Tyler Werner, Yale University

Abstract:

Fe5GeTe2 (FGT), a room temperature 2D metallic van der Waals (vdW) ferromagnet, is a promising candidate for industrial spintronic application with excellent thermal stability, highly tunable magnetic ground states, and compatibility with atomic limit device manufacture. Recently, nickel doping of the iron sites in FGT was found to increase the Curie Temperature (TC) from ~270K to over 470K, a record high TC for vdW magnets [1]. However, the TC enhancement of over 200K is a mystery as nickel is known to be a nonmagnetic dilutant of the magnetic moment. Here, using angle resolved photoemission spectroscopy (ARPES), we report a correlation between the chemical potential and TC across all nickel doping levels. Combining ARPES with X-Ray diffraction (XRD) and core level X-Ray photoemission spectroscopy (XPS), we find a surprising anticorrelation between the coherence of the electronic bands with the underlying lattice structure. Using spin-resolved ARPES and resonant ARPES at Fe/Ni-L3 edge, we find that local iron states contribute most to the magnetic moments. We propose that nickel doping enhances TC by binding the local iron moments with an itinerant electron-mediated exchange interaction at exceptionally long range, which persists even after the appearance of mesoscopic nonmagnetic nickel domains. 

[1] Xiang Chen et al. “Pervasive beyond Room-Temperature Ferromagnetism in a Doped van der Waals Magnet.” Physical Review Letters 128, 217203 (2022). 

[2] Tyler L. Werner et al., in preparation

Poster Session Link: https://gather.town/invite?token=0pEoq7VP

If you have any questions for the presenter, please contact them via email: tyler.werner@yale.edu