60 research outputs found
Al-Substitution Effects on Physical Properties of the Colossal Magnetoresistance Compouns La0.67ca0.33mno3
We present a detailed study of the polycrystalline perovskite manganites
La0.67Ca0.33AlxMn1-xO3 (x = 0, 0.1, 0.15, 0.5) at low temperatures and high
magnetic fields, including electrical resistance, magnetization, ac
susceptibility. The static magnetic susceptibility was also measured up to 1000
K. All the samples show colossal magnetoresistance behavior and the Curie
temperatures decrease with Al doping. The data suggest the presence of
correlated magnetic clusters near by the ferromagnetic transition. This appears
to be a consequence of the structural and magnetic disorder created by the
random distribution of Al atoms.Comment: 13 pages including 5 figure
CONSEQUENCES OF META-LINGUISTICS PARTICIPATION ON THE OPERATIONALIZATION OF DYNAMIC MANAGEMENT DOXASTIC LOGIC
The paper starts from the thesis that proves non-invasive behavioral explaining differences, but the existence of operational priorities of the company / entity / enterprise lead to invasiveness. There are no known ways / methods / programming doxastic methods as long as management intervention can be treated as a hub that dominates hypertext / productive economic common rules the world. The phenomenon of identity management is far from meeting the full harmonization attitudinal decision-making process. Doxastic management is a new epistemological covered by copyright scientifically in 2013 (Ioan Gaf-Deac, Fundamentals of Doxastic Management, Ed. FMP, Bucharest, 2013, 508 pp., Sole author, ISBN 978-606-93321-5 -3). The paper described aspects of doxastic procedural behavior, situations tangible managerial decision in doxastic field. They are played and the comparison between deterministic doxastic systems analysis and managerial phenomena is considered to operationalize participation of doxastic meta-linguistic logic of dynamic management. Doxastic management simplicity and demarcation or limitation of positive action by doxastic management round alignments research
MEASUREMENT OF INTANGIBLE ASSETS IN RECOVERY AREAS AND OPERATION OF NATURAL RESOURCES
The paper shows that to date, intangible assets are considered "goods" and as such, the practice of classical accounting consider intellectual capital in the same category of "goods equivalent / similar to those visible / tangible". From research that literature on measuring knowledge assets / intellectual capital, both in Romania and worldwide, is not large enough and does not provide finite significant "strong" on classifications semantic of the content and quality issues in the field. The book titled New Economy between knowledge and risk – Infomin Ed., Deva, 2010 (www.infomindeva.ro) (ISBN 978-973-7646-11-8), (Ioan I. Gâf-Deac)  presents systematization and classification of original models and methodologies for measuring knowledge assets, intellectual capital in socio-economic sciences, and as such, in this present article resorting to the extension applied to formalizing measurement of intangible assets in areas operation and exploitation of natural resources
Experimental determination of superconducting parameters for the intermetallic perovskite superconductor ${\text {MgCNi}}_3
We have measured upper-critical-field , specific heat C, and
tunneling spectra of the intermetallic perovskite superconductor MgCNi
with a superconducting transition temperature K. Based
on these measurements and relevant theoretical relations, we have evaluated
various superconducting parameters for this material, including the
thermodynamic critical field (0), coherence length (0),
penetration depth (0), lower-critical-field (0), and
Ginsberg-Landau parameter (0). From the specific heat, we obtain the
Debye temperature 280 K. We find a jump of
=2.3 at (where is the
normal state electronic specific coefficient), which is much larger than the
weak coupling BCS value of 1.43. Our tunneling measurements revealed a gap
feature in the tunneling spectra at with 4.6, again larger than the weak-coupling value
of 3.53. Both findings indicate that MgCNi is a strong-coupling
superconductor. In addition, we observed a pronounced zero-bias conductance
peak (ZBCP) in the tunneling spectra.
We discuss the possible physical origins of the observed ZBCP, especially in
the context of the pairing symmetry of the material.Comment: 5 pages, 4 figure
Phase Separation and the Low-Field Bulk Magnetic Properties of Pr0.7Ca0.3MnO3
We present a detailed magnetic study of the perovskite manganite
Pr0.7Ca0.3MnO3 at low temperatures including magnetization and a.c.
susceptibility measurements. The data appear to exclude a conventional spin
glass phase at low fields, suggesting instead the presence of correlated
ferromagnetic clusters embedded in a charge-ordered matrix. We examine the
growth of the ferromagnetic clusters with increasing magnetic field as they
expand to occupy almost the entire sample at H ~ 0.5 T. Since this is well
below the field required to induce a metallic state, our results point to the
existence of a field-induced ferromagnetic insulating state in this material.Comment: 15 pages with figures, submitted to Physical Review
Magnetic relaxation in La0.250Pr0.375Ca0.375MnO3 with varying phase separation
We have studied the magnetic relaxation properties of the phase-separated
manganite compound La0.250Pr0.375Ca0.375MnO3 . A series of polycrystalline
samples was prepared with different sintering temperatures, resulting in a
continuous variation of phase fraction between metallic (ferromagnetic) and
charge-ordered phases at low temperatures. Measurements of the magnetic
viscosity show a temperature and field dependence which can be correlated to
the static properties. Common to all the samples, there appears to be two types
of relaxation processes - at low fields associated with the reorientation of
ferromagnetic domains and at higher fields associated with the transformation
between ferromagnetic and non-ferromagnetic phases.Comment: 30 pages with figures, PDF, accepted to be published in Physical
Review
Time-resolved detection of spin-transfer-driven ferromagnetic resonance and spin torque measurement in magnetic tunnel junctions
Several experimental techniques have been introduced in recent years in
attempts to measure spin transfer torque in magnetic tunnel junctions (MTJs).
The dependence of spin torque on bias is important for understanding
fundamental spin physics in magnetic devices and for applications. However,
previous techniques have provided only indirect measures of the torque and
their results to date for the bias dependence are qualitatively and
quantitatively inconsistent. Here we demonstrate that spin torque in MTJs can
be measured directly by using time-domain techniques to detect resonant
magnetic precession in response to an oscillating spin torque. The technique is
accurate in the high-bias regime relevant for applications, and because it
detects directly small-angle linear-response magnetic dynamics caused by spin
torque it is relatively immune to artifacts affecting competing techniques. At
high bias we find that the spin torque vector differs markedly from the simple
lowest-order Taylor series approximations commonly assumed.Comment: 29 pages, 5 figures including supplementary materia
Spectroscopic evidence for a charge-density-wave condensate in a charge-ordered manganite: Observation of collective excitation mode in PrCaMnO by using THz time-domain spectroscopy
THz time-domain spectroscopy was used to directly probe the low-energy
(0.5--5 meV) electrodynamics of the charge-ordered manganite
PrCaMnO. We revealed the existence of a finite peak
structure around 2--3 meV well below the charge gap meV. In analogy
to the low-energy optical properties of the well-studied low-dimensional
materials, we attributed this observed structure to the collective excitation
mode arising from the charge-density-wave condensate. This finding provides the
importance role of the quasi-one dimensional nature of the charge and orbital
ordering in PrCaMnO.Comment: REVTeX4, 8 pages including 7 figures and 2 table
Mixed-phase description of colossal magnetoresistive manganites
In view of recent experiments, indicating the spatial coexistence of
conducting and insulating regions in the ferromagnetic metallic phase of doped
manganites, we propose a refined mixed-phase description. The model is based on
the competition of a double-exchange driven metallic component and a polaronic
insulating component, whose volume fractions and carrier concentrations are
determined self-consistently by requiring equal pressure and chemical
potential. The resulting phase diagram as well as the order of the phase
transition are in very good agreement with measured data. In addition,
modelling the resistivity of the mixed, percolative phase by a random resistor
network, we obtain a pronounced negative magnetoresistance in the vicinity of
the Curie temperature .Comment: 7 pages, 6 figure
- …