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arXiv · 2601.22078

Inverted anisotropy of the partially screened magnetic impurity

Krzysztof P. Wójcik·Michał P. Kwasigroch
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Abstract

We investigate a single magnetic impurity in the presence of strong spin-orbit coupling and single-ion anisotropy. We show that at sufficiently strong coupling there exists a finite temperature window, before the moment is completely screened, where the magnetic anisotropy of the system flips: the hard-axis becomes the easy-axis or vice versa. We derive this rigorously for a single impurity using numerical renormalization group calculations as well as Nozieres' strong-coupling limit and discuss its relevance to heavy-fermion compounds which order magnetically along the hard-direction. We show that the coexistence of Curie-like response and Kondo fluctuations is stabilized along the initially hard direction leading to the anisotropy switch.

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Krzysztof P. Wójcik, Michał P. Kwasigroch. 2026-01-29. Inverted anisotropy of the partially screened magnetic impurity. https://arxiv.org/abs/2601.22078

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