National Institute Of Materials Physics - Romania

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5840 articles found

5281. EVIDENCE FOR SPIN FREEZING AND FERROMAGNETIC SHORT-RANGE CORRELATIONS IN FE-57-DOPED LINIO2

Authors: FILOTI, G; ROSENBERG, M; STELMASZYK, P; ZHOU, R; KEMMLERSACK, S; KLEIN, V

Published: 1994, HYPERFINE INTERACTIONS, 88, 95, DOI: 10.1007/BF02068706

Evidence for a frozen spin ground state and a mixed magnetic ordered and paramagnetic state at intermediate temperatures was found in Fe-57-doped LiNiO2, using Mossbauer spectroscopy. The magnetic measurements, in agreement with Mossbauer data, suggest short-range ferromagnetic correlations at low temperatures and the occurrence of a paramagnetic phase below the spin freezing temperature.

5282. HIGH-FIELD MOSSBAUER STUDY OF THE RANDOMLY CANTED LI-FE-TI SYSTEM

Authors: SEQQAT, M; DORMANN, JL; NOGUES, M; JOVE, J; NICOARA, G

Published: 1994, HYPERFINE INTERACTIONS, 94, 2021, DOI: 10.1007/BF02063733

In-field Mossbauer studies have been performed on the Li-0.5(1+t)(l+r)Fe2.5-1.5tTitO4 system with 1.10 less than or equal to t less than or equal to 1.40. The disordered magnetic properties depend strongly on the chemical disorder and local order induced by thermal treatments. The results are in agreement with low- and high-field magnetization measurements. Locally canted states are observed, with the degree of magnetic disorder depending on the composition and (or) the local chemical disorder.

5283. LINE-SHAPE MODEL FOR THE BROAD PHOTOLUMINESCENCE BAND FROM SI1-XGEX/SI HETEROSTRUCTURES

Authors: HARTMANN, A; VESCAN, L; DIEKER, C; STOICA, T; LUTH, H

Published: DEC 15 1993, PHYSICAL REVIEW B, 48, 18279, DOI: 10.1103/PhysRevB.48.18276

Photoluminescence studies on Si1-xGex layers exceeding the critical thickness show not only dislocation-related peaks D1,...,D4, but also in addition a broad band (T band), centered at similar to 110 meV below the strained alloy band gap. Depth profiling studies show that the T band is due to centers in the Si1-xGex. The excitation power dependence and high quantum efficiency of the T band can be explained by assuming that it is due to an isoelectronically trapped exciton. T-band line shapes were fitted by a model based on statistical fluctuations of the Ge content and their effect on the local gap energy.

5284. TIN TETRACHLORIDE INTERACTION WITH HUMAN HEMOGLOBIN

Authors: FRUNZA, L; SERBANESCU, RM

Published: DEC 1993, GENERAL PHYSIOLOGY AND BIOPHYSICS, 12, 516, DOI:

In the presence of tin tetrachloride, the rate constant for the rebinding of CO to the triliganded hemoglobin, l'(4), is much increased and the number of molecules participating in the CO ligation is decreasing. The pH drops, but a proton consumption process also takes place at the same time. The heme and its environment do not seem to change much, but the tin complexing to protein is very probable. The oxidation of hemoglobin in the form of either oxy or carbonmonoxy occurs with rather high rate.

5285. CONDUCTIVITY OF 2-STATE TRAPPING MODELS BEYOND MEAN-FIELD

Authors: PITIS, R

Published: NOV 29 1993, PHYSICS LETTERS A, 183, 84, DOI: 10.1016/0375-9601(93)90893-5

The uniform one-dimensional and square lattice hopping models are considered, where particles can be in one of two states at each site. Transport takes place by nearest neighborjumps between upper energy states. Trapping in lower energy states introduces correlations, the effect of which on the dc conductivity is estimated in the first step beyond the mean-field approximation.

5286. MAGNETIC-PROPERTIES OF FE100-XGDX THIN-FILMS AND FE80-XGDXB20 THIN-FILMS AND RIBBONS (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-20)

Authors: FILOTI, G; KUNCSER, V; SERBANESCU, MD; JIANU, A; CRISTEA, L; NOGUES, M; DORMANN, JL; MAKNANI, J

Published: NOV 1993, IEEE TRANSACTIONS ON MAGNETICS, 29, 3125, DOI: 10.1109/20.280879

Magnetic and Mossbauer experiments were performed on Fe100-xGdx thin films and on Fe80-xGdxB20 both in thin films and ribbons for x less-than-or-equal-to 20. The ferrimagnetic order is perturbed by the presence of B and Fe-interactions are.different. For small Gd content, the low anisotropy is in the film plane, while for greater Gd the anisotropy goes out of the plane giving typical features of hysteresis loops and strong decrease of Mossbauer hyperfine fields.

5287. ND3+ MULTISITES IN THE DISORDERED CA3GA2GE3O12 LASER CRYSTAL

Authors: CALDINO, U; VODA, M; JAQUE, F; SOLE, JG; KAMINSKII, AA

Published: OCT 1 1993, CHEMICAL PHYSICS LETTERS, 213, 88, DOI: 10.1016/0009-2614(93)85422-K

Laser excited site-selective spectroscopy of Nd3+ ions in Ca3Ga2Ge3O12 garnet crystals has been investigated in the F-4(3/2)-->I-4(11/2) and F-4(3/2)-->I-4(9/2) regions. Six non-equivalent sites were observed for the Nd3+ in this material. The energy levels of some relevant multiplets were obtained for each Nd3+ site. The evolution of the non-equivalent Nd3+ CryStal field sites in Ca3Ga2Ge3O12 as a function of dopant concentration has been investigated in the range up to 8 at%. The nature of the Nd3+ sites in terms of the possible charge compensating defects is discussed. The formation of Nd3+-Nd3+ pairs is suggested.

5288. ELECTRON-IRRADIATION EFFECT ON VACUUM-EVAPORATED CDS THIN-LAYERS

Authors: CRISTEA, P; SPANULESCU, I; SECAREANU, I; RUXANDRA, V; SPANULESCU, S; BALTATEANU, N

Published: SEP 15 1993, JOURNAL OF MATERIALS SCIENCE LETTERS, 12, 1469, DOI: 10.1007/BF00591610

5289. HISTORY DEPENDENT STRUCTURAL-PROPERTIES OF ALUMINA-SUPPORTED NICKEL-OXIDE

Authors: CRAIU, M; MARCHIDAN, R; IVANA, E; BUTUCELEA, A; NISTOR, L

Published: SEP 1993, REACTION KINETICS AND CATALYSIS LETTERS, 50, 32, DOI: 10.1007/BF02062185

The formation of nickel oxide from Ni-Al takovite-like compounds has been investigated. Information about the stoichiometry of the NiO phase obtained by Diffuse Reflectance (DR) spectroscopy is discussed in connection with TPR and solubility data.

5290. SIO2-SM2O3 VITREOUS FILMS VIA THE SOL-GEL METHOD

Authors: ZAHARESCU, M; PIRLOG, C; GARTNER, M; MOISE, F; TEODORESCU, V

Published: AUG 15 1993, JOURNAL OF MATERIALS SCIENCE, 28, 4441, DOI: 10.1007/BF01154953

SiO2-Sm2O3 vitreous films 120 nm thick were obtained via the sol-gel method. Infrared, energy-dispersive analysis of X-rays, spectroscopic ellipsometry and absorption spectroscopy showed a total inclusion of samarium in the silica matrix, which remains amorphous up to 1000-degrees-C. The inclusion of the samarium ion increases the porosity. The optical properties of films were investigated by spectro-ellipsometry, and the parameters obtained were compared with those obtained by other techniques.