Room Temperature Ferromagnetic, Anisotropic, Germanium Rich FeGe(001) Alloys

Abstract

Ferromagnetic FexGe1−x with x = 2%–9% are obtained by Fe deposition onto Ge(001) at high temperatures (500 °C). Low energy electron diffraction (LEED) investigation evidenced the preservation of the (1 × 1) surface structure of Ge(001) with Fe deposition. X-ray photoelectron spectroscopy (XPS) at Ge 3d and Fe 2p core levels evidenced strong Fe diffusion into the Ge substrate and formation of Ge-rich compounds, from FeGe3 to approximately FeGe2, depending on the amount of Fe deposited. Room temperature magneto-optical Kerr effect (MOKE) evidenced ferromagnetic ordering at room temperature, with about 0.1 Bohr magnetons per Fe atom, and also a clear uniaxial magnetic anisotropy with the in-plane [110] easy magnetization axis. This compound is a good candidate for promising applications in the field of semiconductor spintronics.

Room Temperature Ferromagnetic Mn:Ge(001)

“…In the case of high temperature deposition of Fe on Si(001) (2 × 1)−(1 × 2) by using exactly the same setup, the LEED pattern vanishes starting with 1 nm of Fe thickness [20,21]; in the case of Sm/Si(001), a broad LEED pattern subsisted up to about 3.5 nm of Sm deposited [22,23]. A case closer to the present one was presented by Fe deposited in Ge(001) by keeping the substrate at high temperature (500 °C) [24], where the (1 × 1) LEED pattern of Ge(001) subsisted after 2 nm of Fe deposited; however, without providing also the (2 × 1)−(1 × 2) surface reconstruction of Ge(001). By taking into account all of the previous experiments, we can say that the observation of a Ge(001) surface quite similar to clean Ge(001), after a high amount of Mn deposited, is a new result.…”

“…in a vacuum kept in the low 10 −9 mbar range) [24,26,27]. Clear (2 × 1)–(1 × 2) LEED were obtained, as seen in Figure 1.…”

“…The system is described in greater detail in references [22,24]. The base pressure in all ultrahigh vacuum (UHV) chambers is in the low 10 −10 mbar to 10 −11 vacuum range.…”

Thermal evolution of Fe on Ge(1 1 1)–c(2 × 8) surface and the effect of (3×3)R30° Ag–Ge buffer layer

“…Fe-Si-base alloys have been widely and tenaciously investigated [11][12][13]. Although Fe-Si and Fe-Ge alloy structures are similar, Fe/Ge alloys exhibit certain unique properties, such as the helimagnetic property of B20 FeGe films [14] used in skyrmion devices without FeSi films; moreover, the magnetic coercivity of Fe/Ge(1 0 0) is larger than that of Fe/Si(1 0 0) [15]. Furthermore, Fe-Ge alloys with bulk and thin films differ in properties such as anisotropic direction [14][15][16][17] and antiferromagnetism [16].…”

“…Furthermore, Fe-Ge alloys with bulk and thin films differ in properties such as anisotropic direction [14][15][16][17] and antiferromagnetism [16]. In addition, Fe/Ge(1 0 0) films exhibit exchange bias [15]. By varying surface temperature, the rich behavior of Fe/Ge interfaces with complex alloy phases [18], such as intermixing, defect, and diffusion [17], changes the surface morphology to form FeGe x surface alloy structures corresponding to the magnetic properties.…”