| Abstract: | The development of methods to economically synthesize single wire structured multiferroic systems with room temperature spin−charge coupling is expected to be important for building next-generation multifunctional devices with ultralow power consumption. We demonstrate the fabrication of a single nanowire multiferroic system, a new geometry, exhibiting room temperature magnetodielectric coupling. A coaxial nanotube/nanowire heterostructure of barium titanate (BaTiO3, BTO) and cobalt (Co) has been synthesized using a template-assisted method. Room temperature ferromagnetism and ferroelectricity were exhibited by this coaxial system, indicating the coexistence of more than one ferroic interaction in this composite system |
| Description: | Nano Lett. 2012, 12, 3025−3030 |
| URI: | http://dyuthi.cusat.ac.in/purl/4376 |
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| Hybrid Multifer ... tic−DielectricCoupling.pdf | (1.242Mb) |
| Abstract: | Mn1-xZnxFe2O4 nanoparticles (x=0-1) were synthesized by wet chemical co-precipitation techniques. X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy were effectively utilized to investigate the different structural parameters. The elemental analysis was conducted using energy-dispersive spectrum and inductively coupled plasma analysis. The magnetic properties such as magnetization and coercivity were measured using vibrating sample magnetometer. The observed magnetization values of the nanoparticles were found to be lower compared to the bulk counterpart. The magnetization showed a gradual decrease with zinc substitution except for a small increase from x=0.2 to 0.3. The Curie temperature was found to be enhanced in the case of ferrites in the nanoregime. The variation in lattice constant, reduced magnetization values, variation of magnetization with zinc substitution, the presence of a net magnetic moment for the zinc ferrite and the enhancement in Curie temperature in Mn1-xZnxFe2O4 all provide evidence to the existence of a metastable cation distribution together with possible surface effects at the nanoregime. |
| URI: | http://dyuthi.cusat.ac.in/purl/2833 |
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| Dyuthi-P00389.pdf | (1.422Mb) |
| Abstract: | Preparatiun or aci cular maghemi te containing dopan ls li ke Mg. i and Gd and their characleris,llion us ing different analytica l techniques have been reported. These in vestigat ions reveal that the addition of dopants li ke Mg. Ni and Gd modifies the magnetic properties without cfrecting any structural changes. The opt ical bandgaps of these doped compositions have ,li S() hecn determ ined. Evidence is ,li so av,li lab le from spectroscopic investi gations suggest ing thalmaghcllli te prepared vi,l the ()xa l,ltc precursor route does nm exhi bit a hydrogen fe rrite structure |
| Description: | Ind ian Joum,ll of Pure & Applied Phys ics Vol. 37. November 1999. pr. 842-847 |
| URI: | http://dyuthi.cusat.ac.in/purl/4435 |
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| Influence of do ... roperties of maghemite.pdf | (1.171Mb) |
| Abstract: | We investigated the influence of substrate surface roughness on the structural and magnetic properties of obliquely deposited amorphous nanocolumns of Fe–Ni. Experiments showed that the surface roughness of the substrate greatly determines the morphology of the columnar structures and this in turn has a profound influence on the magnetic properties. Nucleation of Fe–Ni nanocolumns on a smooth silicon substrate was at random, while that on a rough glass substrate was defined by the irregularities on the substrate surface. It has been found that magnetic interaction between the nanocolumns prepared on a silicon substrate was due to their small inter-column separation. Well separated nanocolumns on a glass substrate resulted in exchange isolated magnetic domains. The size, shape and the distribution of nanocolumns can be tailored by appropriately choosing the surface roughness of the substrate. This will find potential applications in thin film magnetism. |
| Description: | J. Phys. D: Appl. Phys. 42 (2009) 215005 (8pp) |
| URI: | http://dyuthi.cusat.ac.in/purl/4405 |
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| Influence of su ... s nanocolumns of Fe–Ni.pdf | (1.327Mb) |
| Abstract: | The magnetocaloric properties of cobalt ferrite nanoparticles were investigated to evaluate the potential of these materials as magnetic refrigerants. Nanosized cobalt ferrites were synthesized by the method of sol–gel combustion. The nanoparticles were found to be spherical with an average crystallite size of 14 nm. The magnetic entropy change ( Sm) calculated indirectly from magnetization isotherms in the temperature region 170–320 K was found to be negative, signifying an inverse magnetocaloric effect in the nanoparticles. The magnitudes of the Sm values were found to be larger when compared to the reported values in the literature for the corresponding ferrite materials in the nanoregime. |
| Description: | Appl Phys A (2010) 99: 497–503 |
| URI: | http://dyuthi.cusat.ac.in/purl/4365 |
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| Inverse magneto ... rived nanosized cobalt.pdf | (807.0Kb) |
| Abstract: | Polyaniline is chemically synthesised and doped with camphor sulphonic acid. FTIR studies carried out on these samples indicate that the aromatic rings are retained after polymerisation. The percentage of crystallinity for polyaniline doped with camphor sulphonic acid has been estimated from the X-ray diffraction studies and is around 56% with respect to polyaniline emeraldine base. The change in dielectric permittivity with respect to temperature and frequency is explained on the basis of interfacial polarisation. AC conductivity is evaluated from the observed dielectric permittivity. The values of AC and DC conductivity and activation energy are calculated. The activation energy values suggested that the hopping conduction is the prominent conduction mechanism in this system. |
| Description: | Journal of Physics and Chemistry of Solids 67 (2006) 1496–1501 |
| URI: | http://dyuthi.cusat.ac.in/purl/4359 |
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| Investigations ... camphor sulphonic acid.pdf | (360.4Kb) |
| Abstract: | Plasma polymerization is found to be an excellent technique for the preparation of good quality, pinhole-free, polymer thin films from different monomer precursors. The present work describes the preparation and characterization of polypyrrole (PPy) thin films by ac plasma polymerization technique in their pristine and in situ iodine doped forms. The electrical conductivity studies of the aluminiumpolymeraluminium (AlpolymerAl) structures have been carried out and a space charge limited conduction (SCLC) mechanism is identified as the most probable mechanism of carrier transport in these polymer films. The electrical conductivity shows an enhanced value in the iodine doped sample. The reduction of optical band gap by iodine doping is correlated with the observed conductivity results. |
| URI: | http://dyuthi.cusat.ac.in/purl/2835 |
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| Dyuthi-P00391.pdf | (582.5Kb) |
| 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 |
| Description: | Applied Physics Letters 104, 121603 (2014) |
| URI: | http://dyuthi.cusat.ac.in/purl/4421 |
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| Large enhanced ... plasma polymerization.pdf | (1.105Mb) |
| Abstract: | Lead free magneto electrics with a strong sub resonant (broad frequency range) magneto electric coupling coefficient (MECC) is the goal of the day which can revolutionise the microelectronics and microelectromechanical systems (MEMS) industry. We report giant resonant MECC in lead free nanograined Barium Titanate–CoFe (Alloy)-Barium Titanate [BTO-CoFe-BTO] sandwiched thin films. The resonant MECC values obtained here are the highest values recorded in thin films/ multilayers. Sub-resonant MECC values are quite comparable to the highest MECC reported in 2-2 layered structures. MECC got enhanced by two orders at a low frequency resonance. The results show the potential of these thin films for transducer, magnetic field assisted energy harvesters, switching devices, and storage applications. Some possible device integration techniques are also discussed |
| Description: | JOURNAL OF APPLIED PHYSICS 114, 064309 (2013) |
| URI: | http://dyuthi.cusat.ac.in/purl/4430 |
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| Lead free heter ... l systems applications.pdf | (2.457Mb) |
| Abstract: | Composite magnetic materials have the unique advantage of property modification for tailoring devices for various applications. Rubber ferrite composites (RFCs) prepared by incorporating ferrites in rubber matrixes have the advantage of easy mouldability and flexibility. RFCs containing various loadings of nickel zinc ferrite (NZF) (Ni1 xZnxFe2O4) in a natural rubber matrix have been prepared. The cure characteristics and the mechanical properties of these composites were evaluated. The effect of loading on the cure characteristics and tensile properties were also evaluated. It is found that the loading dependence on the cure time and mechanical properties exhibit an identical pattern. |
| URI: | http://dyuthi.cusat.ac.in/purl/2830 |
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| Dyuthi-P00386.pdf | (204.2Kb) |
| Abstract: | A series of vanadium-niobium oxide catalysts in which the vanadia content varies between 0.3 and 18mol%was prepared by coprecipitation. These catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low-energy ion scattering (LEIS), and by catalytic testing in the oxidative dehydrogenation reaction of propane. The results of the surface analysis by XPS and LEIS are compared. It is concluded that the active site on the catalyst surface contains 2.0 ± 0.3 vanadium atoms on average. This can be understood byassuming the existenceof two or three different sites:isolated vanadium atoms, pairs of vanadium atoms, or ensembles of three vanadium atoms. At higher vanadium concentration more vanadium clusters with a higher activity are at the surface.LEIS revealed that as the vanadium concentration in the catalyst increases, vanadium replaces niobium at the surface. At vanadium concentrations above 8 mol%, new phases such as P-(Nb, V)20S which are less active because vanadium is present in isolated sites are formed, while the vanadium surface concentration shows a slight decrease |
| Description: | JOURNAL OF CATALYSIS 157,584-591 (1995) |
| URI: | http://dyuthi.cusat.ac.in/purl/4356 |
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| A Low-Energy Io ... drogenation of Propane.pdf | (710.3Kb) |
| Abstract: | Thermally stable materials with low dielectric constant (k < 3.9) are being hotly pursued. They are essential as interlayer dielectrics/intermetal dielectrics in integrated circuit technology, which reduces parasitic capacitance and decreases the RC time constant. Most of the currently employed materials are based on silicon. Low k films based on organic polymers are supposed to be a viable alternative as they are easily processable and can be synthesized with simpler techniques. It is known that the employment of ac/rf plasma polymerization yields good quality organic thin films, which are homogenous, pinhole free and thermally stable. These polymer thin films are potential candidates for fabricating Schottky devices, storage batteries, LEDs, sensors, super capacitors and for EMI shielding. Recently, great efforts have been made in finding alternative methods to prepare low dielectric constant thin films in place of silicon-based materials. Polyaniline thin films were prepared by employing an rf plasma polymerization technique. Capacitance, dielectric loss, dielectric constant and ac conductivity were evaluated in the frequency range 100 Hz– 1 MHz. Capacitance and dielectric loss decrease with increase of frequency and increase with increase of temperature. This type of behaviour was found to be in good agreement with an existing model. The ac conductivity was calculated from the observed dielectric constant and is explained based on the Austin–Mott model for hopping conduction. These films exhibit low dielectric constant values, which are stable over a wide range of frequencies and are probable candidates for low k applications. |
| Description: | New Journal of Physics 6 (2004) 64 |
| URI: | http://dyuthi.cusat.ac.in/purl/4360 |
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| Low k thin film ... ma-polymerized aniline.pdf | (388.1Kb) |
| Abstract: | Nanocomposites with magnetic components possessing nanometric dimensions, lying in the range 1–10 nm, are found to be exhibiting superior physical properties with respect to their coarser sized counterparts. Magnetic nanocomposites based on gamma iron oxide embedded in a polymer matrix have been prepared and characterized. The behaviour of these samples at low temperatures have been studied using Mössbauer spectroscopy. Mössbauer studies indicate that the composites consist of very fine particles of g-Fe2O3 of which some amount exists in the superparamagnetic phase. The cycling of the preparative conditions were found to increase the amount of g-Fe2O3 in the matrix |
| Description: | Bull. Mater. Sci., Vol. 27, No. 4, August 2004, pp. 361–366 |
| URI: | http://dyuthi.cusat.ac.in/purl/4394 |
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| Low temperature ... agnetic nanocomposites.pdf | (284.6Kb) |
| Abstract: | Fine particles of barium ferrite (BaFe12O19) belonging to the M-type hexagonal ferrites were prepared by the conventional ceramic techniques. They were incorporated into a nitrile rubber matrix according to a specific recipe for various loadings to produce rubber ferrite composites (RFC). The percolation threshold is not reached for a maximum loading of 130 phr (parts per hundred rubber). Here in this paper, the magnetic properties and processability of the nitrile rubber based RFCs containing barium ferrite (BaF) and HAF carbon black is reported. The magnetic properties of the ceramic ferrite and these rubber ferrite composites were evaluated and it was found that the coercivity values of RFCs were less than that of the ceramic BaF, but remained constant with the loading of both the ferrite filler and carbon black. However, other properties like saturation magnetization and magnetic remanence increased with the loading of ferrite filler. |
| Description: | Indian Journal of Chemical Technology Vol. 12, September 2005, pp. 582-587 |
| URI: | http://dyuthi.cusat.ac.in/purl/4417 |
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| Magnetic and pr ... rrite and carbon black.pdf | (209.6Kb) |
| Abstract: | Polycrystalline single phasic mixed ferrites belonging to the series Ni1−xZnxFe2O4 for various values of x have been prepared by conventional ceramic techniques. Pre-characterized nickel zinc ferrites were then incorporated into a natural rubber matrix according to a specific recipe for various loadings. The processability and cure parameters were then determined. The magnetic properties of the ceramic filler as well as the ferrite loaded rubber ferrite composites (RFC) were evaluated and compared. A general equation for predicting the magnetic properties was also formulated. The validity of these equations were then checked and correlated with the experimental data. The coercivity of the RFCs almost resemble that of the ceramic component in the RFC. Percolation threshold is not reached for a maximum loading of 120 phr (parts per hundred rubber by weight) of the filler. These studies indicate that flexible magnets can be made with appropriate magnetic properties namely saturation magnetisation (Ms) and magnetic field strength (Hc) by a judicious choice of x and a corresponding loading. These studies also suggest that there is no possible interaction between the filler and the matrix at least at the macroscopic level. The formulated equation will aid in synthesizing RFCs with predetermined magnetic |
| Description: | JOURNAL OF MATERIALS SCIENCE 36 (2001) 5551 – 5557 |
| URI: | http://dyuthi.cusat.ac.in/purl/4358 |
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| Magnetic and pr ... bber and mixed ferrite.pdf | (144.6Kb) |
| Abstract: | We have investigated the effects of swift heavy ion irradiation on thermally evaporated 44 nm thick, amorphous Co77Fe23 thin films on silicon substrates using 100 MeV Ag7+ ions fluences of 1 1011 ions/ cm2, 1 1012 ions/cm2, 1 1013 ions/cm2, and 3 1013 ions/cm2. The structural modifications upon swift heavy irradiation were investigated using glancing angle X-ray diffraction. The surface morphological evolution of thin film with irradiation was studied using Atomic Force Microscopy. Power spectral density analysis was used to correlate the roughness variation with structural modifications investigated using X-ray diffraction. Magnetic measurements were carried out using vibrating sample magnetometry and the observed variation in coercivity of the irradiated films is explained on the basis of stress relaxation. Magnetic force microscopy images are subjected to analysis using the scanning probe image processor software. These results are in agreement with the results obtained using vibrating sample magnetometry. The magnetic and structural properties are correlated |
| Description: | Nuclear Instruments and Methods in Physics Research B 310 (2013) 81–86 |
| URI: | http://dyuthi.cusat.ac.in/purl/4423 |
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| Magnetic and to ... y Ag7+ ion irradiation.pdf | (1.990Mb) |
| Abstract: | Fine magnetic particles (sizeffi100A ˚ ) belonging to the series ZnxFe1 xFe2O4 were synthesized by cold co-precipitation methods and their structural properties were evaluated using X-ray diffraction. Magnetization studies have been carried out using vibrating sample magnetometry (VSM) showing near-zero loss loop characteristics. Ferrofluids were then prepared employing these fine magnetic powders using oleic acid as surfactant and kerosene as carrier liquid by modifying the usually reported synthesis technique in order to induce anisotropy and enhance the magneto-optical signals. Liquid thin films of these fluids were prepared and field-induced laser transmission through these films was studied. The transmitted light intensity decreases at the centre with applied magnetic field in a linear fashion when subjected to low magnetic fields and saturate at higher fields. This is in accordance with the saturation in cluster formation. The pattern exhibited by these films in the presence of different magnetic fields was observed with the help of a CCD camera and was recorded photographically |
| Description: | Journal of Magnetism and Magnetic Materials 305 (2006) 28–34 |
| URI: | http://dyuthi.cusat.ac.in/purl/4403 |
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| Magnetic field- ... ubstituted ferrofluids.pdf | (290.9Kb) |
| Abstract: | Mn1−xZnxFe2O4 nanoparticles (x = 0 to 1) were synthesized by the wet chemical co-precipitation technique. X-ray diffraction and transmission electron microscopy and high resolution transmission electron microscopy were effectively utilized to investigate the different structural parameters. The ac conductivity of nanosized Mn1−xZnxFe2O4 were investigated as a function of frequency, temperature and composition. The frequency dependence of ac conductivity is analysed by the power law σ(ω)ac = Bωn which is typical for charge transport by hopping or tunnelling processes. The temperature dependence of frequency exponent n was investigated to understand the conduction mechanism in different compositions. The conduction mechanisms are mainly based on polaron hopping conduction |
| Description: | J. Phys. D: Appl. Phys. 42 (2009) 165005 (8pp) |
| URI: | http://dyuthi.cusat.ac.in/purl/4397 |
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| Mechanism of ac ... se zinc mixed ferrites.pdf | (2.619Mb) |
| Abstract: | Polyfurfural thin films lying in the thickness range of 1300–2000 A˚ were prepared by ac plasma polymerization technique. The current–voltage characteristics in symmetric and asymmetric electrode configuration were studied with a view to determining the dominant conduction mechanism.It was found that the Schottky conduction mechanism is dominant in plasma polymerized furfural thin films.The predominance of Schottky mechanism was further confirmed based on the thermally stimulated current measurements. |
| URI: | http://dyuthi.cusat.ac.in/purl/2832 |
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| Dyuthi-P00388.pdf | (231.2Kb) |
| Abstract: | Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were fabricated by the thermal evaporation technique. Transmission electron micrographs and electron diffraction pattern showed the amorphous nature of the films. Composition of the films was analyzed employing X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy techniques. The film was integrated to a long period fibre grating. It was observed that the resonance wavelength of the fibre grating decreased with an increase in the magnetic field. Change in the resonance wavelength was minimal at higher magnetic fields. Field dependent magnetostriction values revealed the potential application of these films in magnetostrictive sensor devices. |
| URI: | http://dyuthi.cusat.ac.in/purl/2840 |
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| Dyuthi-P00393.pdf | (556.3Kb) |
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