1,243 research outputs found
Magnetic properties of Hydrogenated Li and Co doped ZnO nanoparticles
The effect of hydrogenation on magnetic properties of Zn0.85Co0.05Li0.10O
nanoparticles is presented. It was found that the sample hydrided at room
temperature (RT) showed weak ferromagnetism (FM) while that hydrided at 400oC
showed robust ferromagnetism at room temperature. In both cases reheating the
sample at 400oC in air converts it back into paramagnetic state (P) completely.
The characterization of samples by X-ray and electron diffraction (ED) showed
that room temperature ferromagnetism observed in the samples hydrogenated at RT
is intrinsic in nature whereas that observed in the samples hydrogenated at
400oC is partly due to the cobalt metal clusters.Comment: 10 pages, 3 figure
Influence of system parameters on the hysteresis characteristics of a horizontal Rijke tube
The influence of system parameters such as heater power, heater location and mass flow rate on the hysteresis characteristics of a horizontal Rijke tube is presented in this paper. It is observed that a hysteresis zone is present for all the mass flow rates considered in the present study. A power law relation is established between the non-dimensional hysteresis width and the Strouhal number, defined as the ratio between convective time scale and acoustic time scale. The transition to instability in a horizontal Rijke tube is found to be subcritical in all the experiments performed in this study. When heater location is chosen as the control parameter, period-2 oscillations are found for specific values of mass flow rate and heater power
Strong clustering of non-interacting, passive sliders driven by a Kardar-Parisi-Zhang surface
We study the clustering of passive, non-interacting particles moving under
the influence of a fluctuating field and random noise, in one dimension. The
fluctuating field in our case is provided by a surface governed by the
Kardar-Parisi-Zhang (KPZ) equation and the sliding particles follow the local
surface slope. As the KPZ equation can be mapped to the noisy Burgers equation,
the problem translates to that of passive scalars in a Burgers fluid. We study
the case of particles moving in the same direction as the surface, equivalent
to advection in fluid language. Monte-Carlo simulations on a discrete lattice
model reveal extreme clustering of the passive particles. The resulting Strong
Clustering State is defined using the scaling properties of the two point
density-density correlation function. Our simulations show that the state is
robust against changing the ratio of update speeds of the surface and
particles. In the equilibrium limit of a stationary surface and finite noise,
one obtains the Sinai model for random walkers on a random landscape. In this
limit, we obtain analytic results which allow closed form expressions to be
found for the quantities of interest. Surprisingly, these results for the
equilibrium problem show good agreement with the results in the non-equilibrium
regime.Comment: 14 pages, 9 figure
Room temperature Ferromagnetism in Th1-xFexO2-d (x = 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) nanoparticles
Nanocrystalline (Th1-xFex)O2-d particles with different Fe concentrations (x
= 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) have been prepared by a gel combustion
method. Rietveld refinement analyses of X-ray diffraction data revealed the
formation of an impurity free cubic type Th1-xFexO2-d structure up to x = 0.20.
This observation is further confirmed from the detailed studies conducted on 10
at. percent Fe doped ThO2 using high-resolution transmission electron
microscopy (HRTEM) imaging and indexing of the selected-area electron
diffraction (SAED) patterns. DC Magnetization studies as a function field
indicate that they are ferromagnetic with Curie temperature (Tc) well above
room temperature.Comment: 10 pages, 5 figure
Theory of Transition Temperature of Magnetic Double Perovskites
We formulate a theory of double perovskite coumpounds such as SrFeReO
and SrFeMoO which have attracted recent attention for their possible
uses as spin valves and sources of spin polarized electrons. We solve the
theory in the dynamical mean field approximation to find the magnetic
transition temperature . We find that is determined by a subtle
interplay between carrier density and the Fe-Mo/Re site energy difference, and
that the non-Fe same-sublattice hopping acts to reduce . Our results
suggest that presently existing materials do not optimize
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