Thermodynamic and magnetic properties of rare-earth delafossites and the example of NaGdS₂

Abstract:

Rare-earth delafossites have a crystal structure containing ideal triangular magnetic planes, which form a triangular lattice magnet. These layers are characterised by magnetic frustration or non-trivial magnetic order states. Rare-earth delafossites are promising candidates for a QSL ground state, and may find interesting applications in computing due to low-energy spinon excitations.

In recent years, special efforts have been made with S=½ delafossites of the type ARX₂ (A=alkali metal; R=rare earth; X=S, Se) to find an ideal S=½ QSL. In this talk KCeS₂ [1,2] and NaYbS₂ [3,4] are considered more extensively. For both compounds a transition in the mK range was found. The differences in the measurments will be presented and discussed.

A number of new measurments were made on NaGdS₂ single crystals. This delafossite with magnetic Gd³⁺ ions, which has been extensively investigated for the first time, is of special interest due to the pure spin moment J=S=7/2. Thermodynamic and magnetic properties could be investigated by measurements of thermal expansion / magnetisation, magnetostriction and specific heat. These first results form the basis of the discussion. Despite the application of these macroscopic measurment methods on very small samples (~µm), essential physical data could be extracted. The new results and their comparison to other samples will be the main part of this presentation.

[1] G. Bastien et al., SciPost Phys. 9, 041 (2020)

[2] A. Kulbakov et al., J. Phys.: Condens. Mat. 33, 425802 (2021)

[3] M. Baenitz et al., Phys Rev B 98, 220409(R) (2018)

[4] R. Sarkar et al., Phys. Rev. B 100, 241116(R) (2019)

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