Motion Of Magnetic Domains Research Articles

Influence of current density on the magnetization process in active spin-valve elements

Simultaneous magnetoresistance measurements and observation of magnetic domain structures have been performed on active spin-valve elements by means of in situ experiments in a Lorentz transmission electron microscope. Two different spin-valve structures with NiFe and NiFe/Co sense layers have been studied with two sizes of rectangular elements. The effect of different applied current values has been analyzed and the addition of a Co layer in the sense layer has a large influence on the spin-valve behavior and on the domain structure. Also, two different processes for magnetic domain growth and motion have been observed for low or high applied current densities.

Magneto-Resistive Head For The High Recoring Density

The Magneto-Resistive Head (MR Head) are adopting to magnetic recording systems for its advantages, like as higher output voltage rather than the inductive thin film head and other reasons. Today, meny companies are manufacturing the MR Head, holding some difficulties. One of the most important thing for the manufacturer is the suppression of noise due to magnetic domain motion. In this paper, I would like to describe the over view of MR Head design and some difficulties for manufacturing.

Moving characteristics of magnetic domains in FeCrAl damping alloys

The dynamic observation of magnetic domain structure and motion of domain walls within ferrite in FeCrAl series ferromagnetic damping alloys were investigated using an in-situ technique in an electron microscope equipped with a tensile stage. Results showed that the motion of magnetic domain under external stress was accomplished through the disappearance of part prior domain walls, the formation of new walls and the reconfiguration of prior and new domain walls. The characteristics of magnetic domain motion within ferrite were preliminarily researched.

Freezing of magnetic domain motion in a reentrant spin glass as seen by elastic measurements

We report here measurements of elastic modulus of a reentrant spin glass (RSG) across the reentrant transition temperature ( T sg ). By measuring the Young modulus ( E) in a magnetic field we obtained the “Δ E” effect, which is the contribution of the ferromagnetic domains to the E. While a small but finite “Δ E” effect has been observed in the RSG below the first ferromagnetic transition temperature ( T c ), it vanishes for T < T sb . In contrast to the RSG, in a ferromagnet the “Δ E” effect is temperature independent at T ⪡ T c . We explained this observation as arising due to freezing of magnetic domain motion at or below T sg . This experiment in conjunction with previous magnetic experiments show that the observed “reentrant” transition is determined by freezing of domain motion.

Stroboscopic observation of domain motion on coated Si-Fe sheet using scanning electron microscope

A novel computer technique for visualizing the dynamic motion of magnetic domains at 64 consecutive points in a magnetic cycle is described. Requirements on strobing the SEM in order to build up video pictures of the dynamic motion are examined. It is found that the repeated slow motion display of the 50-Hz magnetization at a display rate which is matched to the analytical capability of the human eye-brain channel gives very good insight into the dynamics of domain nucleation, growth, and pinning in relation to the metallurgical features present.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Use of fiber waveguides for real-time laser photography of rapid motion of magnetic domains and domain walls

A description is given of a method for multiframe photographic recording of fast motion of domains and domain walls in real time. This method is based on the use of a train of light pulses delayed in time by fiber-optic waveguides of different lengths.

Effect of magnetic domains on the electrical resistivity of a ferromagnet just below the critical temperature

The motion of magnetic domains has been detected by measurements of the electrical resistivity temperature derivative in the vicinity of the critical temperature of various ferromagnetic systems. The case of TbZn serves as an illustration. A theoretical model is based on a mean field expression for the electrical resistivity.

Magnetic Relaxation Phenomena near TN in Co(HCOO)22H2O

The relaxation phenomena near T N in Co(HCOO) 2 2H 2 O have been studied by means of AC magnetic susceptibility with frequency of 7 Hz∼1 MHz. The relaxation phenomena which are due to the magnetic domain or the spin cluster motion have been detected clearly and studied. The relaxation effect of the magnetic domain motion can be separated out from the “intrinsic” susceptibility peak which comes from the phase transition, by applying the small external static magnetic field, and/or by using the relatively high frequency. The relaxation of the magnetic domain motion affects the “intrinsic” susceptibility of the phase transition even above the transition temperature. So called “critical slowing down” or “critical speeding up” in the crystal would have been observed in much higher frequency than 1 MHz.

On the limit velocity of magnetic domain and domain boundary motion in ferromagnets

A condition is obtained which limits the velocity of domain boundary motion. Analysis of this condition permitted the indication of examples of magnets in which the velocity of domain boundary motion can substantially exceed the Walker limit. It is shown that the limit velocities of domain boundaries can differ substantially with the collapse of the cylindrical domain and its translational motion.

Cylindrical magnetic domains

This review is devoted to a systematic exposition of theoretical and experimental results related to the physics of cylindrical magnetic domains (bubbles). The stability problem is discussed for an individual cylindrical domain and for a lattice of such domains, with allowance for the effect of the coercivity on the stability and dynamics of cylindrical domains. A detailed discussion is given of the laws of motion of cylindrical magnetic domains under the influence of inhomogeneities of magnetic field, temperature, and plate thickness. Phase transitions in a lattice of domains are considered, and the singularities of the magnetization and magnetic susceptibility in such phase transitions are determined. A theory is given for waves propagated in a lattice of domains. Detailed consideration is given to the effect of external factors and of the parameters of the magnetic material on the dynamical properties of a lattice of domains.

Overshoot in the translational motion of magnetic bubble domains

We report observations of overshoot in the motion of a bubble domain in a pulsed field gradient obtained by high-speed photography and by a technique which enables a photoelectric signal proportional to bubble translation to be derived. At high drive fields, a correlation between the amount of overshoot and the distance moved by the bubble during the field pulse has been observed. At low drive fields, some overshoot has been found to occur in a high-mobility LuGd film, but not in a low-mobility YSm sample.

Time-dependent translational velocity of magnetic bubble domains

The translational motion of magnetic bubble domains in a LuGdAlFe garnet film has been studied by high-speed photography. It was found that the average bubble velocity during a field gradient pulse is strongly dependent on the pulse duration τ, varying from 4200 cm/sec at τ=100 nsec to 1700 cm/sec at τ=500 nsec, at a field difference across the bubble diameter of 9.3 Oe. Large overshoots were observed at τ=500 nsec, but were greatly reduced at τ=100 nsec.

Steady-State Motion of Magnetic Domains

This paper introduces two integrals which simplify calculation of the dynamic properties of magnetic domains. These integrals, over quadratic functions of the spatial derivatives of the magnetization, yield forces acting on a domain which correspond to the gyroscopic and dissipative terms in the Gilbert equation. The force integral corresponging to the gyroscopic term is found to be even less sensitive to the details of the spin distribution than the dissipative drag integral. Hard magnetic bubble domains are considered as an illustrative example.

Defects in garnets suitable for magnetic bubble domain devices

A review of some of the defects that influence magnetic bubble domain motion is presented. The defects are catalogued and their origin and control are briefly discussed. A technique for staining defects by magnetic bubbles is described. The advantages of this technique over the stripe domain approach are listed. Examples of defects stained by the bubble raft technique are presented. The use of garnets for magnetic bubbles has stimulated a considerable amount of effort in understanding and eliminating magnetically active defects. Currently, the level of defects in films produced in this laboratory and elsewhere [1] range from a few to 102defects per square centimeter. In this brief note we review and catalog the nature of defects and the status of our understanding of the origin of defects in garnet substrates and films. We shall also consider the magnetic domain techniques used for staining defects in these materials. This review is limited to defects generated during and up to steps leading to film fabrication that are common to a variety of film growth techniques. It does not include details of defects which are uniquely characteristic of a particular technique. It also does not consider defects introduced during device fabrication such as the metallurgy of the overlay or improper design of the drive pattern.

High-speed stroboscopic analysis of a current-drive magnetic-domain propagating circuit

A high-speed optical stroboscopic system has been employed to examine the motion of magnetic domains in a current-drive propagating circuit used in conjunction with yttrium orthoferrite. Effects due to variations in the drive and bias fields and the frequency of propagation are observed in various parts of the circuit. The results are combined with the circuit and material parameters to yield a high-frequency propagation limit for the system and a qualitative understanding of the domain motion.