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arXiv · 2610.17315

Evidence of an anisotropic Griffiths phase in a two-dimensional van der Waals magnet

Anupam K. Singh·Dhananjay Nair·Holger Meyerheim·Stuart S. P. Parkin·Banabir Pal
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Abstract

Over the last decade, the emerging field of two-dimensional van der Waals magnetism has focused mainly on long-range-ordered magnetic phases. Disordered magnetic phases, however, remain largely unexplored. Here, we report a highly anisotropic Griffiths phase driven by self-intercalation in the van der Waals magnet Fe5GeTe2. We find evidence of short-range-ordered ferromagnetic clusters embedded in a paramagnetic matrix, which dominate the magnetic response between the Curie temperature and a higher characteristic Griffiths temperature. An anomalous power-law divergence in the magnetic susceptibility, universal Lee Yang scaling, and distinct entropy anomalies provide further evidence for this phase. Strikingly, the non-analytic Griffiths response emerges exclusively under in-plane magnetic fields, whereas out-of-plane fields abruptly alter this behavior. This directional dependence indicates that the local magnetic interactions within nanoscale clusters are closely coupled to the layered lattice geometry. Our findings establish a regime of dimensionally constrained, disorder-driven magnetism and identify self-intercalated van der Waals magnets as a platform for investigating the interplay between magnetic disorder, anisotropy, and reduced dimensionality.

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Anupam K. Singh, Dhananjay Nair, Holger Meyerheim, Stuart S. P. Parkin, Banabir Pal. 2026-10-12. Evidence of an anisotropic Griffiths phase in a two-dimensional van der Waals magnet. https://arxiv.org/abs/2610.17315

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