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Tytuł:
Critical Exponents for Metal-Insulator Transition in Two-Dimensional Systems
Autorzy:
Wojtkiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1808033.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.10.Fd
02.40.Xx
Opis:
Three years ago, a new universality class, associated with the metal-insulator transition in quasi-two-dimensional compounds, was discovered. Imada has given explanation of the observed critical behaviour. Considerations in this work are based on the assumption that the one-particle dispersion is quartic one instead of the standard quadratic behaviour. In this paper, it is shown that other possible natural non-standard dispersions lead to other possible critical behaviour and critical exponents.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 931-934
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me=Cr, Fe) cobaltites
Autorzy:
Troyanchuk, I.
Bushinsky, M.
Tereshko, N.
Fedotova, V.
Powiązania:
https://bibliotekanauki.pl/articles/118524.pdf
Data publikacji:
2015
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
magnetic interactions
magnetization
magnetoresistance
metal-insulator transition
oddziaływania magnetyczne
namagnesowanie
magnetorezystancja
przejście metal-izolator
Opis:
Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me = Cr, Fe) stoichiometric cobaltites has been investigated in magnetic fields up to 14 T. It is shown that doping with Fe ions changes spontaneous magnetization only slightly herewith the Curie point significantly decreases. The chromium doping leads to dramatic decrease of magnetization and the Curie point and a strong increase in magnetoresistance at low temperature. The obtained results indicate that the magnetic interactions between Co and Fe are positive whereas those between Co and Cr ions are negative. Enhancement of magnetoresistance is attributed to the magnetic field induced transition from antiferromagnetic order to ferromagnetic one.
Właściwości magnetyczne i magnetotransportowe stoichiometrycznych kobaltytów zbadano w polach magnetycznych do 14T. Ustalono, że domieszkowanie przez jony Fe zmienia namagnesowanie spontaniczne bardzo słabo w tym czasie jak punkt Curie obniża się znacząco. Domieszkowanie przez atomy chromu powoduje dramatyczne zmniejszenie namagnesowania i obniżenie punktu Curie i mocny wzrost magneto rezystancji w niskich temperaturach. Otrzymane rezultaty wskazują oddziaływanie magnetyczne pomiędzy Co i Fe jest pozytywne w tym czasie jak pomiędzy Co a Cr jest negatywne. Wzmocnienie magnetorezystancji przypisano do pola magnetycznego indukowanego przejściem z antyferromagnetycznego układu do ferromagnetycznego.
Źródło:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej; 2015, 8; 69-76
1897-7421
Pojawia się w:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Diagram of Metal-Insulator Transition in System with Anderson-Hubbard Centers
Autorzy:
Skorenkyy, Yu.
Didukh, L.
Kramar, O.
Dovhopyaty, Yu.
Powiązania:
https://bibliotekanauki.pl/articles/1418528.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.30.+h
Opis:
The model of a strongly correlated system in which periodically spaced Anderson-Hubbard centers are introduced into narrow-band metal is considered. Besides the interactions between localized magnetic moments and strong on-site Coulomb interaction, the model takes into account the hybridization of localized and band states. To study the effect of the lattice deformation on the electrical properties of the system, the phonon term and elastic energy have been taken into account. Green functions for band and localized electrons have been found. On this base, the energy spectrum has been investigated as a function of model parameters, temperature and external pressure. The criterion of the metal-insulator transition for an integer value of electron concentration has been derived and the phase diagram of the metal-insulator transition has been built.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 532-534
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin and lattice dynamics of La2/3Ca1/3MnO3 doped with 1% 119Sn
Autorzy:
Przewoźnik, J.
Żukrowski, J.
Chmist, J.
Japa, E.
Kołodziejczyk, A.
Krop, K.
Kellner, K.
Gritzner, G.
Powiązania:
https://bibliotekanauki.pl/articles/147199.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
119Sn Mössbauer
LCMO manganites
f-factor
metal-insulator
Opis:
1 at.% 119Sn doped La0.67Ca0.33MnO3 compound was studied by Mössbauer spectroscopy, magnetization, AC susceptibility and resistivity measurements. Huge separation (66 K) of the transition temperatures from the ferromagnetic (FM) to paramagnetic (PM) state (TC) and from metallic to insulating state (TM-I) clearly shows that transition from FM metallic to PM insulator phase goes via FM insulator phase. The Mn lattice dynamics was studied by the relative changes of Lamb-Mössbauer factor f as a function of temperature. In the Debye approximation from the calculated ln(f/f0) values of the characteristic Debye temperatures (čD) were estimated for the FM (368(10) K) and PM (391(6) K) phases. No anomaly of -ln(f/f0) at TM-I and its rather spurious increase around TC was found. The 119Sn isotope as a local diamagnetic probe samples the transferred hyperfine field (Bhf) from its neighbour Mn magnetic moments and witnesses the dynamics of the Mn moments. Theoretical curve based on the molecular field theory was fitted to the experimental values of Bm hf ax and the value of the ordering temperature (TC * H 280 K) of Mn moments inside the large FM domains was estimated. It is much higher than the TC (172 K) obtained from magnetization measurement. The coexistence of FM and PM phases, which is evident from the shape of our 119Sn Mössbauer spectra, was confirmed for temperatures T e 150 K and indicates the inhomogeneous character of the magnetic transition.
Źródło:
Nukleonika; 2004, 49,suppl.3; 37-42
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Model for Metal-Insulator Transition in Amorphous Gd_{x}Si_{1-x}
Autorzy:
Paja, A.
Ornat, M.
Powiązania:
https://bibliotekanauki.pl/articles/1399304.pdf
Data publikacji:
2013-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Cz
72.15.Lh
72.15.Rn
Opis:
The model for experimentally observed metal-insulator transition induced by magnetic field in amorphous $Gd_{x}Si_{1 - x}$ is presented. The method of calculation is based on the previously created model for amorphous alloys now developed to include magnetic field effects. The model is based on the quantum "2 $k_{F}$" scattering model theory where the pseudopotentials are replaced by the scattering matrix operators and the Fermi energy is properly determined by the accurate values of the phase shifts. The results agree very well with experimental data.
Źródło:
Acta Physica Polonica A; 2013, 124, 4; 717-719
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Challenges for 10 nm MOSFET process integration
Autorzy:
Östling, M.
Malm, B. G.
Haartman, M.
Hallstedt, J.
Zhang, Z.
Hellström, P. E.
Zhang, S.
Powiązania:
https://bibliotekanauki.pl/articles/309004.pdf
Data publikacji:
2007
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
sstrained silicon
silicon-germanium
silicon-on-insulator (SOI)
high-k dielectrics
hafnium oxide
nanowire
low frequency noise
mobility
metal gate
Opis:
An overview of critical integration issues for future generation MOSFETs towards 10 nm gate length is presented. Novel materials and innovative structures are discussed. The need for high-k gate dielectrics and a metal gate electrode is discussed. Different techniques for strain-enhanced mobility are discussed. As an example, ultra thin body SOI devices with high mobility SiGe channels are demonstrated.
Źródło:
Journal of Telecommunications and Information Technology; 2007, 2; 25-32
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-dimensional modeling of surface photovoltage in metal/insulator/n-GaN structure with cylindrical symmetry
Autorzy:
Matys, M
Powroznik, P
Kupka, D
Adamowicz, B
Powiązania:
https://bibliotekanauki.pl/articles/174326.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
surface photovoltage
gallium nitride
metal-insulator-semiconductor (MIS) structure
interface states
photodetector
Opis:
The rigorous numerical analysis of the surface photovoltage (SPV) versus excitation UV-light intensity (Φ), from 104 to 1020 photon/(cm2s) in a metal/insulator/n-GaN structure with a negative gate voltage (VG = –2 V) was performed using a finite element method. In the simulations we assumed a continuous U-shape density distribution function Dit(E) of the interface states and n-type doping concentration ND = 1016 cm–3. The SPV signal was calculated and compared in three different characteristic regions at the interface, namely i) under the gate centre, ii) near the gate edge and iii) between the gate and ohmic contact. We attributed the differences in SPV(Φ) dependences to the influence of the interface states in terms of the initial band bending and interface recombination controlled by the gate bias. The obtained results are useful for the design of GaN-based UV-radiation photodetectors.
Źródło:
Optica Applicata; 2013, 43, 1; 47-52
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal-Insulator Transition in Zinc-Doped LaSrCuO
Autorzy:
Malinowski, A.
Cieplak, M. Z.
Berkowski, M.
Plesiewicz, W.
Skośkiewicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/2046782.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
71.30.+h
74.25.Fy
Opis:
The magnetotransport in the vicinity of the metal-insulator transition in La$\text{}_{1.85}$Sr$\text{}_{0.15}$Cu$\text{}_{x}$Zn$\text{}_{1-x}$O$\text{}_{4}$ is studied in the mK temperature range. Both longitudinal and transverse magnetoresistance are negative indicating the importance of spin effects. The magnitude of transverse magnetoresistance is larger than the magnitude of longitudinal magnetoresistance, indicating the absence of positive orbital magnetoresistance, in sharp contrast to strongly underdoped La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$. Both transverse and longitudinal magnetoresistance are proportional to the relative change of zero-field conductivity. This suggests that low-temperature localization of carriers may originate in the spin-disorder scattering on the spin droplets around Zn-impurities.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 617-621
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal-Insulator Transition in Doped Semiconductors
Autorzy:
Jaroszyński, J.
Powiązania:
https://bibliotekanauki.pl/articles/1888088.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
Opis:
A survey is given of different kinds of metal-insulator transitions (MIT) in doped semiconductors. The role of electron-electron Coulomb interactions and of disorder is discussed vis-a-vis millikelvin experimental results for semimagnetic semiconductors (SMSC) in the vicinity of MIT. Critical behavior of conductivity tensor components and dielectric susceptibility at the magnetic field-induced MIT in p-type Hg$\text{}_{1-x}$Mn$\text{}_{x}$Te is compatible with the model in which the MIT is a result of quantum localization driven by disorder-modified electron-electron interactions. At the same time the critical behavior of the Hall coefficient suggests that, in addition to electrons forming the Fermi liquid (FL) and undergoing localization at the MIT, there is certain a concentration of local electron moments, even on the metallic side of the MIT. The formation of these moments can presumably be described in terms of a disordered Hubbard-Mott model.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 255-265
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of gate leakage current components in metal-insulator-semiconductor structures with high-k gate dielectris
Autorzy:
Janik, T.
Jakubowski, A.
Majkusiak, B.
Korwin-Pawłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/308423.pdf
Data publikacji:
2001
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
MIS structures
ultrathin dielectrics
high-k dielectrics
Opis:
Numerical simulations of the gate leakage current in metal-insulator-semiconductor (MIS) structures based on the transfer matrix approach were carried out. They show contribution of different components of this current in MIS structures with best known high-k dielectrics such as Ta2O5 and TiO2. The comparison of the gate leakage current in MIS structures with SiO2 layer as well Ta2O5 and TiO2 layers is presented as well. Additionally, the minimum Si electron affinity to a gate dielectric which allows to preserve given level of the gate leakage current is proposed.
Źródło:
Journal of Telecommunications and Information Technology; 2001, 1; 65-69
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation-Driven Metal-Insulator Transitions
Autorzy:
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2011236.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.45.Gm
Opis:
The effect of correlation-driven electronic transitions are described for the V$\text{}_{2}$O$\text{}_{3}$, NiS$\text{}_{2-x}$Se$\text{}_{x}$, and Fe$\text{}_{3}$O$\text{}_{4}$ systems. The various tranformations can all be rationalized in terms of elementary concepts pertaining to the Mott-Hubbard intraatomic electronic interactions or in terms of an order-disorder formalism involving Coulomb interactions among electrons on adjacent sites. Attention is directed to some outstanding issues that require further resolution.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 141-156
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic Analysis of Metal-Insulator Transitions. Effect of Changes in the Density of States Function
Autorzy:
Hoehn, R.
Honig, J.
Powiązania:
https://bibliotekanauki.pl/articles/1808133.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Hf
71.20.-b
71.10.Ay
71.30.+h
71.45.Gm
Opis:
Prior theories of metal-insulator transitions by Spałek et al. were extended to include quartic terms in the temperature and by introducing two different density of state functions. The effects of these extensions on low-temperature metal-insulator transitions and on reentrant metallic behavior in solids have been investigated.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 745-754
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reentrant Metal-Insulator Transition in $Ca_{1-x}Eu_{x}B_{6}$
Autorzy:
Glushkov, V.
Anisimov, M.
Baybakov, R.
Demishev, S.
Filippov, V.
Flachbart, K.
Kuznetsov, A.
Shitsevalova, N.
Sluchanko, N.
Powiązania:
https://bibliotekanauki.pl/articles/1369362.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.Gd
75.47.Gk
Opis:
Resistivity, Hall and Seebeck effects have been studied on single crystals of $Ca_{1-x}Eu_{x}B_{6}$ (0 ≤ x ≤ 1) at temperatures 2-300 K and in magnetic fields up to 8 T. An insulating ground state is found to be limited by narrow range of Eu doping 0.6 ≤ x ≤ 0.8. This region is characterized by an enhanced colossal magnetoresistance (CMR), which reaches values of ρ(0)/ρ(7T) > $10^{6}$ for x = 0.63 at T < 10 K. Decreasing of Eu content in $Ca_{1-x}Eu_{x}B_{6}$ below x* ≈ 0.6 restores the metallic ground state with moderate resistivity (ρ ~ 1 ÷ 5 mΩ·cm) and CMR amplitude (ρ(0)/ρ(7T) < 7). The second metal-insulator transition (MIT) in $Ca_{1-x}Eu_{x}B_{6}$ is observed beyond the whole conductivity region found earlier in the narrow range of Eu doping (0.7 ≤ x ≤ 0.8). The correlation between the enhanced CMR amplitude, the onset of positive diffusive thermopower and the elevation of anomalous Hall effect, determined for Eu content 0.6 ≤ x ≤ 0.85, favors the idea that a smooth change of band structure is the main factor governing the reentrant MIT in $Ca_{1-x}Eu_{x}B_{6}$.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 294-295
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity Near the Metal-to-Insulator Transition in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Se:Sc
Autorzy:
Głód, P.
Sawicki, M.
Lenard, A.
Dietl, T.
Plesiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1887158.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.55.Jv
Opis:
Earlier studies of transition metal impurities in II-VI compounds suggest that Sc acts as a resonant donor. We performed Hall effect and conductivity measurements of CdSe:Sc and Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se:Sc. The results, particularly the critical concentration of the metal-to-insulator transition, turned out to be similar to those obtained previously for Cd$\text{}_{1-x}$Mn$\text{}_{x}$Se doped with hydrogenic-like impurities, such as In and Ga. Therefore, if the ground state of Sc impurity is indeed located above the bottom of the conduction band, our data demonstrate that the metal-to-insulator transition is primarily driven by the scattering, i.e. it corresponds to the Anderson localization.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 389-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Matrix onto Oxidation of Metallic Nanoparticles in Metal-Insulator Nanocomposite Films
Autorzy:
Fedotova, J.
Powiązania:
https://bibliotekanauki.pl/articles/1381794.pdf
Data publikacji:
2014-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Gk
73.40.Rw
73.63.Bd
62.23.Pq
68.37.Lp
68.37.Og
Opis:
Paper reports the results of X-ray diffraction, X-ray absorption spectroscopy and the Mössbauer spectroscopy of metal-insulator films sintered in Ar+O atmosphere evidencing the difference in oxidation of FeCoZr nanoparticles embedded into $Al_2O_3$ and $Pb(ZrTi)O_3$ matrixes. It is proved that $Al_2O_3$ matrix with high resistance to oxidation favors the formation of nanoparticles with "metal core-oxide shell" structure, while fully oxidized nanoparticles are observed inside $Pb(ZrTi)O_3$ matrix.
Źródło:
Acta Physica Polonica A; 2014, 125, 6; 1418-1420
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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