No abstract

Inelastic slow-neutron scattering experiments are made on polycrystalline samples of intermetallic compounds PrNi, and LaNi, over the temperature range 8 to 295 K. The peaks of the inelastic magnetic-neutron-rare-earth-ion scattering resulting from the splitting of the ion ground state into a number of levels by the crystal electric field (CEF) of hexagonal symmetry are identified by temperature and angular dependence of resonance intensities and by comparing PrNi, spectra with those of LaNi,. On the basis of an effective point charge model for the CEF Hamiltonian with four variable parameters, calculations are made and CEF level scheme is restored. Magnetic contributions to the temperature dependence of heat capacity and magnetic susceptibility of PrKi, are calculated and compared with available experimental data. I m Temperaturbereich von 8 bis 295 I ( werden Untersuchungen der inelastischen Streuung langsamer Neutronen an polykristallinen Proben der intermetallischen Verbindungen PrNi, und LaNi, durchgefiihrt. Die Maxima der inelastischen Streuung magnetischer Neutronen mit lonen Seltener Erden, die aus der Aufspaltung des Grundzustands in eine Zahl von Niveaus des elektrischen Kristallfeldes (CEF) hexagonaler Symmetrie herruhren, werden durch die Temperatur-und Winkelabhangigkeit der Resonanzintensitaten und durch Vergleich der PrNi,-Spektren mit denen von LaNi, identifiziert. Auf der Grundlage eines effektiven Punktladungsmodells fur den CEF-Hamiltonoperator niit vier variablen Parametern werden Rechnungen durchgefuhrt und das CEF-Niveauschema reproduziert. Die magnetischen Beitrage zur Temperaturabhangigkeit der Warmekapazitat und magnetischen Suszeptibilitat von PrNi, werden berechnet nnd mit erhaltlichen experimentellen Werten verglichen.

Tetrahedral amorphous-carbon (ta-C) films were deposited using a filtered cathodic vacuum arc in which nitrogen was incorporated up to an atomic fraction (fN) of 30%. Electrical conductivity and specially thermoelectric power (S) have been performed over a wide range of temperature. The room-temperature conductivity of these samples initially increases with fN up to several orders of magnitude compared to that of ta-C, followed by no dramatic change at higher nitrogen concentration. The sign of the S is negative in the samples with fN below ∼17%, then changes to a positive value with a higher fN. From thermal annealing of the nitrogenated samples a change of the sign of S and its dependence on fN has been analyzed. The small values of both room-temperature S and small variation of conductivity at high fN in all the samples suggest that electrical properties of these films are controlled by compensation of defects.

The electrical transport properties of β-FeSi2 single crystals have been investigated in dependence on the purity of the source material and on doping with 3d transition metals. The transport properties included are electrical conducticvity, Hall conductivity and thermopower mainly in the temperature range from 4K to 300K. The single crystals have been prepared by chemical transport reaction in a closed system with iodine as transport agent. In undoped single crystals prepared with 5N Fe both electrical conductivity and thermopower depend on the composition within the homogeinity range of β-FeSi2 which is explained by different intrinsic defects at the Sirich and Fe-rich phase boundaries. In both undoped and doped single crystals impurity band conduction is observed at low temperatures but above 100K extrinsic behaviour determined by shallow impurity states. The thermopower shows between 100K and 200K a significant phonon drag contribution which depends on intrinsic defects and additional doping. The Hall resistivity is considered mainly with respect to an anomalous contribution found in p-type and n-type single crystals and thin films. In addition doped single crystals show at temperatures below about 130K an hysteresis of the Hall voltage. These results make former mobility data uncertain. Comparison will be made between the transport properties of single crystals and polycrystalline material.

The results are given of crystal field investigations on the cubic intermetallic compound PrMg, by inelastic neutron scattering and specific heat measurement. From the neutron spectra measured a.t T = 8 and 80 K the following crystal field parameters are obtained: B: = -34.7 ; . ' meV and 23: = -89 x meV. The crystal field ground state of Pr3+ is the non-magnetic doublet r3. COO6~aIoTCR pe3yJILTaTbI HCCJIeHOBaHIIR KPHCTaJIJII3l9eCKOI' O nOJIR B ~y6msec~oni IIHTep-MeTaJIJIM' IeCKOM CoeAlTHeHHII PrMg, MeTOAoM HeyllpyrOrO paCCeJ?HHR HefiTpOHOB I3 M3-MepeHHR yAeJIbH0fi TenJIoeMFiOCTII. ~h I J I I I H3MepeHbI CIIeKTphI HeJTIpyrO pacCeHHbIX IIOJIJ? = -34,7 X lllev II @ = -89 :": mCV. OCHOBHOe COCTORHHe Pr3+ He-MarHHTIIbIfi ny6ne~ r3. HeiiTpoHoB npii T = 8 II 80 K. HaiineIrbI cnenymwiie napaMeTpL1 KpmTaxnmecKoro 1) DDR-8051 Dresden, DDR. 2 ) DDR-7010 Leipzig, DDR.