The chemical bond in CdSb

The MO LCAO method is used to show that in CdSb there probably exist electron-deficient bonds in addition to covalent bonds. The proposed bond scheme is compared with the results, obtained up to now with CdSb.The authors thank Dr. A. Línek and Dr. K. Toman for valuable discussions and K. Trnková for performing the numerical calculations.     

Absorption edge of CdSb

Measurements of the absorption of CdSb near the absorption edge at temperatures of 300°, 200°, 80° and 15°K were carried out. The structure of the absorption edge was interpreted by means of indirect allowed transitions.     

Magnetic susceptibility of CdSb doped with Mn,Fe, Ni and La

This paper is devoted to the study of the temperature dependence of the magnetic susceptibility of CdSb doped with Mn, Fe, Ni and La. Analyzing the measured curves on the assumption that the impurities are substitutional and using the Hall constant measurements, we were able to determine the magnetic moments of Fe and Ni impurities and to obtain some information concerning the bond of these atoms with their nearest neighbours. The impurities Mn and La are dissolved in CdSb only partly as substitutional impurities, the major part most probably forming with antimony a new phase which is strongly paramagnetic and fully overgrows the diamagnetism of the parent semiconductor compound.     

Refining of CdSb and preparation of CdSb single crystals by zone melting

CdSb single crystals were prepared by zone melting in a boat both with and without a seed crystal in a stream of pure hydrogen or in a sealed and evacuated tube. The zone moved with a velocity of 1–20 cm/hour. Zone melting in an evacuated tube was used to prepare CdSb single crystals of high purity containing 10¹⁵ acceptors/cm³ at room temperature. During zone refining the stoichiometry is damaged; the front part of the ingot is enriched by cadmium and the end of the ingot by antimony; the enrichment is of an order of several percent after 10 passages of the zone. In the middle part of the ingot the stoichiometric compound remains unchanged. CdSb single crystals grow even by directional cooling of the melt of the stoichiometric compound without a seed crystal.

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CdSb CdSb

CdSb 1–20 cm/, . CdSb CdSb , 10¹⁵ cm³ . ; , . . . CdSb .

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The author died 28. 5. 1961.     

The magnetic susceptibility of TMTSF-DMTCNQ under pressure

The susceptibility of TMTSF-DMTCNQ was measured in the newly discovered highly-conducting state under pressure. At a pressure of 12 kbar, the susceptibility χ_m (with the core diamagnetism subtracted) changes sign from the room-temperature paramagnetic value and becomes diamagnetic at a temperature of approximately 30 K. At a temperature of 5–10 K χ_m reaches a value of approximately ?7 × 10^?4 emu mole^?1. This value is about 3 times larger than the previously reported diamagnetism of HMTSF-TCNQ.     

Infrared spectra of CdSb

We present new measurements of infrared reflectivity of CdSb crystals. Phonons were detected for the three crystallographic axes and fitted with the factorized oscillator model. Fourteen out of the fifteen predicted phonons were detected.     

The maximal magnetic susceptibility of polycrystalline nickel

The two maxima in the susceptibility are shown to arise from irreversible displacement of the 182 ° and 90 ° boundaries; the activation energy arising from the internal stresses is found to be proportional to these.     

Optical properties and band structure of CdSb

The optical constants of CdSb were determined for photon energies up to 2 eV from reflectivity measurements and by using the Kramers-Kronig dispersion relation. The experimental set-up for the reflectivity measurements is described. Possible locations of the observed direct transitions are found by the application of the selection rules. It is shown how these results, together with some results regarding the transport properties of CdSb, can be used to obtain information about the structure of the valence and conduction bands.     

The effective mass of holes in CdSb from reflectivity measurements

From the measured reflectivity near the plasma edge the effective mass of free holes in Ag-doped CdSb was determined. In the studied concentration rangem _b ^* >m _a ^* >m _c ^* is valid. The dependence of the effective mass on the concentration of free holes indicates a strong non-parabolicity of the bands.The authors wish to thank Dr. B. Rheinländer for discussions and information about his results before publication. Mrs. D. Vaková carried out the measurements on UR-10 Zeiss, Mrs. V. Míková prepared the single crystals, Mr. J. Kapar oriented them by X-ray diffraction and Dr. L. Satoura determinedN and. The authors thank them for their help.     

On the band structure of CdSb

The paper consists of two parts. Throughout the first part only the symmetry properties and the existence of the gap are employed for a study of electron bands in CdSb by means of group theory. A general structure of valence bands is obtained, the possible locations of extrema limiting the gap are discussed, and a criterion for the conservation of the gap after switching off the spin-orbit interaction is deduced.In the second part a simple version of thel-dependent pseudopotential suitable for crystals with many atoms in the elementary cell is proposed and the corresponding structure of energy levels in the point is calculated. The results indicate the starting approximation of free electrons to be reasonable and support the hypothesis that the gap arises even before the spin-orbit effects are accounted for.     

Anisotropy of chemical bond in CdSb compound

Mooser's and Pearson's assumption as to the type of bonds in CdSb is confirmed by determining the cleavage, the anisotropy of the linear expansion and to a certain extent also the anisotropy of the amplitude of the thermal vibrations.     

The magnetic susceptibility of single crystals of Zn:Cr

The magnetic susceptibility of single crystals of zinc containing from 46 ppm to 1000 ppm Cr has been measured over the temperature range 4.2–500 K. The susceptibility of the chromium is anisotropic, in the perpendicular direction it is a good fit to a Curie-Weiss type of behaviour with a θ of −0.5 K. At 4.2 K the susceptibility in the parallel direction is 0.90 ± 0.05 of that in the perpendicular direction but a temperatures greater than ≈ 100 K it is larger than the perpendicular susceptibility, the ratio being 1.4 ± 0.1 at 300 K. A model with anisotropic exchange gives good agreement with the anisotropy and its temperature dependence at low temperatures.