Alloying magnetic metals in “2D”: from old wisdom to new physics

Speaker: Dr. Yu He
Affiliation: Yale University
Date: September 18, 2026

Abstract:

Transition metal chalcogenide is a key host for van der Waals (vdW) magnets, many of which maintain magnetism down to the thin layer limit. Recent discovery of tunable ferromagnetism between 50-500K in vdW (Fe,Ni)5GeTe2 raised the question of how this is achieved, and how they differ (if at all) from elemental magnetic thin films. Motivated by the uncanny resemblance between the (Ni,Fe)5GeTe2 and Ni-Fe alloy phase diagrams, we combine spin- and angle-resolved photoemission spectroscopy with operando synchrotron x-ray diffraction, and show that such group VIII element-rich "high-Tc" vdW magnets can to some extent be considered "atomically encapsulated" magnetic alloys. However, their distinct magnetic site-selectivity, cross vdW gap interaction, and mesoscopic strain enable unique flexibility behind the robust magnetism. I will also discuss our recent effort to introduce magnetic fields into photoemission sample environments via magnetic metamaterial hetero-integration, paving way for in situ controlled magnetic material investigations.
[1] Werner, in preparation
[2] Li, J Phys Chem Lett 16, 12947 (2025)