Nanocrystalline NiZn ferrite, Ni0.5Zn0.5Fe2O4, having particle size in the range 6-10 mn, has been synthesized by an auto-combustion method. The nanosized ferrite powder formed at a low temperature is annealed at different temperatures in the range 473-1273 K and characterized by X-ray diffraction, vibrating sample magnetometry, Mossbauer spectroscopy, transmission electron microscopy and scanning electron microscopy. Magnetic transition temperature broadening up to 773 K is observed for the nanosized sample, compared to the T-c = 563 K for the bulk material. Critical particle diameter (D-c) is found to be similar to 40 nm at which maximum coercivity is obtained for the powder sample annealed at 973 K. Similarly, high room temperature magnetization, comparable to that of the bulk material, is obtained for the powders annealed at 1073 K, with a maximum particle size of similar to 50 nm. Very little grain growth is observed for the powders annealed above 1073 K. The results show that, optimum magnetic properties can be achieved for fine particle NiZn ferrite powders synthesized by a low-temperature auto-combustion method and processed at relatively lower temperatures.

Magnetic exchange and charge transfer mechanism in dimeric (1) [Cu(Lw)(2)H2O](2) and monomeric (2). [Cu(phth)(2)] complexes of lawsone (2-hydroxy-1, 4-naphthoquinone) and phthiocol (3-methyl-2-hydroxy 1,4-naphthoquinone) are described. Magnetic susceptibility measurements of (1) are fitted to Heisenberg's isotropic spin pair (S'=1.1) model and tetranuclear (S'= 1/2, 1/2, 1/2, 1/2) spins in a two dimensional model. Both models result in intradimer antiferromagnetic coupling (J=-44.4 cm(-1)) between [Cu(NSQ)](2) units and ferromagnetic coupling (zJ(1)=28.5 cm(-1)) between one Cu(II)NSQ coordinated unit (where NSQ=naphtho-semiquinone).Latter interaction leads to a triplet ground state and triplet-triplet intradimer interaction governs the "quintet state" at room temperature, as detected from X- and Q-band EPR studies. The zero-field split interaction (0.024 cm(-1)) exhibits contributions from D-pd (-0.071 cm(-1)) and combined D-d and D-anti (+0.095 cm(-1)) interactions. The intradimer exchange is due to a stacked (S'=1.1) spin pair with r=3.04 Angstrom. The monomeric complex (2) is devoid of such interactions due to the bulky methyl group at C3 position of quinonoid ring.Cyclic voltammograms of (1) and (2) show an anodic peak at +0.22 V, assigned to Cu(0)-->Cu(II) charge transfer. Only one redox couple at E-1/2 = -0.687 V due to NSQdouble left right arrowCAT (catechol) charge transfer leads to radical coordination in (1). However quasireversible NQdouble left right arrowNSQ redox couple at E-1/2 = -0.525 V together with an irreversible NSQ-->CAT reduction peak in (2) at E-1/2 = -0.75 V indicate fully the presence of oxidized (NQ) i.e. naphthoquinone ligation in (2).

A new combustion route for the synthesis of γ-Fe 2 O 3 is reported by employing purified a-Fe 2 O 3 as a precursor in the present investigation. This synthesis which is similar to a self propagation combustion reaction, involves fewer steps, a shorter overall processing time, is a low energy reaction without the need of any explosives, and also the reaction is completed in a single step yielding magnetic iron oxide i.e. γ-Fe 2 O 3 .The as synthesized γ-Fe 2 O 3 is characterized employing thermal, XRD, SEM, magnetic hysteresis, and density measurements. The effect of ball-milling on magnetic properties is also presented.

Organically capped zinc sulfide nanoparticles doped with different manganese concentrations were prepared under similar conditions. Only the doping concentration was varied. Photoluminescence and electron-spin-resonance (ESR) investigations show some new results. At an optimum concentration of Mn doping a maximum in the photoluminescence is reached, whereas photoluminescence quenching occurs at higher concentrations. ESR investigations show that the spectra arise due to four different contributions of Mn ions, viz., (1) Mn(S-I) in tetrahedral cationic substitution site with T-d symmetry, (2) isolated Mn ions at the surface or interstitial locations (S-II) with octahedral symmetry (O-h) (3) Mn-Mn dipolar interactions (S-III), and (4) exchange-coupled Mn clusters (S-IV) in various proportions. Linewidths for all these (S-I-S-IV) differ from each other. Identification of these components suggests that S-I may be responsible for the photoluminescence increase, whereas S-II-S-IV may be responsible for the luminescence quenching in nanoparticles.

Nanoparticles of zinc sulphide have been synthesized by a chemical method. Mercaptoethanol is used to passivate the surface of the particles. Under certain conditions highly luminescent particles emitting blue light at ∼425 nm can be synthesized. This blue light emission in nanoparticles of zinc sulphide is observed to be completely quenched when doped with iron or nickel metal ions.

The composition with x=0.15 in the spin glass regime (0⩽x⩽0.18) of the perovskite system, La1−xSrxCoO3, is investigated in detail to understand the unusual magnetic properties reported in the literature. AC susceptibility and field-cooled and zero-field-cooled magnetization measurements give sufficient evidence for compositional inhomogeneity as the origin of the magnetic anomalies. A well-defined spin glass behavior is obtained only for a highly homogeneous sample.

In this paper, we report the study of the magnetic properties of (Li 0.5-x/2 Mu 0.1 Zu x Fe 2.35-x/2 O 4 ) films with x=0, 0.16, 0.32, 0.48. The films were deposited on fused quartz substrates by rf sputtering technique under various deposition conditions. The magnetic properties of the films annealed at 750°C are being reported. The M a values of the films deposited at a rf power of 240 W in argon atmosphere were found to be smaller than the corresponding bulk values. The M a value was found to be maximum at x=0.32, similar to the bulk. The H c values of the films are much higher than the bulk values and decrease as a function of x.

Semisynthetic Human Insulin (SHI) has been available in India for approximately two years and is well accepted. Biosynthetic Human Insulin (BHI) ( genetically engineered hu man insulin o f Sacchromyces Cervisase origin) is likely to be shortly introduced. An open multicentric clinical trial t o compare the e fficacy and safety o f BHI with SHI was conducted over a twenty week period in ninety insulin requiring diabetics receiving mixture of short acting and intermediate acting insulin twice. There was neither a statistically significant change in insulin d ose nor a c hange in the parameters of control, during the period of study, indicating that the two human insulin's been practically indistinguishable clinically. Both insulins were well t olerated with no significant adverse e vent recorded. The results of the trial provide adequate evidence to conclude that BHI is as effective a nd safe as SHI and change over can be made dose to dose, without any problems.

The ternary systems Fe0.968−xMnxSi0.032 with 0 ≦ x ≦ 0.082 are studied for their mechanical, magnetic, and Mössbauer properties at room temperature. The trend shown by the hardness, the relative Mössbauer peak areas, and the intensities of the Mossbauer spectra for different Fe sites are indicative of short-range order and it is found that the intensities are best explained when impurity-impurity separation is restricted to a √3. The observed variations in the central shift and magnetic hyperfine field are attributed to the 4s band contribution of Mn atoms. Die ternären Fe0,968-xMNxSi0,032-Systeme mit 0 ≦ x ≦ 0,082 werden hinsichtlich ihrer mechanischen, magnetischen und Mößbauer-Eigenschaften bei Zimmertemperatur untersucht. Der durch Hürte, der relativen Flächen der Mößbauermaxima und den Intensitäten der Mößbauerspektren für verschiedene Fe-Plätze nachgewiesene Trend weist auf Nahordnung hin und es wire gefunden, daß die intensitäten am besten erklärt werden können. wenn der Störstellen-Störstellen Abstand auf a √3 begrenzt ist. Die beobachteten Änderungen der zentralen Verschiebung und des magnetischen Hyperfeinfeldes werden den Beiträgen der Mn-Atome zum 4s-Band Zugeordnet.

Nuclear electric field gradient (EFG) parameters for Fe2+ ions in ferroelectric lithium niobate are determined using both single crystal orientation experiments and magnetic perturbation technique for polycrystalline samples. The results show clearly the presence of an axially symmetric EFG with no drastic change in the surrounding local environment. The different microscopic models, proposed to explain photorefractive processes in iron doped lithium niobate, are compared and critically reviewed with our experimental results.

Single crystals and ceramics of BaTiO3 and SrTiO3 have been studied by Mossbauer spectroscopy. The materials were investigated as sources and absorbers, doped with Fe57 (Co57) and Sn119. In the preparation of the samples various parameters (temperature, atmosphere, impurity concentration etc.) have been changed. It turned out to be a difficult problem to incorporate Fe into BaTiO3 or SrTiO3 lattices at the Ti4+ site. Thermal doping of single crystals was unsuccessful, in this case a second phase was formed by the addition of Fe57 and Co57. In melt grown BaTiO3 crystals a few hundred ppm Fe could be incorporated in the lattice trivalently. In contrast, Sn is relatively easy to introduce into BaTiO3 and the Mossbauer spectrum of a melt grown single crystal shows a very sharp line. No effects of phase transitions on the hyperfine parameters or the Debye Waller factor could be detected.

The paper reports synthesis and physical characterisation of a new iron(III) porphyrin which shows unusual features of quantum mechanically mixed ground state in its magnetic properties. Magnetic susceptibility (300−3·6 K) and Mössbauer spectroscopy (300−77 K) studies of the compound are described and discussed with reference to some bacterial ferricytochromeC' exhibiting similar spin-mixed ground state.