Shalendra Kumar

Publications (142) View all

• Article: Influence of Ni2+ substitution on the structural, dielectric and magnetic properties of Cu-Cd ferrite nanoparticles

  Alimuddin, Mohd. Hashim, Sagar E. Shirsath, R.K. Kotnala, Sher Singh Meena, Shalendra Kumar, Aashis Roy, R. B. Jotania, Pramod Bhatt, Ravi Kumar
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  ABSTRACT: Nanoparticles with compositions of Cu0.4−0.5xCd0.2Ni0.4+xFe2−0.5xO4 (0.0 ⩽ x ⩽ 0.5) were successfully synthesized by a citrate–nitrate sol–gel auto combustion route. The combusted powder was calcinated at four hours in a furnace and then slowly cooled to room temperature. The analysis methods of FTIR, XRD, FESEM, VSM and dielectric measurements were used to characterize prepared magnetic particles. The effect of Ni2+ substitution on structural, magnetic and dielectric properties of Cu–Cd ferrite nanoparticles was studied. The comprehensive studies on compositional and frequency dependent dielectric properties were carried out by means of AC conductivity (σac), imaginary dielectric constant (ε′′), loss tangent (tan δ), impedance and dielectric modulus (real and imaginary) measurements in frequency range of 50 Hz–5 MHz at room temperature. The structural properties investigated by using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. X-ray diffraction pattern and FTIR results revealed that synthesized samples are in single phase. It is observed that the dielectric constant (ε′′) and dielectric loss (tan δ) value decreases with increase in Ni2+ concentration (x). At low frequency the Maxwell type interfacial polarization was observed. Magnetization measurement shows that the Curie temperature of the samples increases with Ni2+ concentration, which is explained by a change in the A–O–B super exchange interaction.
  Journal of Alloys and Compounds 10/2013; 573:198–204. · 2.29 Impact Factor
• Source

  Available from: Sher Singh Meena

  Article: Investigation of structural, dielectric, magnetic and antibacterial activity of Cu-Cd-Ni-FeO4 nanoparticles

  Mohd. Hashim, Alimuddin, Sagar E. Shirsath, S. S. Meena, R.K. Kotnala, Ameena Parveen, Aashis S. Roy, Shalendra Kumar, Pramod Bhatt, Ravi Kumar
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  ABSTRACT: Nanoparticles of Cu–Cd–Ni–FeO4 were synthesized by the auto-combustion process using a modified citric acid method. Antibacterial activity, structural, dielectric and magnetic properties were investigated. An assay showed the broad spectrum antibacterial activity of Cu–Cd–Ni–FeO4 against Gram positive and Gram negative pathogenic bacterial strains. The existence of single phase cubic spinel structure of ferrites was confirmed by X-ray diffraction measurement. Fourier transform infrared spectroscopy shows the two main absorption bands at lower frequency region. Surface morphology and compositional features were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy analysis, respectively. Results indicated that the nanosize particles greatly influenced the antibacterial activity, as well as structural, dielectric and magnetic properties of the samples. Magnetic measurements of the samples were carried out by means of vibrating sample magnetometry and Mössbauer spectroscopy. Magnetic properties are strongly affected by Ni2+ substitution.
  Journal of Magnetism and Magnetic Materials 09/2013; 341(September 2013):148–157. · 1.78 Impact Factor
• Source

  Available from: Sagar E. Shirsath

  Article: Synthesis and characterizations of Ni2+ substituted cobalt ferrite nanoparticles

  Mohd. Hashim, Alimuddin, Shalendra Kumar, Sagar E. Shirsath, R.K. Kotnala, Jyoti Shah, Ravi Kumar
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  ABSTRACT: Nanocrystalline Co–Ni ferrites bearing chemical formula Co0.5Fe2−xNi0.5+1.0xO4 for x ranging from 0.0 to 0.4 with the step increment of 0.1 were successfully synthesized by sol gel auto-combustion method. The energy dispersive X-ray analysis (EDAX) results give relevant information for the homogenous mixing of the Co, Fe, and Ni atoms as expected from the synthesis. The phase identification of the materials by XRD reveals single phase with cubic symmetry. The presence of functional group was identified by Fourier transform infrared spectroscopic studies. The dielectric parameters such as dielectric constant ((ε′), dielectric loss (ε″) & dielectric loss tangent (tan δ) have been studied at room temperature in the frequency range 42 Hz−5MHz and is explained in the light of interfacial polarization, arising from the heterogeneous nature of ferrite structure. The decrease in DC resistivity with increasing Ni concentration is attributed to the Verwey mechanism between Fe2+ ↔ Fe3+, Co2+ ↔ Co3+ and Ni2+ ↔ Ni3+. Ni-doped nanocrystalline cobalt ferrite samples exhibit a very large value for dielectric constant of the order of 1013. Complex impedance analysis has been used to separate grain and grain boundary in the studied samples. It is observed that saturation magnetization (Ms) decreases with increase in nickel contents which is attributed to the substitution of magnetic Fe3+ ions of 5 μB by less magnetic Ni2+ ions of 2 μB. The analysis of the Mössbauer spectra shows the hyperfine field, relative % area and isomer shift decreases whereas quadruple splitting and line width increases at A- and B-sites on increasing the substitution of Ni2+ ions.
  Materials Chemistry and Physics 05/2013; 139(2-3):364–374. · 2.23 Impact Factor
• Source

  Available from: Sher Singh Meena

  Article: Influence of Ni2+ substitution on the structural, dielectric and magnetic properties of Cu–Cd ferrite nanoparticles

  Mohd. Hashim, Alimuddin, Sagar E. Shirsath, R.K. Kotnala, Sher Singh Meena, Shalendra Kumar, Aashis Roy, R.B. Jotania, Pramod Bhatt, Ravi Kumar
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  ABSTRACT: Nanoparticles with compositions of Cu0.4�0.5x Cd0.2Ni0.4+x Fe2�0.5x O4 (0.0 6 x 6 0.5) were successfully synthesized by a citrate–nitrate sol–gel auto combustion route. The combusted powder was calcinated at four hours in a furnace and then slowly cooled to room temperature. The analysis methods of FTIR, XRD, FESEM, VSM and dielectric measurements were used to characterize prepared magnetic particles. The effect of Ni2+ substitution on structural, magnetic and dielectric properties of Cu–Cd ferrite nanoparticles was studied. The comprehensive studies on compositional and frequency dependent dielectric properties were carried out by means of AC conductivity (rac), imaginary dielectric constant (e 00), loss tangent (tand), impedance and dielectric modulus (real and imaginary) measurements in frequency range of 50 Hz–5 MHz at room temperature. The structural properties investigated by using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. X-ray diffraction pattern and FTIR results revealed that synthesized samples are in single phase. It is observed that the dielectric constant (e 00) and dielectric loss (tand) value decreases with increase in Ni2+ concentration (x). At low frequency the Maxwell type interfacial polarization was observed. Magnetization measurement shows that the Curie temperature of the samples increases with Ni2+ concentration, which is explained by a change in the A–O–B super exchange interaction.
  Journal of Alloys and Compounds 03/2013; 573:198–204. · 2.29 Impact Factor
• Source

  Available from: Sagar E. Shirsath

  Article: Influence of Cr3+ ion on the structural, ac conductivity and magnetic properties of nanocrystalline Ni-Mg ferrite

  Mohd. Hashim, Alimuddin, Shalendra Kumar, Sagar E. Shirsath, R. K. Kotnala, Jyoti Shah, Ravi Kumar
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  ABSTRACT: Nanocrystalline samples of the Ni–Mg ferrite with the general chemical formula Ni0.5Mg0.5CrxFe2�xO4 (0rxr1.0, in the step of 0.2) have been synthesized by the citrate-gel auto combustion route. The synthesized samples were characterized by means of XRD, EDAX, FT-IR, UV–visible, dielectric, ac impedance spectroscopy, and AFM, SEM, TEM and FC/ZFC measurements. X-ray powder diffraction of all the samples were carried out at room temperature to check the formation of the required products and structural related properties. The elemental analysis as obtained from the EDAX measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. IR studies confirm two main absorption bands in the frequency range of 400–800 cm�1, arising due to the tetrahedral (A) and octahedral [B] stretching vibrations. Impedance spectroscopy techniques have been used to study the effect of grain and grain boundary on the electrical properties of the prepared samples. The samples were zero field cooled (ZFC) to 100 K. Typical blocking temperature effects were observed below the temperature of about 129 K. The obtained results have been discussed so as to bring out the role of chromium substitution on the structural, dielectric and magnetic properties of Ni–Mg ferrites.
  Ceramics International 03/2013; 39(2):1807–1819. · 1.75 Impact Factor