Irreversible Colossal Magnetoresistance in La0.58Dy0.09Ca0.33MnO3

The representative sample La0.58Dy0.09Ca0.33MnO3 of Dy doped La0.67Ca0.33MnO3 rare-earth manganites was investigated.The most important effect of Dy doping is to introducethe magnetoimpurity and form the spin clusters which induce dramatically large CMR in Lao.58Dyo.09Cao.33MnO3. The fitting results of field-induced resistivity decrease to the Brillouin function indicate that the CMR is caused by the spin dependent hopping between spin clusters. It is the magnetic field that reduces the size of spin clusters and induces a field-induced irreversible CMR behaviour.     

Spin coater based on brushless dc motor of hard disk drivers

We have developed a novel programmable, low cost, spin coater to be used for applications where flat substrates are coated with an uniform thin layer of a desirable material. The equipment is built with dc brushless motor present in most of the hard disk drivers (HDDs). The system offers manual control, wide speed range (from 0 to 10,000 rpm), spin speed stability and compact size. The paper also describes the use of such equipment for the fabrication of thin poly(o-methoxyaniline) (POMA) films, which are of particular interest for design organic electronic devices, such as diodes, transistor, sensors and displays.     

Synthetic approach to alloy thermodynamics and kinetics by cluster variation method and path probability method

The cluster variation method of equilibrium thermodynamics is employed to calculate the Ll₀-disorder phase diagram. The stability analysis based on the second-order derivative of the free energy functional with respect to the deviation of correlation functions from their equilibrium values yields the 100 instability locus in the phase diagram. The time evolution of cluster probabilities at the phase transition is investigated on the basis of the path probability method of non-equilibrium statistical mechanics. Thereby the synthetic study of thermodynamics and kinetics based on the cluster variation method and the path probability method is attempted. It is shown that the fluctuation is necessary to drive the ordering reaction above the instability temperature, whereas the spinodal-like ordering transition takes place below the instability temperature. The extension of the present study of a spin system to an alloy system is briefly discussed and a critical problem to be settled is pointed out.     

知母宁清除活性氧作用的研究

用ＥＳＲ及自旋捕捉技术研究了知母宁在均相和非均相体系中对．ＯＨ，Ｏ＾．－２和＾１Ｏ２等几种活性氧的清除，猝灭效果。发现知母宁对．ＯＨ，＾１Ｏ２均有较强的清除和猝灭作用，效果好于维生素Ｅ，并通过动力学方法求得其在均相体系中对＾１Ｏ２的猝灭速率常数为７．２×１０＾８ｍｏｌ＾ｌＬｓ＾－１。     

New effects in highT c superconductors

We show that a proper interpretation of the critical field measurements can distinguish spin fluctuation mechanism from others in the context of the pairing hypothesis. We can predict the existence of a new mode in the mixed state of a superconductor.     

Direct ESR and spin trapping methods for the detection and identification of radical fragments in Nafion membranes and model compounds exposed to oxygen radicals

Direct electron spin resonance (ESR) and spin trapping methods are used in our laboratory in order to identify radical fragments in fluorinated membranes (Nafion) used in fuel cells and in model compounds when exposed to reactive oxygen species. Oxygen radicals were generated by the Fenton reaction, by the photo-Fenton method, and by UV-irradiation of aqueous H₂O₂ solutions. Direct ESR detection led to the identification of fluorinated radical fragments in UV-irradiated Nafion neutralized by Cu(II), Fe(II), and Fe(III) cations and exposed to H₂O₂. In Nafion exposed to the Fenton reagent in the presence of DMPO (5,5-dimethyl-1-pyrroline) as the spin trap, radical adducts of hydroxyl and carbon-centered radicals (CCRs) were detected. A fluorinated model compound, perfluro-(2-ethoxyethane) sulfonic acid (CF₃CF₂OCF₂CF₂SO₃H, PFEESA), that mimics the side chain of Nafion was chosen for study, with the goal to shed light on the more complicated degradation processes in the polymeric membranes. Analysis of the spin adducts obtained from UV-irradiated PFEESA in the presence of H₂O₂ and MNP (2-methyl-2-nitrosopropane) as the spin trap suggested that the side chain of Nafion is a possible site of attack by oxygen radicals.     

Spin assignment of the first discovered superdeformed band ^152Dy（1）

Using the several criteria for the spin assignment of a rotational band based on very general argument,the spin of the lowest level observed in the yrast SD band 152Dy(1) is assigned to be I0=26(Eγ(I0 2→I0)=602.4keV),and it is demonstrated that spin assignments of I0≤25 as well as I-≥27 are in contradiction with these criteria.     

Spin- and charge density oscillations around Ir impurity in α-Fe studied by Fe Mössbauer spectroscopy

Random solution of iridium in ferromagnetic α-Fe of the BCC structure has been investigated by means of the 14.4 keV Mössbauer transition in ⁵⁷Fe at room temperature. Iridium has been randomly substituted on the iron sites with the concentration up to 11 at.%. Contributions to the hyperfine field and isomer shift on the iron nuclei have been determined as the function of the distance between iron nucleus and iridium impurity up to the third co-ordination shell. Iridium atom as the nearest iron neighbor changes iron hyperfine field by +0.66 T, as the second neighbor makes change by −1.88 T and finally as the third neighbor changes the field by +0.70 T. Corresponding changes in the isomer shift are as follows: −0.031, +0.003 and +0.033 mm/s. Hence, it was found that iridium atoms lead to the very strong oscillations in the spin- and charge density around themselves in the α-Fe BCC structure.