@article { ISI:000238329100003, title = {Effect of thermal annealing on Fe40Ni38B18Mo4 thin films: modified Herzer model for magnetic evolution}, journal = {Journal of Physics D-Applied Physics}, volume = {39}, number = {10}, year = {2006}, month = {MAY}, pages = {1993-2000}, publisher = {IOP PUBLISHING LTD}, type = {Article}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {

Magnetic properties of nano-crystalline soft magnetic alloys have usually been correlated to structural evolution with heat treatment. However, literature reports pertaining to the study of nano-crystalline thin films are less abundant. Thin films of Fe40Ni38B18Mo4 were deposited on glass substrates under a high vacuum of approximate to 10(-6) Torr by employing resistive heating. They were annealed at various temperatures ranging from 373 to 773K based on differential scanning calorimetric studies carried out on the ribbons. The magnetic characteristics were investigated using vibrating sample magnetometry. Morphological characterizations were carried out using atomic force microscopy (AFM), and magnetic force microscopy (MFM) imaging is used to study the domain characteristics. The variation of magnetic properties with thermal annealing is also investigated. From AFM and MFM images it can be inferred that the crystallization temperature of the as-prepared films are lower than their bulk counterparts. Also there is a progressive evolution of coercivity up to 573 K, which is an indication of the lowering of nano-crystallization temperature in thin films. The variation of coercivity with the structural evolution of the thin films with annealing is discussed and a plausible explanation is provided using the modified random anisotropy model.

}, issn = {0022-3727}, doi = {10.1088/0022-3727/39/10/002}, author = {Hysen, T. and Deepa, S. and Saravanan, S. and Ramanujan, R. V. and Avasthi, D. K. and Joy, Pattayil Alias and D Kulkarni, S. and Anantharaman, Maliemadom R.} } @article { ISI:000241157000039, title = {Evidence for intergranular tunnelling in polyaniline passivated alpha-Fe nanoparticles}, journal = {Nanotechnology}, volume = {17}, number = {18}, year = {2006}, month = {SEP}, pages = {4765-4772}, publisher = {IOP PUBLISHING LTD}, type = {Article}, address = {DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND}, abstract = {

Nanoparticles are of immense importance both from the fundamental and application points of view. They exhibit quantum size effects which are manifested in their improved magnetic and electric properties. Mechanical attrition by high energy ball milling (HEBM) is a top down process for producing fine particles. However, fineness is associated with high surface area and hence is prone to oxidation which has a detrimental effect on the useful properties of these materials. Passivation of nanoparticles is known to inhibit surface oxidation. At the same time, coating polymer film on inorganic materials modifies the surface properties drastically. In this work a modified set-up consisting of an RF plasma polymerization technique is employed to coat a thin layer of a polymer film on Fe nanoparticles produced by HEBM. Ball-milled particles having different particle size ranges are coated with polyaniline. Their electrical properties are investigated by measuring the dc conductivity in the temperature range 10-300 K. The low temperature dc conductivity (I-V) exhibited nonlinearity. This nonlinearity observed is explained on the basis of the critical path model. There is clear-cut evidence for the occurrence of intergranular tunnelling. The results are presented here in this paper.

}, issn = {0957-4484}, doi = {10.1088/0957-4484/17/18/039}, author = {Sunny, Vijutha and Narayanan, T. N. and Sajeev, U. S. and Joy, Pattayil Alias and Kumar, D. Sakthi and Yoshida, Yasuhiko and Anantharaman, Maliemadom R.} } @article { ISI:000254416300010, title = {Enhanced shape anisotropy and magneto-optical birefringence by high energy ball milling in NixFe1-xFe2O4 ferrofluids}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {320}, number = {6}, year = {2008}, month = {MAR}, pages = {815-820}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Ferrofluids belonging to the series NixFe1-xFe2O4 were synthesised by two different procedures-one by standard co-precipitation techniques, the other by co-precipitation for synthesis of particles and dispersion aided by high-energy ball milling with a view to understand the effect of strain and size anisotropy on the magneto-optical properties of ferrofluids. The birefringence measurements were carried out using a standard ellipsometer. The birefringence signal obtained for chemically synthesised samples was satisfactorily fitted to the standard second Langevin function. The ball-milled ferrofluids showed a deviation and their birefringence was enhanced by an order. This large enhancement in the birefringence value cannot be attributed to the increase in grain size of the samples, considering that the grain sizes of sample synthesised by both modes are comparable; instead, it can be attributed to the lattice strain-induced shape anisotropy(oblation) arising from the high-energy ball-milling process. Thus magnetic-optical (MO) signals can be tuned by ball-milling process, which can find potential applications. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {birefringence, Co-precipitation, ferrofluid, HEBM}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2007.08.032}, author = {Nair, Swapna S. and Xavier, Francis and Joy, Pattayil Alias and Kulkarni, S. D. and Anantharaman, Maliemadom R.} } @article { ISI:000269206600022, title = {Effect of nickel nanofillers on the dielectric and magnetic properties of composites based on rubber in the X-band}, journal = {Applied Physics A-Materials Science \& Processing}, volume = {97}, number = {1}, year = {2009}, month = {OCT}, pages = {157-165}, publisher = {SPRINGER}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Nickel-rubber nanocomposites were synthesized by incorporating ferromagnetic nickel nanoparticles in a natural rubber as well as neoprene rubber matrix. Complex dielectric permittivity and magnetic permeability of these composites were evaluated in the X-band microwave frequencies at room temperature using cavity perturbation technique. The dielectric loss in natural rubber is smaller compared to neoprene rubber. A steady increase in the dielectric permittivity is observed with increase in the content of nickel in both the composites. The magnetic permeability exhibits a steady decrease with increase in frequency and magnetic loss shows a relaxation at 8 GHz. The suitability of these composites as microwave absorbers is modeled based on the reflection loss which is dependant on the real and imaginary components of the complex dielectric permittivity and magnetic permeability.

}, issn = {0947-8396}, doi = {10.1007/s00339-009-5284-1}, author = {Jamal, E. Muhammad Abdul and Mohanan, P. and Joy, Pattayil Alias and Kurian, Philip and Anantharaman, Maliemadom R.} }