L.V. Hong

Invitro toxicity test and searching the possibility of cancer cell line extermination by magnetic heating with using Fe3O4 magnetic fluid

A Fe3O4 based magnetic fluid with different concentrations ranged between 0.15 ng/cell to 10 ng/cell (nano gram/cell) was used in the in vitro toxicity test on several cancer cell lines, Sarcoma 180, HeLa and H358. It shows that the fluid with a concentration of Fe3O4 below 1.2 ng/cell is completely non-toxic for these cell lines. Even through in the presence of the highest concentration of 10 ng/cell, the cell viability still reaches more than 60%. The magnetic fluid with Fe3O4 concentration of about 0.1 ng/cell was also used to search ex-vivo the possibility of Sarcoma 180 extermination by magnetic heating with an AC field of 120Oe and 184 KHz. The result shows that after a heat treatment for 30 min., 40% of Sarcoma 180 cells was killed.

Tunnelling mafnetoresistance of (1 – x)La0.7Ca0.3MnO3 +xAg composites

Magnetization and transport of (1 – x)La0.7Ca0.3MnO3 +xAg (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) composites has been reported in this paper. Low Field Magnetoresistance (LFMR), conductivity (σ) and metal – insulator transition temperature (Tp) increases with increasing content of Ag. Due to the presence of nomagnetic Ag in the ferromagnetic La0.7Ca0.3MnO3 material, dc magnetization decreases but the corresponding Tp increases. Based on the spin polarized transport of conduction electrons at the grains boundaries, we find that our experimental data (MR – H) agree quite well with the dependence of temperature on tunneling magnetoresistance (TMR) described by an expression of Hwang et al.

Magnetic memory effect in a strong phase competition system La0.7Ca0.3Mn0.925Ti0.075O3

A magnetic memory effect was observed by means of zero-field-cooled magnetization measurements in a temperature range below TC. The magnitude of magnetic memory effect, determined by the difference between the magnetization curve with a pause of temperature during the cooling process and its reference curve without the pause, showed that it is independent of the number of pauses. The memory effect is supposed to be related to the isolated states with an infinite degeneration, which is associated with the presence of magnetic frustration in a system with a strong magnetic phase competition. Besides, a resistance memory effect was concomitantly observed at the same pause temperatures.

Demonstrate the Double Negative Behavior of Metamaterial Using the Effective Medium Theory

We fabricated the electric and magnetic metamaterial, and measured their transmission spectra. The electromagnetic response of the combined structure, which consists of cut-wire pair and continuous wire, are experimentally and numerically studied in the microwave frequency regime. The simulations are performed in a qualitative agreement with experiment utilizing the transfer-matrix method. The double negative behavior of combined structure is observed and demonstrated using the effective medium theory.

Metamaterials: Detailed parametric studies on cut-wire pair and combined structure

We studied the electromagnetic behavior of cut-wire pair structure, which is considered as a magnetic metamaterial for designing the left-handed material. It was found that the lattice constant of cut-wire pair structure provides subtle effects not only on the electric resonance but also on the magnetic one. In addition, we also investigated on how this affects the left-handed behavior of combined structures of cut-wire pair and continuous wire. These structures were designed, fabricated, and measured in the microwave frequency regime.

CIP spin torque effect in the spin valve pinned with an oxide antiferromagnetic layer

Spin valve Ni0.85Co0.15O/Co85Fe15/Cu/Co85Fe15 was manufactured by a RF magnetron sputtering system. M(H) and R(H) characteristics of the spin valve were measured in CIP configuration at room temperature has a magnetoresistance ratio of about 8% and a high exchange bias at room temperature. The current density and angle between the applied magnetic field and injection current were changed in an aim to observe their effects on MR and exchange bias of the spin valve. The current density and angle strongly affect MR and exchange bias. Both MR and exchange bias clearly decrease in dependence of the current density and direction of the magnetic field. It is supposed to be related with a current-induced spin torque in device.

Effect of the Coating Speed on Dipole Relaxation Time in the YMnO3 Thin Films

ABSTRACT YMnO3 thin films were prepared by the dip coating technique from the solution with different coating speeds. One Debye relaxation time process was used to analyze the frequency dependence of the experimentally given dielectric constant. Analyzing experimental data showed that the dipole relaxation process in the materials exhibits a complex relaxation process distorted off the Debye type with parameter β of about 0.8. The modified Cole-Davidson model has been used to fit the experimental data for whole frequency range up to 0.3 MHz. Based on the Cole-Davidson plots the relaxation time of these films has been estimated. The relaxation time decreases with an increasing the coating speeds, which are related with surface states.