ABSTRACT
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.
ABSTRACT
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 â 25 × 10-6, (2) amorphous Co68.18Fe4.32Si12.5B15 with nearly zero negative magnetostriction, λ â -1 × 10-7, and (3) nanocrystalline Fe73.5Si13.5B9Cu1Nb3 (FINEMET) with small positive magnetostriction, λ â 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).
ABSTRACT
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.
ABSTRACT
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.
