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arXiv · 2010.06741

Collective excitations in the tetravalent lanthanide honeycomb antiferromagnet, Na2PrO3

Marcus J. Daum·Arun Ramanathan·Alexander I. Kolesnikov·Stuart A. Calder·Martin Mourigal·Henry S. La Pierre
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Abstract

Thermomagnetic and inelastic neutron scattering measurements on Na2PrO3 are reported. This material is an antiferromagnetic honeycomb magnet based on the tetravalent lanthanide Pr4+ and has been proposed to host dominant antiferromagnetic Kitaev interactions. These measurements reveal magnetic fluctuations in Na2PrO3 below an energy of 2 meV as well as crystal-field excitations around 230 meV. The latter energy is comparable to the scale of the spin-orbit interaction and explains both the very small effective moment of around 1.0 {\mu}B per Pr4+ and the difficulty to uncover any static magnetic scattering below the ordering transition at TN = 4.6 K. By comparing the low-energy magnetic excitations in Na2PrO3 to that of the isostructural spin-only compound, Na2TbO3, a microscopic model of exchange interactions is developed that implicates dominant and surprisingly large Heisenberg exchange interactions J approximately equal to 1.1(1) meV. Although antiferromagnetic Kitaev interactions with K less than or equal to 0.2J cannot be excluded, the inelastic neutron scattering data of Na2PrO3 is best explained with a delta = 1.24(2) easy-axis XXZ exchange anisotropy.

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Marcus J. Daum, Arun Ramanathan, Alexander I. Kolesnikov, Stuart A. Calder, Martin Mourigal, Henry S. La Pierre. 2020-10-13. Collective excitations in the tetravalent lanthanide honeycomb antiferromagnet, Na2PrO3. https://doi.org/10.1103/physrevb.103.l121109

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