Magnon instability in the free-carrier absorption in magnetic semiconductors under a strong d.c. magnetic field

The magnon damping in an electron-magnon system in the presence of a laser beam and a d.c. magnetic field is discussed. It is shown that near the laser-cyclotron resonance, and for the laser beam propagating perpendicularly to the magnetic field the magnon population in a relatively narrow range of k may grow with time.     

Spin wave amplification by a radiation field in free-carrier magnetic semiconductors

The rate of change in the magnon population due to scattering by free carriers in the presence of a laser field is calculated. It is found that spin waves propagating parallel to the direction of propagation of the radiation field may be amplified over a relatively narrow band of q values.     

L 0 - phonon instability in the free-carrier absorption in semiconductors under strong magnetic fields

The LO- phonon damping in an electron-phonon system in the presence of a laser beam and a d. c. magnetic field is discussed. It is shown that near the laser-cyclotron resonance, and for the laser beam propagating perpendicularly to the magnetic field the LO-phonon population in a relatively narrow range of $\text{K}$ may grow with time.     

Synthesis and spectroscopic characterization of copper(II) tetraazaiminooxime macrocyclic complexes--a tetragonal distortion analysis

Herein we describe the synthesis and spectroscopic (infrared and UV-vis) analysis of [Cu(II)(dohpn)(L)](n+) (dohpn=imineoximic tetraazamacrocyclic ligand 2,3,9,10-tetramethyl-1,4,8,11-tetraazaundecane-1,3,8,10-tetraen-11-ol-1-olate) and L=SCN(-), I(-), Cl(-) (n=0) and 4-aminopyridine (ampy), 4,4'-bipyridine (bipy), imidazole (im), 2-aminopyrazine (ampz) and water (n=1+). The following order of the Jahn-Teller stabilization energy (cm(-1)) was observed: I(-)(6452)相似文献   

Synthesis, characterization and semi-empirical calculations for the thiocyanate linkage isomers of an (alpha-iminooxime)cobalt(III) macrocyclic complex

Herein we report the synthetic route and detailed characterization of the macrocyclic complex [Co(dohpn)(SCN)2] and its linkage isomer (dohpn=2,3,9,10-tetramethyl-1,4,8,11-tetraazaundecane-1,3,8,10-tetraen-11-ol-1-olate and py=pyridine) based on analytical, spectroscopic and electrochemical methods. Structural, vibrational and electronic features are discussed and a coherent assignment is proposed on the basis of semi-empirical theoretical calculations.     

Energy decay and control for a system of strings elastically connected in parallel

In the present paper, we study energy decay and exact boundary controllability for a system of n one-dimensional linear wave equations coupled in parallel. The control obtained is a square integrable of the Neuman type for initial data with finite energy. The controllability time is near optimal value. We treat the case of control in the whole boundary and also in part of it.     

Antidiarrhoeic effect and dereplication of the aqueous extract of Annona crassiflora (Annonaceae)

We investigated the antidiarrhoeic effect of the aqueous extract of Annona crassiflora leaves (AEAC). The AEAC decreased the diarrhoeic stools and enteropooling induced by castor oil, without altering total faecal output; moreover, the distance travelled by charcoal meal in the intestine was increased. Twenty-eight compounds were identified by LC-DAD-MS in the AEAC, including flavonoids, alkaloids and proanthocyanidins. In addition, two oligomeric series of condensed tannins of up to nine flavan-3-ol units were characterised by MALDI-MS. These data suggest that the antidiarrhoeic effect of the AEAC is related to its ability to inhibit intestinal secretion and/or to increase intestinal absorption. Moreover, the prokinetic effect of AEAC, together with its inhibitory effect on enteropooling induced by castor oil, explains why this extract decreased diarrhoeic faeces without altering the total faecal output. All these effects are in agreement with the pharmacological activity reported in the literature for many of the secondary metabolites identified.     

Kohn-Sham theory of an atomic Fermi gas

We point out that, when repulsive interactions between two fermions are not integrable, as the case may be for atomic fermions, the original Kohn-Sham density functional must be revised.     

Structural and magnetic properties of nanocrystalline particles in an amorphous Fe73.5Nb3CuSi13.5B9 matrix

We report structural and magnetic properties of fine particles embedded in an amorphous magnetic matrix. As-quenched amorphous Fe_73.5Nb₃CuSi_13.5B₉ ribbons (FINEMET) were submitted to the thermal treatments of several times (1 ? t ? 240 min) at 570 °C using a conventional furnace. The analyses of the X-ray diffraction patterns at room temperature reveal that our samples consist of single phase Fe₃Si nanocrystals embedded in a residual amorphous phase. Magnetic measurements show that the saturation moment at T = 450 °C increases as a function of annealing time. This behavior is attributed to an increase of the fraction of nanocrystallites in the residual amorphous phase.