Part Of Ac Magnetic Susceptibility Research Articles

PEGylation of Co-Zn Ferrite Nanoparticles for Theranostics.

Multi-element ferrite nanoparticles (NPs) were synthesized as heat agents for use in magnetic hyperthermia treatments, specifically, Co0.8Zn0.2Fe₂O₄ NPs coating with polyethylene glycol. The crystal structures of these particles were examined by X-ray diffraction. Particle diameters were controlled to be approximately 10 nm by controlling the annealing temperature and time. The modification of polyethylene glycol (PEG) on the particles was confirmed by mass spectrometry and Fourier-transform infrared spectrometry. The heat dissipation characteristics of the particles were investigated by measuring AC magnetic susceptibility and temperature increase in AC magnetic fields. A peak in the imaginary part of AC magnetic susceptibility χ″ appeared, depending on the frequency. The value of χ″ was found to contribute to the effective heat dissipation according to the Neel relaxation system. The temperature increase of the particles was measured in AC magnetic fields of 64-146 Oe, with an observed temperature increase of ~10 K. Finally, to test the applications of these particles in theranostics, in vitro experiments using human breast cancer cells were conducted.

Oxygen Isotope Effect in Ordered PrBaMn<sub>2</sub>O<sub>6</sub>

The oxygen isotope effect in ordered half-doped manganite PrBaMn216-18O6 has been investigated. Real and imaginary parts of ac magnetic susceptibility, dc magnetization and magnetoresistance were measured at temperatures from 4.2 to 320 K in applied magnetic field up to 35 kOe. Substantial increase of charge ordering (CO) transition temperature TCO under oxygen isotope substitution 16O 18O and small decrease of ferromagnetic (FM) transition temperature TFM were found. Small systematic shift of ferromagnetic transition temperature in oxygen reduced manganite PrBaMn216 18O5 is also considered. The obtained results are compared with those observed in other manganites demonstrating the large isotope effect.

Oxygen Isotope Effect in Layered Manganites

The oxygen isotope effect in ceramic bilayer manganite (La1 zPrz)1.2Sr1.8Mn216 18O7 (z = 0, 0.3, 0.4, 0.6) has been investigated. Real and imaginary parts of ac magnetic susceptibility, dc magnetization and magnetoresistance were measured at temperatures from 4.2 to 320 K in applied magnetic field up to 40 kOe. Substantial decrease of ferromagnetic (FM) transition temperature TFM under oxygen isotope substitution 16O → 18O was found. This positive isotope effect amounts to more than 20 K. A number of additional transitions of ferromagnetic type were observed at T >170 K, which also depend on oxygen overall mass. The obtained results are compared with those observed in other manganites exhibiting the large isotope effect.

Dependence of AC susceptibility of polycrystalline RuSr 2GdCu 2O 8 superconductor on magnetic field amplitudes and frequencies

Systematic measurements of the AC magnetic susceptibility of polycrystalline RuSr 2GdCu 2O 8 (Ru-1212) samples are reported for various frequencies and magnetic field amplitudes. The study covered frequency range from 22 Hz to 12.5 kHz and field amplitudes between 0.5 and 25 G. The variation of the real part, χ ′, as well as, the imaginary part, χ ″, of AC susceptibility for Ru-1212 samples has been investigated as a function of temperature for different magnetic field amplitudes and frequencies. A qualitative analysis of AC susceptibility response for Ru-1212 superconductor near the transition temperature, T c, is presented. A single distinct peak in the imaginary part of AC magnetic susceptibility versus temperature is typically observed upon entering the superconducting state. The dependence of peak temperature, T p, of the χ ″ on magnetic field amplitude and frequency has been also investigated. It was found that the peak temperature, T p, is shifted to higher temperatures by increasing frequency and to lower temperatures by increasing magnetic fields.

Electrical and magnetic properties of Hg0.3Tl0.7Ba2Ca3Cu4O10+δ doped with Ni and Ag

Bulk superconducting samples of the type Hg0.3Tl0.7Ba2Ca3(Cu1−xRx)4O10+δ have been synthesized at normal pressure. The x-ray powder diffraction (XRD) for the prepared samples is studied and the lattice parameters ‘a’ and ‘c’ are calculated. The transition temperature Tc determined from both electrical resistance and ac magnetic susceptibility showed a decrease in its value by increasing both Ni and Ag contents. The electrical resistance data are measured at different applied magnetic fields which show that this field does not affect the first stage of the transition, while the transition width is enlarged by increasing the magnetic field. Critical current density, calculated from the imaginary part of ac magnetic susceptibility, is well fitted according to the formula Jc(T) = Jc(0){1 − T/Tc}γ.

Vortex dynamics in Bi 2(Sr,La) 2CuO 6+ δ and Bi 2Sr 2CaCu 2O 8+ δ single crystals with columnar defects

Vortex dynamics is studied in La-substituted Bi 2Sr 2CuO 6+ δ (Bi-2201) and Bi 2Sr 2CaCu 2O 8+ δ (Bi-2212) single crystals irradiated with 3.8 GeV 181 Ta 37+ ions through the relation between the frequency and the loss peak temperature in the temperature dependence of the imaginary part of AC magnetic susceptibility χ″. In unirradiated Bi-2201 and Bi-2212, the behavior of thermally activated flux flow or creep is observed. The Bose-glass behavior is observed at fields below the matching field B Φ in irradiated Bi-2212. On the other hand, the Bose-glass behavior is not observed in irradiated Bi-2201. This difference is due to the extremely weak coupling between pancake vortices along the c-axis in Bi-2201 even under the presence of columnar defects. The vortices in Bi-2201 irradiated with heavy ions are almost decoupled, resulting in the occurrence of thermally activated vortex creep.

Physical characteristics of imaginary ac magnetic susceptibility of granular superconductor, Hg0.69Pb0.31Ba2Ca2Cu3O8+δ

Temperature dependence of the imaginary part of ac magnetic susceptibility χ″ of Hg.69Pb.31Ba2Ca2Cu3O8+δ is investigated. We trace out the hysteresis loops at different temperatures for the experimental data of Hg.69Pb.31Ba2Ca2Cu3O8+δ. Furthermore, the external ac field has fully been penetrated into the specimen at the coupling temperature Tp(real), which is predicted by our theory, but with a slight temperature shift ΔTp from Tp(expected) at which the magnetic field have just penetrated into the centre of the specimen, i.e. Tp(real)Tp(expected).

Flux trapping and its effect on AC susceptibility of granular superconductors

Experimental data on the real (x′) and imaginary (x″) parts of AC magnetic susceptibility as a function of DC bias field (H) shows the effect of trapped flux in granular highT c superconductors. The aim was to substantiate our recent theoretical findings on the basis of a two-component critical state model suitable for granular highT c superconductors. Stress has been given to understanding the origin of hysteresis inx′(H) andx″(H). It was seen in the experimental data that above a certain value of DC field range irreversibility appears inx′(H) andx″(H) creating hysteresis like loops. Comparison of data with calculated loops shows good agreement.x′(H) andx″(H) curves show considerable asymmetry in presence of trapped flux.