National Institute Of Materials Physics - Romania

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858 articles found

841. MEYER-NELDEL CORRELATION IN SEMICONDUCTORS AND MOTT MINIMUM METALLIC CONDUCTIVITY

Authors: POPESCU, C; STOICA, T

Published: DEC 15 1992, PHYSICAL REVIEW B, 46, 15071, DOI: 10.1103/PhysRevB.46.15063

The paper outlines conditions under which the statistical shift of the Fermi level within the density-of-states (DOS) distribution may result in the Meyer-Neldel correlation. Sufficient conditions have been found: (i) The DOS should have, around the Fermi level, two competing exponential slopes; (ii) The temperature range for the statistical shift should correspond to kT values higher than at least one of these two characteristic energies associated with the slopes. Under such conditions, the Fermi level is no longer the dominant energy for carrier-concentration changes. Relating the Mayer-Neldel correlation to DOS parameters is an essential step in a correct deduction of Mott's minimum-metallic-conductivity value from experiment.

842. GD AMORPHOUS-SILICON OBTAINED FROM TRICHLORSILANE

Authors: POPESCU, C; STOICA, T; DRAGOMIR, A; NENCIU, A; NICOLAE, M; IVAN, P; IONESCU, S

Published: DEC 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 97-8, 1434, DOI: 10.1016/0022-3093(87)90343-7

843. AN EQUATION FOR THE CURRENT VOLTAGE CURVE OF THE A-SI-H SOLAR-CELLS

Authors: POPESCU, C; STOICA, T; SAVANE, AG

Published: JUN 16 1987, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 101, 477, DOI: 10.1002/pssa.2211010219

844. EVALUATION OF THE OPTICAL-CONSTANTS AND THICKNESSES OF WEAKLY ABSORBING NONUNIFORM THIN-FILMS

Authors: GRIGOROVICI, R; STOICA, T; VANCU, A

Published: 1982, THIN SOLID FILMS, 97, 185, DOI: 10.1016/0040-6090(82)90226-7

845. PHOTOCONDUCTIVITY AND PHOTO-VOLTAIC EFFECTS IN SPUTTERED CDTE THIN-FILMS

Authors: CIUREA, ML; BOTILA, T

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 973, DOI:

846. LIGHT-INDUCED-CHANGES IN A-SI-H ANALYZED BY FIELD-EFFECT MEASUREMENTS

Authors: STOICA, T

Published: 1981, JOURNAL DE PHYSIQUE, 42, 410, DOI: 10.1051/jphyscol:1981488

847. TRAPS IN POLYCRYSTALLINE CDTE THIN-FILMS

Authors: CIUREA, ML; BOTILA, T

Published: 1980, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 61, 491, DOI: 10.1002/pssa.2210610220

848. BULK BOUNDARY-CONDITIONS FOR INJECTION AND EXTRACTION IN TRAP-FREE LIFETIME AND RELAXATION SEMICONDUCTORS

Authors: STOICA, T; POPESCU, C

Published: 1978, PHYSICAL REVIEW B, 17, 3983, DOI: 10.1103/PhysRevB.17.3972

849. PHOTOCONDUCTIVITY IN A-GESE

Authors: VESCAN, L; STOTZEL, H; STOICA, T; KOTTWITZ, A

Published: 1978, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 87, 246, DOI: 10.1002/pssb.2220870128

850. EXCHANGE COUPLED NANOCOMPOSITES: MAGNETOPLUMBITE Sr FERRITE AND MAGNETITE

Authors: Greculeasa, SG; Comanescu, C; Iacob, N; Kuncser, A

Published: , ROMANIAN JOURNAL OF PHYSICS, 2022, DOI: 606

Exchange coupling in a SrFe12O19 - Fe3O4 nanocomposite magnet was explored in this study. The composition, microstructure, local structure and magnetic properties were investigated by XRD, SEM, Mossbauer spectroscopy, and SQUID magnetometry. The magnetoplumbite SrFe12O19 and spinel Fe3O4 structures were verified by X-ray diffraction. The morphology of the composite reveals the characteristics of the two components. The hyperfine parameters allowed the identification of the Wyckoff positions of the iron ions corresponding to the involved phases. The magnetic measurements of the composite, showing a single-phase-like magnetic hysteresis loop, confirmed the exchange coupling between the hard and soft magnetic phases.