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Low-temperature magnetism and crystal field effects in the triangular-lattice delafossites TlErSe2 and TlTmSe2

Bastian Rubrecht1, Ellen Häußler2, Mirtha Pillaca2, Pritam Bhattacharyya3, Liviu Hozoi3, Artem Nosenko1,4, Dmitri V. Efremov1, Bernd Büchner1,5, Anja U. B. Wolter1 et al.

Thomas Doert2

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Phys. Rev. B 114, 264404 – Published 3 November, 2026

DOI: https://doi.org/10.1103/sfns-yxpr

Abstract

Delafossite compounds containing rare-earth ions have been proven to be an ideal platform to investigate frustrated magnetic ground states. Here, we discuss two triangular-lattice antiferromagnets, TlErSe2 and TlTmSe2, as potential candidates for hosting exotic quantum states. Powder x-ray diffraction data analysis of the black polycrystalline TlMSe2 (M: Er and Tm) samples confirms the phase purity. Both materials crystallize in the trigonal α−NaFeO2 structure (R3¯m) with lattice parameters a=4.1070(4)Å and c=23.1472(1)Å for the erbium compound and a=4.0916(1)Å and c=23.1483(2)Å for the thulium compound. Magnetic susceptibility measurements show an effective moment of μeff=9.6(2)μB/f.u. (7.5(1)μB/f.u.) for TlErSe2 (TlTmSe2) for temperatures above 200 K. While He3 specific heat measurements reveal long-range magnetic order below TN=0.42K for TlErSe2, no sign of long-range magnetic order was observed for TlTmSe2. Combining both experimental and computational results, we discuss the striking difference in the magnetic behavior of TlTmSe2 and map out the T−H phase diagram for polycrystalline TlErSe2.

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Phys. Rev. B 114, 264404– Published 3 November, 2026
  • Received 15 December 2025
  • Revised 13 August 2026
  • Accepted 25 August 2026
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