Anantharaman, M R; Sethulakshmi, N; Al-Omari, I A; Suresh, K G(AIP Publishing, March 5, 2014)
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Abstract:
Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent
ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering
at 300K and the magnetic isotherms at different temperature ranges were analyzed for estimating
magnetic entropy variation. Magnetic entropy change of 1.5 J kg 1 K 1 was observed near 300 K.
An appreciable magnetocaloric effect was also observed for a wide range of temperatures near
300K for small magnetic field variation. Heat capacity was measured for temperatures lower than
300K and the adiabatic temperature change increases with increase in temperature with a
maximum of 0.62K at 280 K
Anantharaman, M R; Lisha, R; Hysen, T; Geetha, P; Avasthi, D K; Ramanujan, R V(IOP Publishing LTD, March 7, 2014)
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Abstract:
Metglas 2826 MB having a nominal composition of Fe40Ni38Mo4B18 is an
excellent soft magnetic material and finds application in sensors and memory
heads. However, the thin-film forms of Fe40Ni38Mo4B18 are seldom studied,
although they are important in micro-electro-mechanical systems/nano-electromechanical
systems devices. The stoichiometry of the film plays a vital role in
determining the structural and magnetic properties of Fe40Ni38Mo4B18 thin
films: retaining the composition in thin films is a challenge. Thin films of 52 nm
thickness were fabricated by RF sputtering technique on silicon substrate from a
target of nominal composition of Fe40Ni38Mo4B18. The films were annealed at
temperatures of 400 °C and 600 °C. The micro-structural studies of films using
glancing x-ray diffractometer (GXRD) and transmission electron microscope
(TEM) revealed that pristine films are crystalline with (FeNiMo)23B6 phase.
Atomic force microscope (AFM) images were subjected to power spectral
density analysis to understand the probable surface evolution mechanism during
sputtering and annealing. X-ray photoelectron spectroscopy (XPS) was
employed to determine the film composition. The sluggish growth of crystallites
with annealing is attributed to the presence of molybdenum in the thin film. The
observed changes in magnetic properties were correlated with annealing induced
structural, compositional and morphological changes
Anantharaman, M R; Lija, Joy K; Sooraj, V; Swapna, Nair S; Narayanan, T N; Ajayan, P M; Sethulakshmi, N(AIP Publishing, March 28, 2014)
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Abstract:
Commercial samples of Magnetite with size ranging from 25–30nm were coated with polyaniline by
using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle
(core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core
shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were
studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large
dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a
Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric
permittivity is proposed
Anantharaman, M R; Vinayasree, S; Soloman, M A; Vijutha, Sunny; Mohanan, P; Joy, P A; Philip, Kurian(AIP Publishing, July 9, 2014)
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Abstract:
Flexile single layer electromagnetic wave absorbers were designed by incorporating appropriate
amounts of carbon black in a nitrile butadiene rubber matrix along with an optimized amount of
magnetic counterpart, namely, barium hexaferrite for applications in S, C, and X-bands. Effective
dielectric permittivity and magnetic permeability were measured using cavity perturbation method
in the frequency range of 2–12 GHz. The microwave absorbing characteristics of the composites
were studied in the S, C, and X-bands employing a model in which an electromagnetic wave is
incident normally on a metal terminated single layer. Reflection loss exceeding 20 dB is obtained
for all the samples in a wide frequency range of 2–12 GHz when an appropriate absorber thickness
between 5 and 9mm is chosen. The impact of carbon black is clearly observed in the optimized
composites on the mechanical strength, thickness, band width of absorption, dielectric properties,