Magneto-optical properties of group-IV ferromagnetic semiconductor Ge1−xFex grown by low-temperature molecular beam epitaxy

Abstract

A new group-IV ferromagnetic semiconductor, Ge 1-x Fe x , was successfully grown by low-temperature molecular beam epitaxy (LT-MBE) without precipitation of ferromagnetic Ge-Fe intermetallic compounds. The ferromagnetism of Ge 1-x Fe x films was investigated by magnetic circular dichroism (MCD). In particular, the influence of the Fe content (F Fe /F Ge =1 -10%) and growth temperature (100, 200 O C) on the ferromagnetism was carefully studied. The MCD measurements revealed that the band structure of the Ge 1-x Fe x films was identical with that of bulk Ge, and that the large spin splitting of the band structure was induced by the incorporation of Fe atoms into the Ge matrix, indicating the existence of s,p-d exchange interactions. The Ge 1-x Fe x films showed ferromagnetic behavior and the ferromagnetic transition temperature linearly increased with increasing the Fe composition. These results indicate that the epitaxially grown Ge 1-x Fe x is an intrinsic ferromagnetic semiconductor.

Epitaxial growth and magnetic properties of a new group‐IV ferromagnetic semiconductor: Ge 1– x Fe x

“…The Ge 1-x Fe x films grown at T S = 100 and 200 °C showed 2-dimensional growth mode and exhibited diamond-type crystal structure with single phase. This result was consistent with our TEM observation [20]. Note that in our previous paper, it was found using TEM and spatially resolved energy dispersive X-ray spectroscopy (EDX) that the 200 °C-grown Ge 1-x Fe x film exhibited diamond-type crystal structure including slightly nonuniform Fe distribution and tiny stacking fault defects in the epitaxial layer.…”

“…Thus, the formation of ferromagnetic precipitates in the film was ruled out. The Curie temperature (T C ) evaluated from the Arrott plots of the MCD hysteresis loops linearly increased with increasing Fe content (x) up to 17.5% [20]. Thus, we concluded that the Ge 1-x Fe x thin films are characterized as an "intrinsic" ferromagnetic semiconductor.…”

Important role of the non-uniform Fe distribution for the ferromagnetism in group-IV-based ferromagnetic semiconductor GeFe

“…3,4,5,6 In this paper, we present the growth temperature (T S ) dependence of T C and the lattice constant of GeFe, that are investigated by magnetic circular dichroism (MCD) and the X-ray diffraction (XRD) measurements.…”

Annealing-induced enhancement of ferromagnetism and nanoparticle formation in the ferromagnetic semiconductorGeFe

“…6 In the case of Ge 1-x Fe x films, we can grow single-crystal films of a diamond type with the non-uniform distribution of Fe atoms without any intermetallic Fe-Ge compounds, which is appropriate for heterostructure applications, but the current problem of GeFe is its low Curie temperature (T C ) which is at the highest 170 K so far. [7][8][9] Recently, however, GeFe quantum dots with a high T C of ~400 K without any observable precipitates have been reported. 10 Thus, if we can grow GeFe quantum dots (or nano-particles) inside a Ge film with a flat surface or interfaces with other layers (or substrates), they are very promising.…”