Dynamic Radio-Frequency Transverse Susceptibility in Magnetic Nanoparticle Systems

A novel resonant method based on a tunnel-diode oscillator (TDO) is used to study the dynamic transverse susceptibility in a Fe nanoparticle system. The magnetic system consists of an aggregate of nanometer-size core (Au)-shell (Fe) structure, synthesized by reverse micelle methods. Static and dynamic magnetization measurements carried out in order to characterize the system reveal a superparamagnetic behavior at high temperature. The field-dependent transverse susceptibility at radio-frequencies (RF), for different temperatures reveals distinct peak structure at characteristics fields (H_k, H_c) which changes with temperature. It is proposed that relaxation processes could explain the influence of the temperature on the field dependence of the transverse susceptibility on the MI.Comment: 3 pages, 2-column, 3 figures, To be published in J. Appl. Phys. 2000 (44th Annual MMM proceedings

Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal

We have investigated the specific heat of optimally-doped iron chalcogenide superconductor Fe(Te0.57Se0.43) with a high-quality single crystal sample. The electronic specific heat Ce of this sample has been successfully separated from the phonon contribution using the specific heat of a non-superconducting sample (Fe0.90Cu0.10)(Te0.57Se0.43) as a reference. The normal state Sommerfeld coefficient gamma_n of the superconducting sample is found to be ~ 26.6 mJ/mol K^2, indicating intermediate electronic correlation. The temperature dependence of Ce in the superconducting state can be best fitted using a double-gap model with 2Delta_s(0)/kBTc = 3.92 and 2Delta_l(0)/kBTc = 5.84. The large gap magnitudes derived from fitting, as well as the large specific heat jump of Delta_Ce(Tc)/gamma_n*Tc ~ 2.11, indicate strong-coupling superconductivity. Furthermore, the magnetic field dependence of specific heat shows strong evidence for multiband superconductivity

Achromatic angle-insensitive infrared quarter-wave retarder based on total internal reflection at the Si–SiO2 interface

An achromatic infrared (λ = 1.2–4 μm), Si-prism quarter-wave retarder (QWR) is described that uses total internal reflection at a buried Si–SiO2 interface at an angle of incidence φ near 33°, where ∂Δ/∂φ = 0. The retardance Δ deviates from 90° by \u3c±2° within a field of view of ±10° (in air) over the entire bandwidth. Because the SiO2 layer at the base of the prism is optically thick, this QWR is unaffected by environmental contamination

Magneto-impedance of glass-coated Fe-Ni-Cu microwires

The magneto-impedance (MI) of glass-coated Fe-Ni-Cu microwires was investigated for longitudinal radio-frequency (RF) currents up to a frequency of 200 MHz using an RF lock-in amplifier method. The MI, defined as DZ/Z = [Z(H)-Z(H=0.3T)]/Z(H=0.3T), displays a peak structure (negative MI) at zero field for RF currents with frequencies less than 20MHz and this crosses over to a sharp dip (positive MI) at higher frequencies. This crossover behavior is ascribed to the skin-depth-limited response primarily governed by the field-dependence of the permeability. Large saturation fields (300 to 600 Oe) and other anomalies indicate the possible influence of giant magneto-resistance (GMR) on the MI.Comment: 3 pages, 2-column, 3 figures. To be published in J. Appl. Phys. 2000 (44th MMM conference proceedings

Efficiency of the national drug pacovirin in the treatment of infectious mononucleosis in children

National Center of Public Health, the Republic of Moldova, Municipal Infectious Diseases Hospital for Children, Chisinau, Toma Ciorba Hospital of Infectious Diseases, Chisinau, the Republic of MoldovaBackground: In the article are presented the clinical results of the treatment of children with infectious mononucleosis where the basic therapy has been combined with the administration of the local drug pacovirin which has antiviral, immunomodulatory, interferonogenic and antioxidant activity. Material and methods: Pacovirin has been administered for one month by 50 mg capsules 2 times a day per os. The object of study has been presented by 175 patients (84 patients in the experimental group and 91 ones in the comparison group) and the records of the patients surveillance (form 003/e), containing the clinical diagnosis of infectious mononucleosis with Epstein-Barr virus and hepatitis syndrome. The duration of the treatment has been one month, the doses being age-appropriate and applied 2 times a day. Results: The administration of pacovirin as a medicinal remedy in addition to the traditional treatment, in accordance with the method proposed by us, has led to the more intensive normalization of clinical and laboratory indices, decrease of the pathological process and the rapid recovery of the patients, as well as the more intensive normalization of biochemical indices and significant reduction of the duration of the main clinical signs in the experimental group compared with the control group. Conclusions: The drug pacovirin has a positive effect on the main clinical signs of general toxic syndrome and digestive disorders, which have disappeared in a significant number of patients after the treatment. In most patients in the experimental group a decrease in the size of liver and spleen has been observed through palpatory evaluation by the end of the treatment course with pacovirin. In the the experimental group a positive dynamics of paraclinical indices (Alt, AST and γGTP) has been evident

The temperature dependence of hysteretic processes in Co nanowires arrays

In this paper, the temperature dependence of the hysteretic processes of Co nanowires, squarelly ordered in an array prepared by electrodeposition in nanopores of alumina membranes was analyzed. Both the magnetostatic interactions induced in the nanowires arrays and the thermal stresses (radial, azimuthal and axial stresses), which appear during the cooling of the system (nanowire and alumina template) from room temperature to 3 K was evaluated. The analysis of thermal induced stresses provides useful informations concerning the magnetic anisotropy in the Co nanowires. The temperature dependence of the remanent magnetization and coercitive field as an effect of the induced thermal stresses and magnetostatic interactions between nanowires was studied

Size Dependence of Static and Dynamic Magnetic Properties in Nanoscale Square Permalloy Antidot Arrays

Permalloy antidot arrays with different square hole sizes ( , , and ) have been fabricated by means of electron-beam lithography and lift-off techniques. The smaller square hole size results in enhanced remanence and reduced coercivity in the antidot array. Multiple resonance modes were clearly observed for the magnetic field applied normal to the array plane, and double uniform resonance modes occurred when the field deviated more than 30° from the normal to the plane. Two distinct dipolar field patterns with different orientations and magnitudes split the uniform resonance into double resonance modes. The double resonance modes show uniaxial in-plane anisotropy and the easy axes are orthogonal. The magnitude of the induced dipolar anisotropy remains almost constant with changes in the square hole size. The double resonance peaks move to low field with reduction of the square hole size