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Dive into the research topics where A. Lenard is active.

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Featured researches published by A. Lenard.


Journal of Low Temperature Physics | 1990

Millikelvin studies of mixed-valence HgSe : Fe

A. Lenard; T. Dietl; M. Sawicki; W. Dobrowolski; K. Dybko; T. Skośkiewicz; W. Plesiewicz; S. Miotkowska; A. Witek; A. Mycielski

Resistivity and magnetic susceptibility measurements of HgSe:Fe have been performed down to 30 mK and in the magnetic field range 50 mOe-3 kOe. Previously observed high conductivities of HgSe:Fe in the mixed valence region of Fe donors have been found to remain unchanged down to the lowest measured temperatures, indicating a minor influence of the resonant scattering and Kondo effect. This points to a weak k-d hybridization and substantiates classification of HgSe:Fe as an inhomogeneous mixed-valence system in which intersite Coulomb interactions impose spatial correlations in positions of charged centers. A resistive and inductive indication of superconductivity has been detected in some samples. The phenomenon is assigned to the presence of Hg-related superconducting inclusions and the associated proximity effect. This interpretation explains the field and temperature dependence of the resistivity and magnetic susceptibility, as well as being consistent with a sensitivity of the effect on deviations from stoichiometry and on annealing in Se vapor.


Physica B-condensed Matter | 1994

Second-harmonic generation in a spin-glass microstructure

G. Grabecki; T. Dietl; W. Plesiewicz; A. Lenard; T. Skos´kiewicz; E. Kamin´ska; A. Piotrowska

Abstract We studied magnetoconductance of microregions containing 2d electron-gas adjacent to a grain-boundary plane in bicrystals of Hg0.79Cd0.19Mn0.02Te. In addition to weak localization magnetoresistance and universal conductance fluctuations persisting up to ∼ 1 K, strongly nonlinear-current voltage characteristics were detected in the vicinity of spin-glass freezing occurring at 100 mK.


Journal of Crystal Growth | 1994

Mesoscopic phenomena in a dilute magnetic semiconductor Hg1−x−yCdyMnxTe

G. Grabecki; T. Dietl; W. Plesiewicz; A. Lenard; T. Skośkiewicz; E. Kamińska; A. Piotrowska

Abstract Microscopic four-contact probes to inversion layers adjacent to grain-boundaries of semimagnetic HgCdMnTe have been photolithographically patterned. Magnetoresistance measurements performed on these structures revealed aperiodic conductance fluctuations of the magnitude of the order of e 2 h . Analysis of both fluctuation amplitude and their mean period indicated that the studied system was in mesoscopic regime. Additionally, strongly nonlinear current-voltage characteristics were detected in the vicinity of the spin-glass freezing occurring at T = 100 mK.


Physica B-condensed Matter | 1990

Absence of resonant scattering in mixed valent Hg1χ-FeχSe

A. Lenard; M. Arciszewska; T. Dietl; M. Sawicki; W. Plesiewicz; T. Skoskiewicz; W. Dobrowolaki; K. Dybko

Abstract Resistivity and magnetic susceptibility of Hg 1-χ Fe χ Se have been measured down to 30 mK, in the magnetic field range of 50 mOe - 3 kOe. The data substantiate the classification of Hg l-χ Fe χ Se as an inhomogeneous mixed valence system in which inter-site Coulomb interactions among Fe resonant donors charges impose their spatial correlations, thereby reducing the efficiency of electron scattering. Resistive of superconductivity have been observed in some samples. The phenomenon is assigned to the presence of Hg-related inclusions and the associated proximity effect.


Acta Physica Polonica A | 1991

Conductance Fluctuations in Microstructures of HgCdMnTe Bicrystals

G. Grabecki; A. Lenard; W. Plesiewicz; J. Jaroszyński; Marek Cieplak; T. Skośkiewicz; T. Dietl; E. Kamińska; A. Piotrowska; B. Bulka


Acta Physica Polonica A | 1995

Influence of Bound Magnetic Polarons on Magnetic and Electrical Properties in Metallic n-Cd_{0.95}Mn_{0.05}Se

P. Głód; M. Sawicki; T. Dietl; T. Skośkiewicz; A. Lenard; W. Plesiewicz


Acta Physica Polonica A | 1995

Mesoscopic Phenomena in Microstructures of IV-VI Epilayers

G. Grabecki; T. Dietl; W. Plesiewicz; A. Lenard; T. Skośkiewicz; E. Kamińska; A. Piotrowska; E. Papis; Norbert Frank; G. Bauer


Acta Physica Polonica A | 1993

Second Harmonic Generation in Spin-Glass Microstructures and Fabrication of Microstructures in IV-VI Epilayers

G. Grabecki; T. Dietl; Marek Cieplak; W. Plesiewicz; A. Lenard; T. Skośkiewicz; E. Kamińska; A. Piotrowska; R. Żarecka; G. Springholz; G. Bauer


Acta Physica Polonica A | 1991

Magnetic Susceptibility of Cd_{1-x}Fe_{x}Te_{1-y}Se_{y}

M. Arciszewska; A. Mycielski; W. Dobrowolski; A. Lenard; A. Mauger; B. Witkowska


Acta Physica Polonica A | 1991

Conductivity Near the Metal-to-Insulator Transition in Cd_{1-x}Mn_{x}Se:Sc

P. Głód; M. Sawicki; A. Lenard; T. Dietl; W. Plesiewicz

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T. Dietl

Polish Academy of Sciences

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W. Plesiewicz

Polish Academy of Sciences

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T. Skośkiewicz

Polish Academy of Sciences

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A. Piotrowska

Polish Academy of Sciences

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G. Grabecki

Polish Academy of Sciences

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E. Kamińska

Polish Academy of Sciences

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W. Dobrowolski

Polish Academy of Sciences

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K. Dybko

Polish Academy of Sciences

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