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Absence of long-range order and magnetic anisotropy in the triangular magnet NdMgAl11O19

Sonu Kumar1,2,3,*, Gaël Bastien2, Jan Prokleška2, Mateusz Kempiński3, Wojciech Kempiński4, Karol Załęski5, Andrej Kancko2, Cinthia Antunes Corrêa1, T. Treu6 et al.

P. Gegenwart6, Małgorzata Śliwińska-Bartkowiak3, and Ross H. Colman2,†

  • *Contact author: sonu.kumar@fzu.cz
  • †Contact author: ross.colman@matfyz.cuni.cz
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Phys. Rev. B 114, 134403 – Published 2 September, 2026

DOI: https://doi.org/10.1103/x1rf-xmrd

Abstract

We investigated the rare-earth triangular-lattice antiferromagnet NdMgAl11O19 using single-crystal magnetization (1.8 K ≤T≤ 300 K, μ0H≤7T) and specific-heat measurements down to 45 mK. The dc susceptibility confirms a well-isolated Kramers doublet ground state with pronounced Ising-type anisotropy, with gc≈3.7, gab≈1.45. Curie-Weiss fits yield weak, anisotropic antiferromagnetic exchange, with θc=−0.54K and θab=−0.87K. Heat capacity measurements show no long-range magnetic order down to 40 mK. Instead, Cm/T exhibits a broad maximum near 0.081 K whose magnitude and field evolution are consistent with short-range correlations in an anisotropic triangular lattice. Applied magnetic fields open a Zeeman gap where the specific-heat anomaly follows Δ=gμBμ0H, and M(H,T) is well described by a Brillouin function for a Jeff=12 moment. The field tuning of the low-temperature entropy manifold allows self-cooling from 1.8 K to 53 mK by adiabatic demagnetization from a μ0H=9T field. These results identify NdMgAl11O19 as a nearly ideal weak-exchange triangular magnet with a field-tunable correlated ground state.

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Phys. Rev. B 114, 134403– Published 2 September, 2026
  • Received 13 February 2026
  • Revised 28 July 2026
  • Accepted 17 August 2026
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