1,376 research outputs found
Preparation of high crystalline nanoparticles of rare-earth based complex pervoskites and comparison of their structural and magnetic properties with bulk counterparts
A simple route to prepare GdSrMnO nanoparticles by
ultrasonication of their bulk powder materials is presented in this article.
For comparison, GdSrMnO nanoparticles are also prepared by
ball milling. The prepared samples are characterized by X-ray diffraction
(XRD),field emission scanning electron microscope (FESEM), energy dispersive
X-ray (EDX), X-ray photoelectron spectroscope (XPS), and Superconducting
Quantum Interference Device (SQUID) magnetometer. XRD Rietveld analysis is
carried out extensively for the determination of crystallographic parameters
and the amount of crystalline and amorphous phases. FESEM images demonstrate
the formation of nanoparticles with average particle size in the range of
50-100 nm for both ultrasonication and 4 hours (h) of ball milling. The bulk
materials and nanoparticles synthesized by both ultrasonication and 4 h ball
milling exhibit a paramagnetic to spin-glass transition. However, nanoparticles
synthesized by 8 h and 12 h ball milling do not reveal any phase transition,
rather show an upturn of magnetization at low temperature. The degradation of
the magnetic properties in ball milled nanoparticles may be associated with
amorphization of the nanoparticles due to ball milling particularly for milling
time exceeding 8 h. This investigation demonstrates the potential of
ultrasonication as a simple route to prepare high crystalline rare-earth based
manganite nanoparticles with improved control compared to the traditional ball
milling technique.Comment: 9 pages, 6 figure
Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO
Improvement in magnetic and electrical properties of multiferroic BiFeO
in conjunction with their dependence on particle size is crucial due to its
potential applications in multifunctional miniaturized devices. In this
investigation, we report a study on particle size dependent structural,
magnetic and electrical properties of sol-gel derived
BiBaFeO nanoparticles of different sizes ranging from
12 to 49 nm. The substitution of Bi by Ba significantly suppresses
oxygen vacancies, reduces leakage current density and Fe state. An
improvement in both magnetic and electrical properties is observed for 10 %
Ba-doped BiFeO nanoparticles compared to its undoped counterpart. The
saturation magnetization of BiBaFeO nanoparticles increase
with reducing particle size in contrast with a decreasing trend of
ferroelectric polarization. Moreover, a first order metamagnetic transition is
noticed for 49 nm BiBaFeO nanoparticles which
disappeared with decreasing particle size. The observed strong size dependent
multiferroic properties are attributed to the complex interaction between
vacancy induced crystallographic defects, multiple valence states of Fe,
uncompensated surface spins, crystallographic distortion and suppression of
spiral spin cycloid of BiFeO.Comment:
Fluctuating Flow of Thermomicropolar Fluid Past a Vertical Surface
The unsteady free convection boundary layer flow of a thermo-micropolar fluid along a vertical plate has been investigated in this paper. The temperature of the plate is assumed to be oscillating about a mean temperature, θw(x), with small amplitude ε. The governing boundary layer equations are analyzed using straight forward finite difference method. The effects of the material parameters such as micropolar heat conduction parameter, N*, the vortex viscosity parameter, K, on the shear stress,w, surface heat transfer, qw, and the couple-stress, mw, have been investigated
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