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  • Letter
  • Open Access

Dielectric signatures of crystal-field and low-temperature correlated dynamics in NdMgAl11O19

Sonu Kumar1,2,3,*, Gaël Bastien2, Maxim Savinov1, Małgorzata Śliwińska-Bartkowiak3, Ross H. Colman2, and Stanislav Kamba1,†

  • *Contact author: sonuwhf@gmail.com
  • †Contact author: kamba@fzu.cz
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Phys. Rev. B 114, L111103 – Published 10 August, 2026

DOI: https://doi.org/10.1103/g44t-yhsk

Abstract

We report dielectric spectroscopy of single-crystalline NdMgAl11O19, a magnetoplumbite hexaaluminate in which localized Nd3+ moments coexist with a polarizable AlO5 bipyramidal network. The real part of the permittivity ɛc′(T), measured along the crystallographic c axis, increases as the temperature is lowered from 275 K to 30 K and is frequency-independent between 4 Hz and 50 kHz. At lower temperatures, a frequency-dependent decrease in permittivity is observed, followed by a further upturn below 2 K. The high-frequency ɛc′(T) is described by a Barrett formula supplemented by an effective two-level contribution, yielding a robust gap of Δ=25.9(3)K consistent with the lowest Nd3+ crystal-electric-field (CEF) splitting. Below ∼30K, the dielectric response becomes strongly frequency and magnetic-field dependent. Isothermal ɛc′(H) measurements reveal a reproducible low-field crossover near μ0Hc≃0.85T, which we attribute to the competition between antiferromagnetic correlations and Zeeman splitting of the ground-state Kramers doublet. NdMgAl11O19 thus provides a Kramers reference system in which dielectric signatures of the excited-state CEF manifold can be distinguished from those of the field-tuned, correlation-dominated ground-state doublet in the centrosymmetric frustrated magnetoplumbite host.

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Outline

Information

Phys. Rev. B 114, L111103– Published 10 August, 2026
  • Received 27 April 2026
  • Revised 22 June 2026
  • Accepted 21 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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