Pervasive beyond room-temperature ferromagnetism in a doped van der Waals magnet: Ni doped Fe$_5$GeTe$_2$ with $T_{\text{C}}$ up to 478 K

Abstract

The existence of long range magnetic order in low dimensional magnetic systems, such as the quasi-two-dimensional (2D) van der Waals (vdW) magnets, has attracted intensive studies of new physical phenomena. The vdW FeN GeTe2 (N = 3, 4, 5; FGT) family is exceptional owing to its vast tunability of magnetic properties. Particularly, a ferromagnetic ordering temperature (TC) above room temperature at N = 5 (F5GT) is observed. Here, our study shows that, by nickel (Ni) substitution of iron (Fe) in F5GT, a record high TC = 478(6) K is achieved. Importantly, pervasive, beyond-room-temperature ferromagnetism exists in almost the entire doping range of the phase diagram of Ni-F5GT. We argue that this striking observation in Ni-F5GT can be possibly due to several contributing factors, in which the structural alteration enhanced 3D magnetic couplings might be critical for enhancing the ferromagnetic order.

Magnetic van der Waals materials: Synthesis, structure, magnetism, and their potential applications

“…[192,193] In (Fe 1−x Ni x ) 5 GeTe 2 , the T C and H c increase firstly and then decreases with the Ni substitution for Fe, and a highest T C of 478 K is obtained at x = 0.36. Chen et al [194] attributed [73]). (c) Thickness-temperature magnetic phase diagram of F4GT crystal (reprinted with permission from Ref.…”