@article { ISI:000260776800023, title = {Superparamagnetic nanocrystalline ZnFe2O4 with a very high curie temperature}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {8}, number = {8}, year = {2008}, month = {AUG}, pages = {3955-3958}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USA}, abstract = {

Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as similar to 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

}, keywords = {Curie temperature, Nanocrystalline, Superparamagnetism, Zinc Ferrite}, issn = {1533-4880}, doi = {10.1166/jnn.2008.201}, author = {Deka, Sasanka and Joy, Pattayil Alias} } @article { ISI:000207804200008, title = {Single step synthesis and properties of M/MFe2O4 and PVDF/M/MFe2O4 (M = Co, Ni) magnetic nanocomposites}, journal = {Science of Advanced Materials}, volume = {1}, number = {3}, year = {2009}, month = {DEC}, pages = {262-268}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {

Metal/ferrite nanocomposites (M/MFe2O4; M = Co, Ni), consisting of nanoparticles of a metal and the corresponding metal ferrite, have been synthesized under in situ conditions by a simple and single step process. The metal/ferrite nanocomposites embedded in a polymer matrix have been prepared by a simple hot-pressing method. The performance parameters such as magnetization, coercivity, permeability and dielectric constant of the two- and three-phase nanocomposite systems are compared. The coercivity increases and the permeability decreases with increasing polymer content in the three-phase composite. Enhancement of the dielectric constant is observed at low frequencies.

}, keywords = {Dielectric, Ferrite, magnetic properties, Nanocomposite, Nanocrystalline, permeability}, issn = {1947-2935}, doi = {10.1166/sam.2009.1053}, author = {Deka, Sasanka and Joy, Pattayil Alias and Kumar, A. Pratheep} } @article { ISI:000313149800004, title = {Enhancement in the magnetostriction of sintered cobalt ferrite by making self-composites from nanocrystalline and bulk powders}, journal = {ACS Applied Materials \& Interfaces}, volume = {4}, number = {12}, year = {2012}, month = {DEC}, pages = {6421-6425}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Sintered polycrystalline cobalt ferrite is a potential magnetostrictive smart material for applications as sensors and actuators. A novel concept of enhancing the magnetostrictive strain of sintered cobalt ferrite by making self-composites from nanosized and bulk powders with different particle sizes of the same material as components is reported. The self-composites give higher magnetostriction coefficient and strain derivative when compared to the sintered products obtained from the individual powders. The individual components give a maximum magnetostriction up to similar to 310 ppm, whereas up to similar to 370 ppm is obtained for a two-component system consisting of powders of two different sizes. On the other hand, a three-component self-composite made from starting powders of 3 nm, 40 nm and \>1 mu m give very high magnetostriction of similar to 400 ppm at 800 kA/m, suitable for making devices.

}, keywords = {Cobalt ferrite, Magnetostriction, Nanocrystalline, self-composite, Sintering}, issn = {1944-8244}, doi = {10.1021/am302053q}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000324099300024, title = {High magnetostriction coefficient of Mn substituted cobalt ferrite sintered from nanocrystalline powders and after magnetic field annealing}, journal = {Current Applied Physics}, volume = {13}, number = {8}, year = {2013}, month = {OCT}, pages = {1697-1701}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Magnetostriction characteristics of Mn substituted cobalt ferrite, CoFe2-xMnxO4 (0 \<= x \<= 0.3), sintered from nanocrystalline powders of average particle size of similar to 4 nm have been studied. Larger value of magnetostriction at lower magnetic field is achieved after substitution of Mn for Fe. The maximum value of magnetostriction coefficient is not much affected and the slope of the magnetostriction is increased with increasing Mn content. Higher maximum value of magnetostriction coefficient (lambda) of 234 ppm comparable to that of the unsubstituted composition with larger strain derivative (d lambda/dH) is obtained for x = 0.2 in CoFe2-xMnxO4. The magnetostriction coefficient is increased to 262 ppm with further enhancement in the strain derivative after annealing the sintered compact at 300 degrees C in a magnetic field of 400 kA/m for 30 min. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetic field annealing, Magnetostriction, Mn substitution, Nanocrystalline}, issn = {1567-1739}, doi = {10.1016/j.cap.2013.06.030}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000324311200017, title = {Influence of initial particle size on the magnetostriction of sintered cobalt ferrite derived from nanocrystalline powders}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {346}, year = {2013}, month = {NOV}, pages = {96-102}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The role of initial particle size on the magnetostriction coefficient of sintered cobalt ferrite derived from nanocrystalline powders is studied. Nanoparticles of cobalt ferrite with different sizes in the range 3-80 nm are synthesized by an autocombustion method using metal nitrates and glycine. It has been observed that the initial particle size of the starting powders has a strong influence on the magnetostrictive behavior of sintered cobalt ferrite. Highest magnetostrictive strain and strain derivative are obtained for sintered ferrite derived from nanoparticles of size \< 5 nm. The results show that higher magnetostriction coefficient for sintered cobalt ferrite can be achieved by compacting nanocrystalline particles of very small size. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt ferrite, magnetic properties, Magnetostriction, Microstructure, Nanocrystalline, Particle size}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2013.07.016}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000329554400013, title = {Studies on the effect of sintering conditions on the magnetostriction characteristics of cobalt ferrite derived from nanocrystalline powders}, journal = {Journal of the European Ceramic Society}, volume = {34}, number = {3}, year = {2014}, month = {MAR}, pages = {677-686}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

The effect of sintering conditions on the magnetostriction characteristics of sintered cobalt ferrite derived from nanocrystalline powders is studied. It is observed that the magnetostriction coefficient as well as the slope of the magnetostriction as a function of field depends on the microstructure of the sintered product. There is a direct correlation between the magnetostriction characteristics and density as well as porosity of the sintered products. Intragranular pores are found to be strongly influencing the magnetostriction characteristics. Similarly, correlation is found between the magnetostriction parameters and the Curie temperature, indicating the role of cation distribution which affects the magnetic anisotropy. Sintering the compacts made from nanocrystalline powders at 1450 degrees C for a very short duration is found to give high values of magnetostriction coefficient. However, higher values of magnetostriction at low magnetic fields are obtained for samples sintered at lower temperatures for longer duration and having relatively lower density. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetostriction, Microstructure, Nanocrystalline, Sintering}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2013.09.018}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} }