Chiranjib Nayek

Indian Institute of Technology Madras | IIT Madras

Core/shell Fe3O4/�-Fe2O3 nanoparticles have been designed as a promising agent for magnetic hyperthermia and contrast agents for MRI imaging applications, because of their high magnetic moment and biocompatibility. Three sets of core/shell nanoparticles with the same core diameter of 8 nm and shell thicknesses of 1, 3 and 5 nm were synthesized by c...

The phase composition, the structure of cores and shells, and the dependences of the shell thickness on the fabrication technique were determined by Mössbauer spectroscopy for core/shell Fe3O4/γ-Fe2O3 magnetic nanoparticles (MNPs) with Fe3O4 cores of a fixed size (8 nm) and γ-Fe2O3 shells of a varying thickness (1, 3, or 5 nm). A layer on the MNP s...

The phase composition, the structure of cores and shells, and the dependences of the shell thickness on the fabrication technique were determined by Mössbauer spectroscopy for core/shell Fe_3O_4/γ-Fe_2O_3 magnetic nanoparticles (MNPs) with Fe_3O_4 cores of a fixed size (8 nm) and γ-Fe_2O_3 shells of a varying thickness (1, 3, or 5 nm). A layer on t...

(La0.7Sr0.3MnO3)1−x–(BaTiO3)x solid solution samples (x = 0, 0.03, and 0.08) were synthesized by sol–gel route. Pure La0.7Sr0.3MnO3 has orthorhombic structure with Pbnm space group whereas solid solution samples possess rhombohedral structure with R-3c space group. Temperature-dependent ac susceptibility at different frequencies and memory effect c...

Understanding the size dependent magnetic anisotropy of iron oxide nanoparticles is essential for the successful application of these nanoparticles in several technological and medical fields. PEG-coated iron oxide (Fe3O4) nanoparticles with core diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The morphol...

Understanding saturation magnetization and its behavior with particle size and temperature are essential for medical applications such magnetic hyperthermia.We report the effect of shell thickness and field cooling on the saturation magnetization and its behavior with temperature in Fe3O4/γ-Fe2O3 core/shell nanoparticles of fixed core diameter (8 n...

We have carried out extensive measurements on novel Fe₃O₄-γ-Fe₂O₃ core-shell nanoparticles of nearly similar core diameter (8 nm) and of various shell thicknesses of 1 nm (sample S1), 3 nm (sample S2), and 5 nm (sample S3). The structure and morphology of the samples were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM)...

Polyethylene glycol (PEG) coated magnetic Fe 3O 4 nanoparticles with diameters of 12 nm, 15 nm, and 16 nm were synthesized by the usual co-precipitation method. The structure and morphology of the samples were characterized using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The ac magnetic susceptibility mea...

We report the transition from robust ferromagnetism to a spin-glass state in nanoparticulate La0.7Sr0.3MnO3 through solid solution with BaTiO3. The field- and temperature-dependent magnetization and the frequency-dependent ac magnetic susceptibility measurements strongly indicate the existence of a spin-glass state in the system, which is further c...

In this work, the enhancement in magnetic moment in Lu doped BiFeO 3 is reported. Sol–gel synthesized Bi 1−x Lu x FeO 3 (x = 0, 0.02, 0.04 and 0.05) were characterized for their phase, magnetic properties, thermal analysis and Raman scattering studies. The X-ray diffraction study revealed the segregation of rare earth garnet as secondary phase. The...

We have synthesized the phase-pure (1 − x)BaTiO3-xLa0.7Sr0.3MnO3 (x = 0.1 and 0.3) magnetoelectric composites without interdiffusion among the existing phases. The magnetic measurements revealed an anomaly at the ferroelectric Curie temperature (393 K) of BaTiO3, and the dielectric data revealed an anomaly at the ferromagnetic transition temperatur...

Low doped colossal magnetoresistance La1-xBaxMnO3+δ nanoparticles are synthesized by sol-gel method along with the parent compound LaMnO3+δ. The Reitveld refinements on the XRD patterns show that they are crystallized in structure other than their stoichiometric bulk. The crystal structure indicates excess oxygen/cationic vacancies in the compound....

The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol-gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Ar...

We report structural and magnetic properties of rare earth doped Bi 0.95 R 0.05 FeO 3 (R ¼ Y, Ho, and Er) submicron particles. Rare earth doping enhances the magnetization and the magnetization shows an increasing trend with decreasing dopant ionic radii. In contrast to the x-ray diffraction pattern, we have seen a strong evidence for the presence...

We have investigated the structure, magnetic and dielectric properties of PVDF- La0.7Sr0.3MnO3polymer nanocomposite thick film fabricated by dip coating tech- nique along with the magnetodielectric effect. The structure and dielectric properties show the enhanced β phase in the composite compared to the PVDF film. The cou- pling between the ferroel...

We report the magnetoelectric properties of La0.7Sr0.3MnO3–BaTiO3 core–shell nanostructure synthesized by sol–gel method. X-ray diffraction analysis suggests that the BaTiO3 undergoes large strain in the core–shell structure which can be attributed to lattice induced strain. Interestingly, the core–shell nanoparticle exhibits enhanced magnetization...

Single phase Bi(1-x)EuxFeO3 multiferroic nanoparticles were synthesized by tartaric acid assisted sol-gel method and the effect of Eu substitution in Bismuth ferrite (BFO) was investigated on the structural, optical and magnetic properties. It was observed a gradual structural transition from rhombohedral R3c to orthorhombic Pbnm with the increase...

Nanocrystalline colossal magnetoresistance (CMR) La1-xRxMnO3 (R = Ba, Ca ; x= 0, 0.05, 0.1 and 0.2) compounds were synthesized by sol-gel method using lanthanum acetate, manganese acetate and carbonates of alkaline earth cations as precursors. X ray diffraction (XRD) patterns confirm the compound formation without any impurity phases. The structura...