Room temperature ferromagnetism in intercalated Fe3-xGeTe2 van der Waals magnet

TL;DR

This study demonstrates that electrochemical intercalation of TBA+ ions into Fe3-xGeTe2 induces a stable room-temperature ferromagnetic phase, significantly increasing the Curie temperature and offering a practical approach to high-temperature 2D magnetic materials.

Contribution

The paper reports the discovery of room-temperature ferromagnetism in Fe3-xGeTe2 induced by TBA+ intercalation, a novel and effective method for enhancing magnetic properties in vdW magnets.

Findings

Curie temperature increased to 350 K after intercalation

Intercalation leads to stable and chemically robust ferromagnetic phase

Charge transfer from intercalation likely causes the observed ferromagnetism

Abstract

Among several well-known transition metal-based compounds, the van der Waals (vdW) Fe3-xGeTe2 (FGT) magnet is a strong candidate for use in two-dimensional (2D) magnetic devices due to its strong perpendicular magnetic anisotropy, sizeable Curie temperature (TC ~ 154 K), and versatile magnetic character that is retained in the low-dimensional limit. While the TC remains far too low for practical applications, there has been a successful push toward improving it via external driving forces such as pressure, irradiation, and doping. Here we present experimental evidence of a novel room-temperature (RT) ferromagnetic phase induced by the electrochemical intercalation of common tetrabutylammonium cations (TBA+) into FGT bulk crystals. We obtained Curie temperatures as high as 350 K with chemical and physical stability of the intercalated compound. The temperature-dependent Raman measurements in combination with vdW-corrected ab initio calculations suggest that charge transfer (electron doping) upon intercalation could lead to the observation of RT ferromagnetism. This work demonstrates that molecular intercalation is a viable route in realizing high-temperature vdW magnets in an inexpensive and reliable manner.