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.
@article{arxiv.2209.08342,
title = {Room temperature ferromagnetism in intercalated Fe3-xGeTe2 van der Waals magnet},
author = {Hector Iturriaga and Luis M. Martinez and Thuc T. Mai and Mathias Augustin and Angela R. Hight Walker and M. F. Sanad and Sreeprasad. T. Sreenivasan and Y. Liu and Elton J. G. Santos and C. Petrovic and Srinivasa R. Singamaneni},
journal= {arXiv preprint arXiv:2209.08342},
year = {2022}
}