Submicron Magnetic Wire Research Articles

Depinning fields of a magnetic domain wall from asymmetric notches

Depinning fields of a magnetic domain wall (DW) from asymmetric notches artificially introduced into submicron magnetic wires were investigated by utilizing the giant magnetoresistance effect. It was found that the depinning field from the asymmetric notch depends on the propagation direction of the DW. The asymmetric notch works as an asymmetric potential barrier against the DW propagation. The depinning field increases with increasing slope of the asymmetric notch.

Propagation of a magnetic domain wall in magnetic wires with asymmetric notches

The propagation of a magnetic domain wall (DW) in a submicron magnetic wire consisting of a magnetic/nonmagnetic/magnetic trilayered structure with asymmetric notches was investigated by utilizing the giant magnetoresistance effect. The propagation direction of a DW was controlled by a pulsed local magnetic field, which nucleates the DW at one of the two ends of the wire. It was found that the depinning field of the DW from the notch depends on the propagation direction of the DW.

Temperature dependence of depinning fields in submicron magnetic wires with an artificial neck

Magnetization reversal in a submicron magnetic wire with an artificial neck consisting of a magnetic/nonmagnetic/magnetic trilayered structure was investigated by utilizing the giant magnetoresistance effect. A magnetic domain wall was pinned by the artificial neck introduced into the wire, which indicates that the neck works as a pinning center of the domain wall. The temperature dependence of the depinning field between 4.2 and 300K was described well by a theoretical model based on thermally assisted magnetization reversal over a single potential barrier. The magnitude of the potential barrier of the artificial neck was estimated.

Propagation velocity measurement of a magnetic domain wall in a submicron magnetic wire

The propagation velocity of a magnetic domain wall in a magnetic/nonmagnetic/magnetic trilayered wire with submicron width was investigated by utilizing the giant magnetoresistance effect. The magnetic domain wall was nucleated and injected into the magnetic wire by a pulsed local magnetic field (Hloc) applied at an end of the wire. This method using Hloc made it possible to determine the velocity as a function of an external magnetic field (Hext). It was found that the velocity is constant over a distance of 2 mm and that the mobility of the domain wall is constant in the temperature range between 4.2 and 200 K.

Onion‐Type Complexation Based on Carbon Nanorings and a Buckminsterfullerene

Manipulation of a magnetic state by a spin-polarized current is one of the exciting topics in solid state physics. We succeeded in driving a magnetic domain wall (DW) in magnetic nanowire by an electric current flowing through the wire. Figure 1 (a) shows a schematic illustration of a top view of a sample. One end of the L-shaped wire is connected to a diamond shaped pad which acts as a DW injector. A single DW can be introduced from the DW injector, and it stops in the hatched area. Figure 1 (b)-(f) shows the realspace observation of the current-driven DW motion by using the magnetic force microscopy (MFM). These are successive MFM images with one pulsed-current applied between Real-Space Observation of Current-Driven Domain Wall Motion in Submicron Magnetic Wires YAMAGUCHI Akinobu and NASU Saburo (Graduate School of Engineering Sience)

Propagation velocity measurement of a magnetic domain wall in a submicron magnetic wire

Abstract The propagation velocity of a magnetic domain wall in a magnetic/nonmagnetic/magnetic trilayered wire with submicron width was investigated by utilizing the giant magnetoresistance effect. The magnetic domain wall was nucleated and injected into the magnetic wire by a pulsed local magnetic field (H loc ) applied at an end of the wire. This method using H loc made it possible to determine the velocity as a function of an external magnetic field (H ext ) . It was found that the velocity is constant over a distance of 2 mm and that the mobility of the domain wall is constant in the temperature range between 4.2 and 200 K.

Dynamics of a magnetic domain wall in magnetic wires with an artificial neck

Magnetization reversal in submicron magnetic wires consisting of a NiFe/Cu/NiFe trilayer with an artificial neck was investigated by utilizing the giant magnetoresistance effect. A magnetic domain wall was injected into the wire by a local magnetic field applied at the end of the wire. Pinning and depinning of the magnetic domain wall were detected as sharp changes in resistance. It was found that the neck works as a pinning site of a domain wall and that the depinning field increases with a decrease of the neck width.

Magnetization reversal and electric transport in ferromagnetic nanowires

A method for magnetization reversal measurements in submicron magnetic wires was developed by utilizing the giant magnetoresistance effect, which enables us to determine a domain wall position as a function of time, and allows to evaluate the propagation velocity of the domain wall easily. It was found that the magnetization reversal in a wire occurs in association with the propagation of a single domain wall and that an artificial neck introduced into the wire acts as a pinning site of the magnetic domain wall. Injection of the magnetic domain wall from one end of the wire is demonstrated. Results on electric resistance measurements down to 20 mK for ultranarrow Ni wires are also presented. An increase of resistance proportional to T −1/2 was observed in a temperature range from 10 K to 80 mK. The result is discussed in terms of the electron–electron interaction and the weak localization effects.

Study of magnetization reversal in submicron wires using the giant magnetoresistance effect

Magnetization reversal phenomena in submicron magnetic wire systems were investigated from magnetoresistance measurements. Wire arrays and also single wire samples consisting of two magnetic layers with different coercivities were prepared and the resistivity was measured by applying external magnetic fields. Owing to the non-coupled type of giant magnetoresistance effect, the resistivity of wires is enhanced in proportion to the relative area of antiparallel magnetization. It is demonstrated that the resistivity measurements can sensitively detect the magnetization reversal phenomena in submicron wires. The dynamic properties of domain walls in wire samples are studied and the velocity of domain wall propagation is estimated.

Injection of a magnetic domain wall into a submicron magnetic wire

Two types of magnetic wires (150 nm width) with trilayer structure consisting of NiFe (20 nm)/Cu (20 nm)/Co (20 nm) were prepared. One was connected to a square pad (0.5×0.5 μm2) at one end, while the other has a symmetrical shape with two flat ends. Magnetization reversal was detected sensitively by magnetoresistance measurement. Switching field of the Co layer for the wire with a pad was much smaller than that for the wire without a pad. This indicates that a domain wall nucleates initially in the pad and is injected into the wire at the switching field. This model for the magnetization reversal process is supported by the angular dependence of the switching field.

GMR effect in a single trilayer wire with submicron width

Magnetization reversal phenomena in a submicron magnetic wire with a trilayer structure were investigated by measuring the electric resistance in external magnetic fields. The critical field for domain wall nucleation was observed to be slightly different for each field sweep. The magnetoresistance measurements were repeated 200 times with a sweep rate of 6 Oe/s. The obtained distribution of critical fields had two peaks and both moved to higher fields as temperature was decreased. This result suggests that domain wall nucleation occurs through a thermally activated process down to 5 K.

Propagation of the magnetic domain wall in submicron magnetic wire investigated by using giant magnetoresistance effect

The magnetization reversal phenomenon in a submicron magnetic wire with a trilayer structure consisting of NiFe(400 Å)/Cu(200 Å)/NiFe(50 Å) was investigated by measuring the electric resistance in external magnetic fields. It is shown that the magnetization reversal can be very sensitively investigated by utilizing the giant magnetoresistance effect. The time variation of resistance during the magnetization reversal was also measured and the velocity of the magnetic domain wall propagating in the wire was determined at 77 K.

Magnetization reversal in submicron magnetic wire studied by using giant magnetoresistance effect

The magnetization reversal phenomenon in a submicron magnetic wire with a trilayer structure consisting of NiFe(200 Å)/Cu(100 Å)/NiFe(50 Å) was investigated by measuring the electric resistance in an external magnetic field. A giant magnetoresistance (GMR) effect of about 0.8% was observed when the magnetizations in two NiFe layers are oriented antiparallel. It is demonstrated that magnetization reversal phenomena can be very sensitively investigated by utilizing the GMR effect.

Magnetic and Transport Properties of Micron Size Magnetic Participate Arrays Fabricated on a 2D Superconducting Nb Films and Sub-Micron Magnetic Wires

ABSTRACTMicron size particulate arrays of amorphous R-Co (R = Sm and Gd) alloys with a thickness of 200 nm were fabricated on top of a 20 nm thick Nb film by means of e-beam lithography and sputter deposition. The arrays consist of 2 × 2 μm2 square particles with a spatial periodicity of 4 μm along an edge of the square. Interesting oscillations due to the fluxoid quantization were observed both in the transition lines and the magnetization curves of the underlying Nb film. The superconducting state of the Nb film was found to be modulated by stray fields of the square magnetic particles.Sub-micron size ferromagnetic Fe wires were also prepared in order to investigate the magnetoresistance effect associated with pinning and depinning processes of a magnetic domain wall confined in the wire. Low temperature transport, Lorentz microscopy and electron holography measurements demonstrated a clear change in resistivity associated with the depinning of a pinned single domain wall.