Reena Mary, A P; Narayanan, T N; Vijutha, Sunny; Sakthikumar, D; Yasuhiko, Yoshida; Joy, P A; Anantharaman, M R(Springer, 2010)
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Abstract:
Bio-compatible magnetic fluids having high
saturation magnetization find immense applications in
various biomedical fields. Aqueous ferrofluids of superparamagnetic
iron oxide nanoparticles with narrow size
distribution, high shelf life and good stability is realized by
controlled chemical co-precipitation process. The crystal
structure is verified by X-ray diffraction technique. Particle
sizes are evaluated by employing Transmission electron
microscopy. Room temperature and low-temperature magnetic
measurements were carried out with Superconducting
Quantum Interference Device. The fluid exhibits good
magnetic response even at very high dilution (6.28 mg/cc).
This is an advantage for biomedical applications, since only
a small amount of iron is to be metabolised by body organs.
Magnetic field induced transmission measurements carried
out at photon energy of diode laser (670 nm) exhibited
excellent linear dichroism. Based on the structural and
magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of
radiofrequencies.
Swapna S, Nair; Rajesh, S; Abraham, V S; Anantharaman, M R(Springer, April , 2011)
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Abstract:
Ferrofluids belonging to the series, Ni x Fe1-x Fe2O4 and Zn x Fe1-x Fe2O4, were synthesized using cold co-precipitation. Liquid films of these ferrofluids were prepared by encapsulating the ferrofluids in between two optically smooth and ultrasonically cleaned glass plates. Magnetic field induced laser transmission through these ferrofluid films has been investigated. Magnetic field values can be calibrated in terms of output laser power in the low field region in which the variation is linear. This set up can be used as a cheap optical gaussmeter in the low field regime. Using the same set-up, the saturation magnetization of the sample used can also be calculated with a sample that is pre-characterized. Hence both magnetization of the sample, as well as applied magnetic field can be sensed and calculated with a precalibrated sample.
Senoy, Thomas; Sakthikumar, D; Yoshida, Yasuhiko; Anantharaman, M R(Springer, 2008)
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Abstract:
Sol–gel glasses with Fe3O4 nanoparticles having particle sizes laying in the range 10–20 nm were encapsulated
in the porous network of silica resulting in nanocomposites having both optical and magnetic
properties. Spectroscopic and photoluminescence studies indicated that Fe3O4 nanocrystals are embedded
in the silica matrix with no strong Si–O–Fe bonding. The composites exhibited a blue luminescence. The
optical absorption edge of the composites red shifted with increasing concentration of Fe3O4 in the silica
matrix. There is no obvious shift in the position of the luminescence peak with the concentration of Fe3O4
except that the intensity of the peak is decreased. The unique combinations of magnetic and optical
properties are appealing for magneto–optical applications.
Hysen, Thomas; Senoy, Thomas; Ramanujan, R V; Anantharaman, M R(Springer, 2008)
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Abstract:
Activation energy for crystallization (Ec) is a
pertinent parameter that decides the application potential of
many metallic glasses and is proportional to the crystallization
temperature. Higher crystallization temperatures are
desirable for soft magnetic applications, while lower values
for data storage purposes. In this investigation, from the
heating rate dependence of peak crystallization temperature
Tp, the Ec values have been evaluated by three different
methods for metglas 2826 MB (Fe40Ni38B18Mo4) accurately.
The Ec values are correlated with the morphological
changes, and the structural evolution associated with
annealing temperatures is discussed.
Shenoy, S D; Joy, P A; Anantharaman, M R(Elsevier, February , 2004)
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Abstract:
Nanosized ZnFe2O4 particles containing traces of a-Fe2O3 by intent were produced by low temperature chemical
coprecipitation methods. These particles were subjected to high-energy ball milling. These were then characterised using
X-ray diffraction, magnetisation and dielectric studies. The effect of milling on zinc ferrite particles have been studied
with a view to ascertaining the anomalous behaviour of these materials in the nanoregime. X-ray diffraction and
magnetisation studies carried out show that these particles are associated with strains and it is the surface effects that
contribute to the magnetisation. Hematite percentage, probably due to decomposition of zinc ferrite, increases with
milling. Dielectric behaviour of these particles is due to interfacial polarisation as proposed by Koops. Also the defects
caused by the milling produce traps in the surface layer contributes to dielectric permittivity via spin polarised electron
tunnelling between grains. The ionic mechanism is enhanced in dielectrics with the rise in temperature which results in
the increase of dielectric permittivity with temperature.
Anantharaman,M R; V P N Nampoori; Radhakrishnan,P; Girijavallabhan,C P; Sajan,D George; Saravanan, S; Venkatachalam,S(Physical Review, American Physical Society, June 8, 2004)
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Abstract:
Thermal diffusivity of the composites of camphor sulphonic acid (CSA) doped polyaniline (PANI) and its
composites with cobalt phthalocyanine (CoPc) has been measured using open cell photoacoustic technique.
Analysis of the data shows that the effective thermal diffusivity value can be tuned by varying the relative
volume fraction of the constituents. It is seen that polaron assisted heat transfer mechanism is dominant in CSA
doped PANI and these composites exhibit a thermal diffusivity value which is intermediate to that of CSA
doped PANI and CoPc. The results obtained are correlated with the electrical conductivity and hardness
measurements carried out on the samples