Direct observation of magnetic domain walls in glass-coated submicronic amorphous wires.

Results on the magnetic domain walls in rapidly solidified magnetostrictive and non-magnetostrictive amorphous submicronic wires are reported. Utilizing Lorentz transmission electron microscopy (LTEM) for the first time in this context, we have visualized and analyzed the domain walls in such ultra-thin amorphous wires. All the investigated samples display vortex magnetic domain walls, regardless of wire composition or diameter. In non-magnetostrictive wires, the domain walls maintain their structure and symmetry under varying magnetic field conditions. In contrast, magnetostrictive wires show an elongation of their domain walls upon magnetic field application, a response linked to the magnetoelastic coupling between magnetostriction and internal stresses induced during wire preparation. This study advances the understanding of magnetization reversal processes in amorphous submicronic wires. The insights gained are crucial for future developments in miniaturized magnetic devices.

Field and Current Controlled Domain Wall Propagation in Twisted Glass-Coated Magnetic Microwires.

The torsion effect on the field and current driven magnetization reversal and the associated domain wall velocity in cylindrical amorphous and nanocrystalline glass-coated microwires is reported. Samples from three representative compositions have been investigated: (1) amorphous Fe77.5Si7.5B15 with positive magnetostriction, λ ≅ 25 × 10-6, (2) amorphous Co68.18Fe4.32Si12.5B15 with nearly zero negative magnetostriction, λ ≅ -1 × 10-7, and (3) nanocrystalline Fe73.5Si13.5B9Cu1Nb3 (FINEMET) with small positive magnetostriction, λ ≅ 2.1 × 10-6, all having the diameter of the metallic nucleus, d, of 20 µm and the glass coating thickness, tg, of 11 µm. The results are explained through a phenomenological interpretation of the effects of applied torque on the anisotropy axes within the microwires with different characteristics. Among all the complex mechanical deformations caused by the application of torque on magnetic microwire samples, the most important are the axial compression - for axial field-driven domain wall motion, and the circumferential tension - for electrical current/circumferential field-driven domain wall motion. The Co68.18Fe4.32Si12.5B15 microwire, annealed at 300 °C for 1 hour and twisted at 168 Rad/m exhibits the optimum characteristics, e.g. the lowest switching current (down to 9 mA~2.9 × 10-3 A/cm2) and the largest domain wall velocity (up to 2300 m/s).

Fe-Cr-Nb-B ferromagnetic particles with shape anisotropy for cancer cell destruction by magneto-mechanical actuation.

We introduce a new type of magnetic particles (MPs) prepared by wet milling of superferromagnetic Fe-Cr-Nb-B precursor glassy ribbons for cancer treatment by magneto-mechanical actuation in low magnetic fields (1 ÷ 20 Oe). The rectangular shapes of MPs and the superferromagnetism of the glassy alloys of which are made the MPs induce important magnetic shape anisotropies which, in association with a large saturation magnetization, generate an improved torque in a rotating magnetic field, producing important damages on the cellular viability of MG-63 human osteosarcoma (HOS) cells. The specific parameters such as MPs concentration, frequency and intensity of the applied magnetic field, or the time of exposure have a strong influence on the cancer cells viability. The specific behavior of the Fe-Cr-Nb-B MPs offers them destructive effect even in low magnetic fields such as 10 Oe, and this characteristic allows the use of coils systems which provide large experimental spaces. The novel MPs are used for the magneto-mechanical actuation alone or in association with hyperthermia, but also can be transported to the tumor sites by means of stem cells carriers.

Simultaneous magneto-optical Kerr effect and Sixtus-Tonks method for analyzing the shape of propagating domain walls in ultrathin magnetic wires.

The controlled nucleation and propagation of magnetic domain walls in ultrathin ferromagnetic wires, such as nanowires and submicrometer wires, is extremely important for the development of new high performance magnetic domain wall logic devices. Therefore, it is equally essential to possess adequate advanced experimental investigation techniques in order to be able to achieve a comprehensive in situ analysis of as many as possible parameters related to the domain wall propagation, e.g., wall shape besides wall velocity and position. In this paper, we report on a method developed specifically for the investigation of the shape of propagating magnetic domain walls in ultrathin magnetic wires, i.e., with the diameter of the magnetic wire in the range 100-950 nm. The newly developed experimental method is based on the simultaneous use of two full-fledged experimental techniques: the magneto-optical Kerr effect for analyzing the surface effects of the passing domain wall and the Sixtus-Tonks method for the investigation of the entire moving wall. The results obtained offer essential information about the shape of the propagating magnetic domain walls, being unique to this new method.

Omni-directional selective shielding material based on amorphous glass coated microwires.

The shielding effectiveness of the omni-directional selective shielding material based on CoFe-glass coated amorphous wires in 0.8 GHz-3 GHz microwave frequency range is investigated. The measurements were done in a controlled medium using a TEM cell and in the free space using horn antennas, respectively. Experimental results indicate that the composite shielding material can be developed with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires.

Accurate measurement of domain wall velocity in amorphous microwires, submicron wires, and nanowires.

A new method for measuring the domain wall velocity in a single, ultrathin ferromagnetic amorphous wire with the diameter down to 100 nm is presented. The method has been developed in order to increase the sensitivity in studying the domain wall propagation in bistable magnetic wires in a wide range of field amplitudes, with much larger values of the applied field as compared to those employed when studying the wall propagation in typical amorphous microwires. The large fields required to propagate the domain walls in ultrathin wires are able to nucleate new domain walls in the samples and, therefore, they can affect the accuracy of the entire measurement. The proposed experimental setup prevents such situations by using a number of complex pick-up coils, which allow the detection of the direction of the wall propagation along with the precise measurement of the domain wall velocity. The newly developed method is especially important now, when large effort is devoted to the development of domain wall logic devices based on ultrathin magnetic wires and nanowires.

[SEM comparative analysis of the composite diacrylic resin-enamel interface in laser and bur prepared cavities]. / Studiu de analiza comparativa SEM a interfetei rasina diacrilica compozita-smalt in cavitati preparate mecanic si kinetic cu laser.

UNLABELLED: The aim of this study was to demonstrate that the size of the hybrid layer (HL) in the prepared enamel mechanic (M) and kinetic (K) with laser (WaterlaseMDBiolase), evaluated by scanning electron microscopy (SEM) restored with two types of resin composite is different. MATERIAL AND METHOD: The study was realized in vitro on a sample of 40 extracted human premolar and molars teeth for orthodontic or periodontal reasons. The teeth were divided at random into equal four groups (Gr). There has been Class I cavities with a depth of 2 mm (M) at high and low speed with cylindrical diamond No.1 and globular carbide and (K) peaks MZ6-5, 5W+20 Hz 30% water 60% air. The teeth were restored using 3M Schotchbond Etch, 3M Single Bond Dental Adhesive System: Gr. 1: (K)(n = 10)-3M Filtekflow; Gr.2 : (K)(n = 10)3M FiltekZ250; Gr.3: (M)(n = 10)3M Filtekflow; Gr.4: (M)(n = 10)3M FiltekZ250. The materials were placed in a single layer and photoactivate source LED SmartLite (Dentsply), termocycling 500 cycles (5 degrees-55 degrees), stored (48h), cut lengthwise (diamond), polished, conditioned (H3PO4-37% -5s) analyzed by SEM (JEOLJSM 6390), SPSS 13.00 statistically analyzed (ANOVA, p = 0.05). RESULTS: Analysis of the (HL) has highlighted differences between groups p = 0.05 average size (HL) being Gr.1;20.80 (+/- 0.72)microm, Gr.2;4.034 (+/- 0.0076)microm, Gr.3, 14.13 (+/- 0.63)microm, Gr.4, 1,43 (+/- 0.16)microm. Value size (HL) was influenced by the cavity preparation method for samples prepared by laser p = 0,005 in terms of size and in advantage of mechanical preparations in terms of quality (HL). Also the value of (HL) size was influenced by the type of material used in advance Gr.2 p = 0.0017. CONCLUSIONS: The sealing of cavity depends more on the creep of materials and less on the type of preparation. Permission was obtained from a institutional ethical committee of "Gr.T. Popa" University of Medicine and Pharmacy Iasi and that subjects gave written, informed consent).