Temperature-dependent Mössbauer and dielectric studies of Mg0.95Mn0.05Fe1.0Ti1.0O4

The effect of tetravalent Ti⁺⁴ substitution in Mg_0.95Mn_0.05Fe₂O₄ on its magnetic and electrical properties has been studied using X-ray diffraction, Mössbauer spectroscopy, isothermal dc magnetization and dielectric measurements. X-ray diffraction studies have shown the structural transformation from cubic to tetragonal with the Ti⁺⁴ substitution. The Mössbauer spectra of Mg_0.95Mn_0.05Fe_1.0Ti_1.0O₄ recorded in the temperature range 20-300 K shows the presence of the magnetic as well as quadrupole interactions. The isothermal hysteresis loop infers that the system exhibits a ferrimagnetic ordering at room temperature. The Zero-field-cooled (ZFC) and field-cooled (FC) magnetization studies support ferrimagnetic ordering of Mg_0.95Mn_0.05Fe_1.0Ti_1.0O₄ at room temperature. Signatures of ferroelectric transition have been observed in the temperature range 200-300 K from dielectric measurements. The observed magnetic and dielectric behaviour indicate that this material exhibits multiferroic behaviour.     

Column chromatographic separation of metal ions on 1-(2-pyridylazo)-2-napthol modified amberlite IR-120 resin

Cation exchange resin, Amberlite IR-120, has been modified by the sorption of 1-(2-pyridylazo)-2-napthol (PAN) at pH 6.0. The optimum conditions for the sorption of PAN on the resin have been established. The maximum sorption of PAN was found to be 8.70 micromol/g. In order to explore the separation possibilities of the material, distribution coefficients of a number of metal ions were determined in various solvent systems. A number of binary separations of metal ions of analytical interest have been carried out using columns packed with this material. In order to demonstrate the practical utility of this material, Zn2+ and Hg2+ have been selectively separated from synthetic mixtures of metal ions and assay of Zn2+ and Fe2+ in commercially available pharmaceutical tablets; namely Fesofor-Z and FE-Z, was carried out.     

On the polarization measurements of the Mössbauer gamma-rays

Summary A theoretical analysis of polarization of the M?ssbauer radiation has been attempted by using the Stokes parametrization technique. Explicit results for theM1 (3/2⁻→1/2⁻) andE2 (2⁺→0⁺) radiations in relation to polarization and hyperfine-field parameters in the crystal fixed-axis system are discussed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Mössbauer study of some biological iron complexes

Some biological complexes containing iron are investigated experimentally at room temperature using the Mössbauer resonance. The complexes show quadrupole doublet and Kramer’s degeneracy is found to exist. The electric field gradient, difference ins-electron densities and quadrupole coupling constant have been calculated in each case. These parameters are used to obtain information on the surroundings of the Mössbauer atom     

Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn_(1−x)Zn_xFe₂O₄ were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.     

Study of dielectric and ac impedance properties of Ti doped Mn ferrites

We have reported dielectric and ac impedance properties of Ti doped Mn_1+xFe_2−2xO₄ (0x0.5) ferrites prepared by solid-state reaction method, using dielectric and impedance spectroscopy in the frequency range of 42 Hz–5 MHz, between the temperatures (300K–473K). The dielectric constant and dielectric loss (tan δ) decreases with increasing frequency but these parameters increase with increasing temperature. The dielectric loss tangent curves exhibit dielectric relaxation peaks at high frequencies (3.6 kHz–5 MHz), which are attributed to the coincidence of the frequency of charge hopping between the localized charge states and the external field. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell–Wagner’s two-layer model and the hopping of charge between Fe²⁺ and Fe³⁺ as well as between Mn³⁺ and Mn²⁺ ions at B-sites. The complex impedance analysis has been used to separate grain and grain boundary in studied samples. Two semicircles corresponding to grain and grain boundary have been observed at low temperature, while only one semicircle has been seen at high temperatures. The resistance of grain and grain boundary both increase with Ti⁴⁺ doping.     

Electronic structure studies of Mg0.95Mn0.05Fe2−2xTi2xO4 (0x0.8)

The electronic structure of Mg_0.95Mn_0.05Fe_2−2xTi_2xO₄ (0x0.8) compound is investigated using near edge X-ray absorption fine structure, (NEXAFS) spectroscopy measurements, carried out at O K, Fe and Ti L_3,2-edges at room temperature. The O K-edge spectra indicate that the Fe 3d orbitals have been considerably modified and a new spectral feature start dominating in the pre-edge region at higher Ti doping. The Fe 2p NEXAFS spectra exhibit a mixed valent Fe²⁺/Fe³⁺ states apart from the conversion of Fe³⁺ to Fe²⁺ with the substitution of Ti ions. The Ti L_3,2-edge spectra indicate that Ti ions remain unchanged at 4+ state. These variations in the host electronic structure due to Ti substitution are consistent with the dielectric and transport properties of the material.