Epitaxial Fe3Si films on GaAs(100) substrates by means of electron beam evaporation.

This paper presents results on the preparation, structural, electrical and magnetic properties of Fe(3)Si films as a representative for a Heusler alloy-like compound which are known as half-metallic materials with ferromagnetic behaviour. The films have been prepared by means of ultra-high vacuum (UHV) electron beam evaporation with the aim of achieving epitaxial growth on GaAs(100) substrates. The main focus of this work is the structural characterization of the Fe(3)Si films grown on GaAs by means of high resolution transmission electron microscopy (TEM) to confirm the epitaxial growth. For Fe(3)Si with a composition in the vicinity of stoichiometry an almost lattice-matched growth on GaAs(001) has been observed characterized by a high crystalline quality and a good interface perfection. Besides the studies on cross-sectional samples by TEM data from reflection high energy electron diffraction (RHEED) and x-ray diffraction (XRD) were also included into the discussion. The electrical and magnetic parameters of the films studied are found to be in good agreement with data reported for the best Fe(3)Si molecular beam epitaxy (MBE) layers. As evidenced by x-ray diffraction, transmission electron microscopy, resistivity and magnetic measurements, we find an optimum growth temperature of 280-350 degrees C to obtain ferromagnetic layers with high crystal and interface perfection as well as a high degree of atomic ordering.

Structural and magnetic properties of an InGaAs/Fe3Si superlattice in cylindrical geometry.

The structure and magnetic properties of an InGaAs/Fe(3)Si superlattice in a cylindrical geometry are investigated by electron microscopy techniques, x-ray diffraction and magnetometry. To form a radial superlattice, a pseudomorphic InGaAs/Fe(3)Si bilayer has been released from its substrate self-forming into rolled-up microtubes. Oxide-free interfaces as well as areas of crystalline bonding are observed and an overall lattice mismatch between succeeding layers is determined. The cylindrical symmetry of the final radial superlattice shows a significant effect on the magnetization behavior of the rolled-up layers.

[Enkephalin-like immunoreactivity in Leydig cell tumor]. / Immunoréactivité de type enképhaline au sein d'une tumeur à cellules de Leydig.

So far, the presence of an enkephalin-like immunoreactivity has never been reported in Leydig cell tumors at our knowledge. A 39 years old man having a painful gynecomastia and an impotency changing in time has been studied. At clinical examination, he was normal, without palpable testis tumor. The sperm count analysis showed an oligoastheno-spermia. Plasma testosterone (T) was low and plasma estradiol (E2) was high, varying from day to day. T/E2 ratio was always low (20 to 72 - N:220-240) and fell after HCG administration. Plasma LH was normal and plasma FSH was low. 17 hydroxyprogesterone (17 OH-P)/T ratio was increased (0.7 - N:0.23). A small tumor was localized in the left testis by ultrasonography. The spermatic vein catheterization, which was only possible on the left side, showed a decreased T, a high E2 and a low T/E2 ratio (19 - N:304). After unilateral orchidectomy, the histological study confirmed the diagnosis of Leydig cell tumor. With antibodies raised against synthetic Met-en-kephalin, it has been possible to detect an enkephalin-like immunoreactivity in the tumoral cells as well as in the surrounding normal cells.