180 research outputs found
Martensite-like transition and spin-glass behavior in nanocrystalline Pr0.5Ca0.5MnO3
We report on isothermal pulsed (20 ms) field magnetization, temperature
dependent AC - susceptibility, and the static low magnetic field measurements
carried out on 10 nm sized Pr0.5Ca0.5MnO3 nanoparticles (PCMO10). The
saturation field for the magnetization of PCMO10 (~ 250 kOe) is found to be
reduced in comparison with that of bulk PCMO (~300 kOe). With increasing
temperature, the critical magnetic field required to 'melt' the residual
charge-ordered phase decays exponentially while the field transition range
broadens, which is indicative of a Martensite-like transition. The AC -
susceptibility data indicate the presence of a frequency-dependent freezing
temperature, satisfying the conventional Vogel-Fulcher and power laws, pointing
to the existence of a spin-glass-like disordered magnetic phase. The present
results lead to a better understanding of manganite physics and might prove
helpful for practical applications
ESR evidence for disordered magnetic phase from ultra-small carbon nanotubes embedded in zeolite nanochannels
A multi-frequency electron spin resonance (ESR) study provides evidence for
the occurrence of low temperature ferromagnetic/spin-glass behavior in aligned
arrays of sub-nanometer single walled carbon nanotubes confined in zeolite
nano-channels, owing to sp2-type non-bonding carbon associated localized states
with density of ~3 x 1019 /g. Features related to the much anticipated
conduction ESR are not detected. In the paramagnetic phase, the ESR linewidth
is found to be weakly dependent on microwave frequency.Comment: Accepted to be published in EuroPhysics Letter
A deep level transient spectroscopy study of hole traps in GexSe1-x-based layers for ovonic threshold switching selectors
Electron energy band alignment at the (100)Si/MgO interface
The electron energy band diagram at the (100)Si/MgO interface is characterized using internal photoemission of electrons and holes from Si into the oxide. For the as-deposited amorphous MgO the interface barriers correspond to a band gap width of 6.1 eV, i.e., much lower than the conventionally assumed bulk crystal value (7.83 eV). The annealing-induced crystallization of MgO mostly affects the energy of the valence band while the conduction band bottom retains its energy position at 3.37 +/- 0.05 eV above the top of the silicon valence band.(C) 2010 American Institute of Physics. (doi:10.1063/1.3294328
- and -spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects
A study of donor electron spins and spin--dependent electronic transitions
involving phosphorous (P) atoms in proximity of the (111) oriented
crystalline silicon (c-Si) to silicon dioxide (SiO) interface is
presented for [P] = 10 and [P] =
10 at about liquid He temperatures (
). Using pulsed electrically detected magnetic
resonance (pEDMR), spin--dependent transitions between the \Phos donor state
and two distinguishable interface states are observed, namely (i) \Pb centers
which can be identified by their characteristic anisotropy and (ii) a more
isotropic center which is attributed to E defects of the \sio bulk
close to the interface. Correlation measurements of the dynamics of
spin--dependent recombination confirm that previously proposed transitions
between \Phos and the interface defects take place. The influence of these
electronic near--interface transitions on the \Phos donor spin coherence time
as well as the donor spin--lattice relaxation time is then
investigated by comparison of spin Hahn--echo decay measurements obtained from
conventional bulk sensitive pulsed electron paramagnetic resonance and surface
sensitive pEDMR, as well as surface sensitive electrically detected inversion
recovery experiments. The measurements reveal that both and of
\Phos donor electrons spins in proximity of energetically lower interface
states at K are reduced by several orders of magnitude
Analysis of P-b centers at the Si(111)/SiO2 interface following rapid thermal annealing
In this work, an experimental study of defects at the Si(111)/SiO2 interface following rapid thermal annealing (RTA) in a nitrogen ambient at 1040 degreesC is presented. From a combined analysis using electron spin resonance and quasistatic capacitance-voltage characterization, the dominant defects observed at the Si(111)/SiO2 interface following an inert ambient RTA process are identified unequivocally as the P-b signal (interfacial Si-3=Si-.) for the oxidized Si(111) orientation. Furthermore, the P-b density inferred from electron spin resonance (7.8+/-1)x10(12) cm(-2), is in good agreement with the electrically active interface state density (6.7+/-1.7)x10(12) cm(-2) determined from analysis of the quasistatic capacitance-voltage response
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Aryl-viologen pentapeptide self-assembled conductive nanofibers.
A pentapeptide sequence was functionalized with an asymmetric arylated methyl-viologen (AVI3D2) and through controllable β-sheet self-assembly, conductive nanofibers were formed. Using a combination of spectroscopic techniques and conductive atomic force microscopy, we investigated the molecular conformation of the resultant AVI3D2 fibers and how their conductivity is affected by β-sheet self-assembly. These conductive nanofibers have potential for future exploration as molecular wires in optoelectronic applications.ERC (‘ASPiRe’, 240629)
Marie Curie (FP7 ‘SASSYPOL’ ITN, 607602
Electron band alignment between (100)InP and atomic-layer deposited Al2O3
Energy barriers at interfaces of (100)InP with atomic-layer deposited Al2O3 are determined using internal photoemission of electrons. The barrier height between the top of the InP valence band and bottom of the alumina conduction band is found to be 4.05 +/- 0.10 eV corresponding to a conduction band offset of 2.7 eV. An interlayer associated with the oxidation of InP may result in a lower barrier for electron injection potentially leading to charge instability of the insulating stack. A wide-gap P-rich interlayer has a potential to reduce this degrading effect as compared to In-rich oxides. (C) 2010 American Institute of Physics. (doi: 10.1063/1.3496039
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