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arXiv · 2602.08361

Direct Evidence of a Near-Ideal Jeff = 1/2 Ground State in Triangular-Lattice Na2BaCo(PO4)2

M. M. Ferreira-Carvalho·S. H. Chen·Y. C. Ku·Anagha Jose·Ryan Morrow·C. Y. Kuo·C. F. Chang·Z. Hu·M. W. Haverkort·L. H. Tjeng
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Abstract

We investigated the local Co 3d electronic structure of Na2BaCo(PO4)2 using polarization-dependent X-ray absorption spectroscopy (XAS) in combination with full multiplet cluster calculations. We employed the line-fitting inverse partial fluorescence yield (IPFY) technique to obtain accurate XAS spectra from strong insulating materials. Our combined experimental and theoretical analysis reveals a very small effective trigonal distortion of only 11 meV in the CoO6 octahedra, indicating a close to ideal condition to render a ground state with the Jeff = 1/2 character. With our cluster model we were also able to simulate magnetic susceptibility measurements along different directions in the crystal. These findings highlight Na2BaCo(PO4)2 as a promising platform for exploring exotic magnetic phenomena associated with Jeff = 1/2 ground states on triangular lattices.

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M. M. Ferreira-Carvalho, S. H. Chen, Y. C. Ku, Anagha Jose, Ryan Morrow, C. Y. Kuo, C. F. Chang, Z. Hu, M. W. Haverkort, L. H. Tjeng. 2026-02-09. Direct Evidence of a Near-Ideal Jeff = 1/2 Ground State in Triangular-Lattice Na2BaCo(PO4)2. https://doi.org/10.1103/65bn-63kj

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