1,494 research outputs found
Interface driven magnetoelectric effects in granular CrO2
Antiferromagnetic and magnetoelectric Cr2O3-surfaces strongly affect the
electronic properties in half metallic CrO2. We show the presence of a Cr2O3
surface layer on CrO3 grains by high-resolution transmission electron
microscopy. The effect of these surface layers is demonstrated by measurements
of the temperature variation of the magnetoelectric susceptibility. A major
observation is a sign change at about 100 K followed by a monotonic rise as a
function of temperature. These electric field induced moments in CrO3 are
correlated with the magnetoelectric susceptibility of pure Cr2O3. This study
indicates that it is important to take into account the magnetoelectric
character of thin surface layers of Cr2O3 in granular CrO2 for better
understanding the transport mechanism in this system. The observation of a
finite magnetoelectric susceptibility near room temperature may find utility in
device applications.Comment: Figure 1 with strongly reduced resolutio
Probing a ferromagnetic critical regime using nonlinear susceptibility
The second order para-ferromagnetic phase transition in a series of amorphous
alloys (Fe{_5}Co{_{50}}Ni{_{17-x}}Cr{_x}B{_{16}}Si{_{12}}) is investigated
using nonlinear susceptibility. A simple molecular field treatment for the
critical region shows that the third order suceptibility (chi{_3}) diverges on
both sides of the transition temperature, and changes sign at T{_C}. This
critical behaviour is observed experimentally in this series of amorphous
ferromagnets, and the related assymptotic critical exponents are calculated. It
is shown that using the proper scaling equations, all the exponents necessary
for a complete characterization of the phase transition can be determined using
linear and nonlinear susceptiblity measurements alone. Using meticulous
nonlinear susceptibility measurements, it is shown that at times chi{_3} can be
more sensitive than the linear susceptibility (chi{_1}) in unravelling the
magnetism of ferromagnetic spin systems. A new technique for accurately
determining T{_C} is discussed, which makes use of the functional form of
chi{_3} in the critical region.Comment: 11 Figures, Submitted to Physical Review
A Brief Overview on Ferrite (Fe3O4) Based Polymeric Nanocomposites: Recent Developments and Challenges
In this article, we have mainly discussed about ferrite (Fe3O4) and its polymer based nanocomposites. Ferrite particles have become an important research material because of their vast applications in the field of biotechnology, magnetic resonance imaging (MRI), and data storage. It has been observed that ferrite Fe3O4 particles show best performance for size less than 10-30 nm. This happens due to the super paramagnetic nature of such particles. In super paramagnetic range these particles exhibit zero remanence or coercivity. Therefore, various properties of ferrite (Fe3O4) nanoparticles and its polymer nanocomposites are very much dependent on the size, and distribution of the particles in the polymeric matrix. Moreover, it has been also observed that the shape of the nanocrystals plays important role in the determination of their fundamental properties. These particles show instability over longer times due to the formation of agglomerates generated by high surface energies. Therefore, protection strategies such as grafting and coatings with silica/carbon or polymers have been developed to stabilize them chemically. Recently, silylation technique is mainly used for the modification of nanoparticles. Experimentally, it has been observed that nanocomposites composed of polymer matrices and ferrite showed substantial improvements in stiffness, fracture toughness, sensing ability (magnetic as well as electric), impact energy absorption, and electro-catalytic activities to bio-species
Development of a heating reactor for a continuous flow-through application in urea measurement
In most biochemical analyses, a flow-through heating arrangement is needed to reduce the reaction time or maintain a constant temperature. A rectangular reactor is described that is constructed of aluminium, is hollow inside and is filled with silicone oil. The glass coil through which the solution flows is immersed in the silicone oil. The heater, a Peltier-effect heat pump, on one side and the temperature sensor on the other side of the reactor body are embedded for heating and temperature control. The brief performance evaluation of the reactor is discussed by measuring the absorbance of urea concentration at different temperatures
Mathematical model for predicting solidification and cooling of steel inside mould and in air
A two-dimensional mathematical model has been developed to describe the solidification and cooling of steel inside the mould after teeming and in the air after stripping. Partial differential equations describing the processes have been discretized using control volume approach. The discretization equations obtained are of Tri-diagonal
matrix form, which have been solved using well known Tri-diagonal matrix algorithm (TDMA) and Alternate direction implicit (ADI) solver. The model has been validated by measuring surface temperatures of mould and ingot using Infrared thermo-vision scanner. This is then used to compute charging temperature and solidification status of
ingot as function of track time and type of ingot
A study of low level nitrogen laser therapy in the treatment of non-responding tubercular lymphadenopathy and sinuses
Forty-four cases of tubercular lymphadenopathy and sinuses, who were taking anti-tubercular treatment for more than 6 months and not responding to it, were randomly selected in this study. Overall cure rate in cases of lymphadenopathy was 93.99% , sinus 77.77% and cold abscess 100%. Mean age of the patients was 30.13 (Male: female1:4.5). Most common site of lymphadenopathy was cervical , smear was positive in 19(43.18%) cases and culture in 25(56.81%) cases. Low Level Nitrogen Laser Therapy may be used as an adjuvant to anti-tubercular drugs in cases of chronic non-responding tubercular lymphadenopathy and sinuses
Certain classes of univalent analitic functions
In the present paper we shall study the subclasses of starlike, convex, meromorphically starlike, and meromorphically  convex functions
Selective substitution in orbital domains of a low doped manganite : an investigation from Griffiths phenomenon and modification of glassy features
An effort is made to study the contrast in magnetic behavior resulting from
minimal disorder introduced by substitution of 2.5% Ga or Al in Mn-site of
LaSrMnO. It is considered that Ga or Al selectively
creates disorder within the orbital domains or on its walls, causing
enhancement of Griffiths phase (GP) singularity for the former and
disappearance of it in the later case. It is shown that Ga replaces Mn
which is considered to be concentrated within the domains, whereas Al replaces
Mn which is segregated on the hole-rich walls, without causing any
significant effect on structure or ferromagnetic transition temperatures. Thus,
it is presumed that the effect of disorder created by Ga extend across the bulk
of the domain having correlation over similar length-scale resulting in
enhancement of GP phenomenon. On the contrary, effect of disorder created by Al
remains restricted to the walls resulting in the modification of the dynamics
arising from the domain walls and suppresses the GP. Moreover contrasting
features are observed in the low temperature region of the compounds; a
re-entrant spin glass like behavior is observed in the Ga doped sample, while
the observed characteristics for the Al doped sample is ascribed only to
modified domain wall dynamics with the absence of any glassy phase. Distinctive
features in third order susceptibility measurements reveals that the magnetic
ground state of the entire series comprises of orbital domain states. These
observations bring out the role of the nature of disorder on GP phenomenon and
also reconfirms the character of self-organization in low-doped manganites
Morphometric analysis of Dactylorhiza hatagirea (D. Don), a critically endangered orchid in cold desert Ladakh region of India
The morphometric study was conducted during 2009 to 2010. About 28 morphological characters were measured under 13 natural populations of Dactylorhiza hatagirea. Geographic variation in morphology reflects phenotypic responses to environmental gradients and evolutionary history of populations and species. At points, beside its broad geographic range (Nubra, Suru and Indus valley) characterization of Dactylorhiza phenotype is normally accomplished by use of morphological descriptors, hence as a first step, phenotype collection and its morphometric analysis was assessed. However, plant height, leaf length, lowermost leaf length, length of second leaf from base and mean length from lowest bract to the top of inflorescence are presented to account for the remarkable variation in morphological characters. Tirith population showed more values of this trait while Skurru showed less value. From this, it is concluded that Tirith showed great morphometric variation as compared to other population. Multivariate morphometric techniques, principal component analysis (PCA), multidimensional scaling (MDS) and cluster analysis were used to determine whether these populations can be reliably morphologically similar or dissimilar. The first two principal components encompass more than 75% variation among population. The results of PCA and MDS analysis were comparable to the cluster analysis, which shows considerable phenotypic variation in morphological and horticultural traits that can be utilized in its genetic improvement. To support this study, further constructive information were provided on the status of the populations of D. hatagirea which may increase the conservation value of this site and resolve the suitable areas with taxonomic and nomenclatural controversies.Keywords: Morphological characters, principal component analysis (PCA), multidimensional scaling (MDS), plant height, leaf length, leaf widt
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