions are intrinsically entangled, establishing hexaaluminates as a tunable platform for magnetoelectric physics in frustrated quantum materials.

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Sonu Kumar, Gaël Bastien, Ross H. Colman, Maxim Savinov, Petr Proschek, Michal Vališka, Mateusz Kempiński, Wojciech Kempiński, Małgorzata Śliwińska-Bartkowiak, Stanislav Kamba. 2025-11-15. Crystal-Field--Driven Magnetoelectric Coupling in the Non-Kramers Hexaaluminate PrMgAl11O19. https://doi.org/10.1016/j.jallcom.2026.187535

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