Anomalous resistivity upturn in the van der Waals ferromagnet Fe5GeTe2

Abstract

Fe nGeTe2 ( n = 3, 4, and 5) has recently attracted increasing attention due to its two-dimensional van der Waals characteristic and high temperature ferromagnetism, which makes promises for spintronic devices. A Fe(1) split site is an important structural characteristic of Fe5GeTe2, which makes it very different from other Fe nGeTe2 ( n = 3 and 4) systems. The local atomic disorder and short-range order can be induced by the split site. In this work, high-quality van der Waals ferromagnet Fe5GeTe2 single crystals were grown to study low-temperature transport properties. We found a resistivity upturn below 10 K. The temperature and magnetic field dependence of the resistivity are in good agreement with a combination of the theory of disorder-enhanced three-dimensional electron–electron and single-channel Kondo effect. The Kondo effect exists only at low magnetic fields [Formula: see text], while electron–electron interaction dominates the appearance for the low-temperature resistivity upturn. We believe that the enhanced three-dimensional electron–electron interaction in this system is induced by the local atomic structural disorder due to the split site of Fe(1). Our results indicate that the split site of Fe plays an important role for the exceptional transport properties.

Antisymmetric Peaks Observed in the Hall Resistance of Fe5GeTe2 Ferromagnets: Implications for Spintronic Devices

“…Figures e,f shows the hysteresis loops of Fe 5 GeTe 2 at different temperatures, illustrating that Fe 5 GeTe 2 displays a high magnetization and an exceptionally low coercive field in both the crystallographic c -axis (H// c ) and the ab -plane (H// ab ) orientations. These results suggest a soft ferromagnetic behavior of Fe 5 GeTe 2 , which is consistent with the findings reported by Lv et al Compared to the H// c direction, the lower coercive field for the H// ab plane distinctly demonstrates the strong magnetic crystal anisotropy in Fe 5 GeTe 2 with the easy axis along the ab plane. , …”

“…It can be clearly seen that the magnetization intensity of perpendicular c -axis is significantly greater than that of the parallel c -axis. The anisotropy character of Fe 5 GeTe 2 , along with the easy axis being perpendicular to the c -axis, is confirmed by the difference in the magnetization magnitude for the out-of-plane and in-plane directions. Figures e,f shows the hysteresis loops of Fe 5 GeTe 2 at different temperatures, illustrating that Fe 5 GeTe 2 displays a high magnetization and an exceptionally low coercive field in both the crystallographic c -axis (H// c ) and the ab -plane (H// ab ) orientations.…”

“…Figure a shows the temperature-dependent resistance of Fe 5 GeTe 2 at the zero magnetic field. The resistance diminishes upon cooling, indicating the metallic nature of the Fe 5 GeTe 2 flake. , The inset of Figure a is the optical photographs of Fe 5 GeTe 2 flake device, where the green and black dotted line regions correspond to BN and Fe 5 GeTe 2 , respectively. Figure b shows the magnetoresistance curve of Fe 5 GeTe 2 at 200 K, while the magnetic field is rotating gradually in the ac plane.…”

“…These results suggest a soft ferromagnetic behavior of Fe 5 GeTe 2 , which is consistent with the findings reported by Lv et al 24 Compared to the H//c direction, the lower coercive field for the H//ab plane distinctly demonstrates the strong magnetic crystal anisotropy in Fe 5 GeTe 2 with the easy axis along the ab plane. 22,25 Figure 2a shows the temperature-dependent resistance of Fe 5 GeTe 2 at the zero magnetic field. The resistance diminishes upon cooling, indicating the metallic nature of the Fe 5 GeTe 2 flake.…”

Light-driven Electrodynamics and Demagnetization in FenGeTe2 (n = 3, 5) Thin Films

“…From an electrodynamical perspective, both systems are strongly correlated ferromagnetic metals, where quantum fluctuation effects are crucial for a correct description of the ground state 37 . For instance, Kondo physics at low temperatures has been clearly found in F3GT and recently similar effects have been observed in F5GT 38 . Deviations from the itinerant Stoner model are more prominent in F3GT 39,40 , where local mag-2 netic moments play a crucial role at low temperatures, establishing a Kondo-Ising scenario 41,42 , mediated by an incoherent-coherent crossover (T ∼ 100K) where the 3d conduction electrons hybridize with the local moments 43,44 .…”