Preeti Thakur

Magnetic behaviour of Ni0.4Zn0.6Co0.1Fe1.9O4 spinel nano-ferrite

Nanoparticles of the spinel ferrite Ni0.4Zn0.6Co0.1Fe1.9O4, have been synthesized by a co-precipitation method. The x-ray diffraction patterns of the particles confirmed the formation of single-phase cubic spinel structure. The Langevin function fitting on M-H data at 300 K gives a log-normal particle size distribution with median diameter of 59.6 nm and standard deviation of 0.6. The isothermal dc magnetization studies have been performed using the superconducting quantum interface device and vibrating sample magnetometer in the temperature range of 5-300 K. These measurements show that the sample is superparamagnetic above the blocking temperature TB ∼ 253 K when an external magnetic field of 20 Oe is applied. The reduction in saturation magnetization in case of nanoparticles may be attributed to the fact that magnetic moments in the surface layers outside the core are in the state of frozen disorder. A doublet observed in the Mossbauer study also confirms the superparamagnetic behavior and nanocrystall...

Enhancement in Dielectric and Magnetic Properties of

Indium substituted nano nickel zinc ferrites Ni_0.5Zn_0.5In_xFe_2-xO₄ with <i>x</i>=0, 0.1, 0.2 and 0.3 are synthesized by a coprecipitation method. Magnetic and dielectric properties are studied over a frequency range 1-30 MHz. Initial permeability is found to be in the range of 9-19 with a magnetic loss tangent of 10^-1-10^-2 . The dielectric constant is noticed in the range of 11-17 along with low dielectric loss tangent (10^-1-10^-3). The composition with x=0.2 is found to have the highest specific saturation magnetization of 78.8 emu/g. Appreciable dielectric and magnetic values along with low losses can be correlated to small grain size and better compositional stoichiometry obtained as a result of processing by coprecipitation method. These fascinating dielectric and magnetic properties of these materials reveal a direction for high-frequency applications.

{\rm In}^{3+}

A nanoferrite series of composition Ni0.5−xMnxMg0.5Fe2O4 with x = 0, 0.1, 0.2, 0.3 and 0.4 has been prepared by a hydrothermal method. X-ray diffraction (XRD) confirmed the formation of cubic spinel structure. The average crystallite size is found to be in the range of 28–48 nm. The lattice parameter is found to increase linearly with an increase in Mn2+ content. Field Emission Scanning Electron Microscopy micrographs indicate that the samples have almost uniform sized crystallites with uniform grain growth. Fourier Transform Infrared (FTIR) Spectroscopy studies showed two absorption bands close to 603 and 400cm−1 for the tetrahedral and octahedral sites respectively. Saturation magnetization attained a maximum value of 34.15 emu/g at x = 0.3 and then decreases for higher concentrations of Mn2+ ions. Activation energy for compositions Ni0.3Mn0.2Mg0.5Fe2O4 and Ni0.2Mn0.3Mg0.5Fe2O4 are found to be 0.371 eV and 0.471 eV, respectively. For composition Ni0.2Mn0.3Mg0.5Fe2O4, maximum value of observed density, minimum porosity, maximum value of saturation magnetization, maximum initial permeability and minimum value of coercivity is obtained. DC resistivity is found to be of the order of 108Ωcm. The obtained results have been explained based on possible mechanisms, models and theories.

Substituted Ni-Zn Nano-Ferrites by Coprecipitation Method

Abstract Recent advances in engineering lead to the fabrication of nanomaterials with unique properties targeted toward specific applications. The use of nanotechnology in agriculture, in particular for plant protection and production, is an under‐explored area in the research community. Fungal diseases are one of the leading causes of crop destruction and, in this context, the antifungal effect of nanoparticles of cobalt and nickel ferrite against phytopathogenic fungi is reported here. As a proof of concept, it is also shown how such nanoparticles can be used as fungicides in plants. The developed cobalt and nickel ferrite nanoparticles (CoFe2O4 and NiFe2O4) are successfully tested for antimycotic activity against three plant‐pathogenic fungi: Fusarium oxysporum, Colletotrichum gloeosporioides, and Dematophora necatrix. In addition, it is also observed that these ferrite nanoparticles reduce the incidence of Fusarium wilt in capsicum. The study suggests that nanoparticles of CoFe2O4 and NiFe2O4 can be used as an effective fungicide in plant disease management.

Effect of high spin Mn2+ /Mn3+ ions on microstructural, optical, magnetic and electrical properties of hydrothermally prepared Ni–Mg nanoferrites

Abstract Nanostructured ferroxide particles with nominal composition Mn0.4Zn0.6In0.2Fe1.8O4 are prepared by a citrate precursor method. The prepared powder is pre-sintered at 600 ℃ and finally sintered at 900 ℃ for three hours each. X-ray diffraction, transmission electron microscopy and scanning electron microscopy confirmed the size, structure and morphology of the nanoferrite. Single phase spinel structure is confirmed from XRD study with particle size 25 nm and 45 nm before and after sintering. The superparamagnetic behaviour is confirmed by vibrating sample magnetometer study with no hysteresis. The resonance in electromagnetic properties is observed beyond 300 MHz, making this material suitable for high to very high frequency (10–300 MHz) applications.

Nanomaterial fungicides: In vitro and in vivo antimycotic activity of cobalt and nickel nanoferrites on phytopathogenic fungi

Hexaplana W-type barium ferrite of nominal composition BaZn1.5Co0.5Fe16O27 was prepared by a co-precipitation method. The structural and electrical properties were studied at different sintering temperatures. The average crystallite size was found to be in the range 46 ‒ 57 nm calculated by Scherrer formula, which means crystallite size increases with an increase in sintering temperature. Fourier transform spectroscopy reveals the ferrite peaks in the range 577.19 cm−1 ‒ 595.48 cm−1 confirming the hexagonal structure of ferrites. Metal-Semiconductor transition temperature was found to be decrease as the sintering temperature increases, whereas the trend for activation energy was found to be increasing.

Structural, Magnetic and Electromagnetic Characterization of In3+ Substituted Mn-Zn Nanoferrites

The effective relative permittivity and effective relative permeability of magneto-dielectric materials when used as substrate for microstrip antenna shows interdependency. This dependency was analyzed through simulation and verified by synthesizing nano composite ferrite. The 40nm nano crystallite size particles were synthesized using a co- precipitation method. Matching values of complex permittivity (e* = 4.2-0.1j) and complex permeability (μ* = 4.3-0.2j) at 1 GHz were obtained from the electromagnetic characterization. The microstrip antenna with coaxial feed was fabricated and the interdependence of relative permittivity and relative permeability was verified. An error of 7% in the drawn length was observed for er and μr of the order of 4. The magneto-dielectric material with composition Mn0.5Zn0.3Co0.2Fe2O4+BaFe12O19 proposed in this paper definitely can be proposed as a substrate material for miniaturized antenna. The antenna with desired resonant frequency can be fabricated by calculating the effe...

Study of electrical properties of W-type barium hexaferrite for high frequency application

Ni-Zn substituted M-type barium ferrite nanocomposite has been prepared via citrate precursor method. Nanocomposite having composition BaNi0.5Zn0.5Fe11O19 was sintered at 900°C for 3hrs and characterized by using different characterization techniques. X-ray diffraction (XRD) confirmed the formation of double phase with most prominent peak at (114). Average crystallite size for pure BaM and BNZFO were found to be 36 nm & 45 nm. Field emission scanning electron microscopy (FESEM) confirmed the formation of hexagonal platelets with a layered structure. Magnetic properties of these samples were investigated by using vibrating sample magnetometer (VSM). Magnetic parameters like saturation magnetization (Ms), coericivity (Hc) and squareness ratio (SQR) of nanocomposite were found to be 60 emu/g, 3663 Oe and 0.6163 respectively. These values were noticed to be higher as compared to pure BaM. Enhanced magnetic properties of nanocomposite were strongly dependent on exchange coupling. Therefore these properties mak...