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The stray field magnitude and distribution, at sensor level, have been investigated as a function of the thickness of the shield, the presence of a domain wall in the shield, the relative position of the vortex accompanying the wall and its proximity to the Air-Bearing-Surface (ABS). Using micromagnetics, the stray fields at the reader sensor have been simulated while a domain wall moves in a shield near the ABS in a magnetic head. For shield thicknesses from 640 nm to 1280 nm, a range of interest for head design, the domain wall shape is C-shaped with a vortex-like structure on either side of the domain wall that provides flux closure inside the film. For a 5 Oe incidental field, the wall exits at the ABS in less than 20 ns when the wall is between the ABS and the vortex. Average stray fields reached 60 Oe while 100 Oe localized stray fields are observed as the wall exits the ABS. The dynamics of wall motion change when the vortex is between the ABS and the domain wall. A 5 Oe incidental field in a 640 nm thick shield drove the wall toward the ABS, compressing the vortex and creating a blocking structure. An incidental 10 Oe field twisted the wall center magnetization enough to change wall chirality accelerating the wall exit, preventing the blocking structure, and flipping the vortex to the other side of the wall. Average stray fields are 55 Oe with a local maximum of 70 Oe. Similar results occur for a 1280 nm thick shield for a 5 Oe field, with average stray fields of 60 Oe and a local maximum of 100 Oe.

Cross-tie walls in permalloy films have been simulated as a function of thickness in the range 10-70 nm using direct integration of the Landau-Lifshitz-Gilbert equation in a Cartesian lattice with periodic boundary conditions along the length of the wall. A cross-tie wall is a Bloch-like transition along the wall [or vertical Bloch line (VBL)] between Neel Walls of opposite chirality in a film with in-plane magnetization. This transition is a low-energy state, which allows the long tails of Neel walls to partially close their magnetic flux in the vicinity of the walls. The magnetization configuration of these transitions is either elliptical (vortex) or hyperbolic (antivortex). The pi-VBL transitions are 50 nm in diameter and the distance from each other increases with film thickness. The cross-tie wall energy per unit area was lower than that of a pure Neel or Bloch wall between 15 and 50 nm film thickness.

Three-dimensional magnetic structures of pi-vertical-Bloch line (VBL) and 2pi-VBL are investigated in 80–320-nm-thick Permalloy films using direct integration of the Landau–Lifshitz–Gilbert equation in an 128×128×80 point Cartesian lattice. A pi-VBL reflects the shapes of its adjacent walls, which change with film thickness. The pi-VBL conducts the flux between walls of opposite chirality by letting the magnetization rotate out of the plane of the walls via a vortex structure. The Neel caps switch chirality via a “converging point,” or cross-tie, flux at one surface and a vortex flux, or a swirl, at the other surface. The pi-VBL energy per unit area is 0.44, 0.20, and 0.30 erg/cm2 in 80, 160, and 320 nm films, respectively. The corresponding pi-VBL widths are 88, 60, and 86 nm. A stable winding 2pi-VBL structure was also computed by combining two pi-VBL structures of appropriate chirality. The Neel caps intersect via the pair-(swirl, converging point) like flux at both surfaces. The width of the 2pi-VBL i...

The Bloch to Neel wall transition is investigated in Permalloy films between 160 and 10 nm thickness using direct integration of the Landau–Lifshitz–Gilbert equation in a three-dimensional Cartesian lattice. At 80 nm, the wall is a symmetric Bloch wall characterized by two adjoining vortices with the magnetization at the wall center pointing perpendicular to the plane of the material throughout the thickness. The Bloch to Neel transition takes place between 35 and 30 nm, below which the wall becomes a symmetric Neel wall. For the Bloch walls, our wall energy per unit area calculations match reasonably well the results of A. Hubert’s Ritz method calculations [Magnetic Domains (Springer, New York, 1998), p. 251] and A. E. Labonte’s numerical calculations [J. Appl. Phys. 40, 2450 (1969)]. For the Neel walls, however, our results indicate an approximately 70% higher energy for thicknesses of 30 nm and below, since the Neel wall tails are included. For thicknesses below 160 nm, the anisotropy energy component ...

Topological patterning of magnetic thin films has a substantial effect on domain behavior. Bubble domains located underneath a groove in patterned material display an ovoid profile with the major axis along the groove. The major axis was measured to have a diameter up to twice that along the minor axis. Measurements of the collapse field indicate that it can vary by up to 3% with changes in the groove depth, and by up to 5% with changes in the pitch of a groove array.

The transitional wall structure of a domain wall in Permalloy films in the thickness range of 5.12 /spl mu/m to 0.16 /spl mu/m is investigated using direct integration of the Landau-Lifshitz-Gilbert equation in a three dimensional Cartesian lattice. The expected stray-field-free structure containing a Bloch wall in the center, Neel caps at the surfaces with a vortex structure on one side of the wall was found for films thicker than 2.56 /spl mu/m. However, the region through the thickness where the /spl nabla//sup /spl omega///spl middot/M/sup /spl mu// across the wall is zero (Bloch wall) was of small extent below 1 /spl mu/m thickness. Neel caps with opposite chirality existed at all thickness investigated down to 0.16 /spl mu/m. The vortex is characterized by an overshoot in the polar angle /spl theta/ out of the plane of the material. Two maximum values of the overshoot were observed for films 2.56 /spl mu/m and thicker. They were located near the film surface under the Neel caps. Thinner films had only one maximum located in the center of the material. The maximum overshoot was a function of thickness varying from 100 to a maximum value of 340 for the 0.64 /spl mu/m thick sample. As the thickness is decreased to 0.16 /spl mu/m, a residual normal component is observed at the surface near the Neel caps, leading to stray fields at the surface.

Annealing short very low magnetostriction amorphous ribbons in the demagnetized state results in a Perminvar-like reentrant hysteresis loop due to domain wall stabilization by the induced anisotropy. After a hard saturation, the loop changes to that of an unprocessed ribbon. In this investigation, ribbons are annealed in the demagnetized state with one wall along the ribbon middle. This wall becomes pinned during the heat treatment. Reentrant reversal occurs when reverse domains are nucleated at the ribbon edge with a threshold field larger than the demagnetizing field, this wall does not annihilate when it meets the pinned wall but leaves a line of reverse domains stabilized by ripple in the anisotropy. These domains enable a regular smooth reversal for the demagnetization process until the ribbon returns to the pinned configuration. The regular loop appears when the ribbon has been completely saturated by a large field. Mobile walls are nucleated on both sides of the pinned wall so that the ribbon does not return to the pinned configuration. Reversal now follows the usual demagnetization curve over the entire cycle. Kerr magnetooptical domain and domain wall observations are used in this investigation. All of the possible wall structures predicted by the model of asymmetric flux closed Bloch walls were identified.

The dynamic behavior of an isolated stripe domain attracted to a single rectangular groove on the top surface of a 1.6-μm-thick bubble garnet film is analyzed using a numerical model based on the Landau–Lifshitz–Gilbert equation. The groove creates an effective field which interacts with the stripe domain, such that the azimuthal angle of magnetization in the wall no longer rotates uniformly through the film thickness. The wall shape becomes highly distorted near the groove, forming head-on walls at the groove corners, and cleaving when pushed beneath the groove.

In this study, we investigate the change in the magnetic properties of magnetostrictive Fe/sub 77.5/Si/sub 7.5/B/sub 15/ amorphous wires thinned by chemical etching focusing on domain structure. It is found that the re-entrant flux reversal characteristic is still maintained even in the wire chemically thinned to a diameter of 27 /spl mu/m. The maze domain is observed on the wire thinned to a diameter of around 80 /spl mu/m. Below this diameter, the wire shows bamboo domains. When thinned below 42 /spl mu/m, the wire shows the single domain. The drastic change in the domain configuration due to thinning is explained by considering the very low anisotropy in the thinned wire caused by the decrease of anisotropy due to the etching of the outer shell. It is confirmed that the domain structure of the as-quenched 65 /spl mu/m wire is quite different from that of the wire thinned to the same diameter.

In this work we have studied the behavior of the bamboo domains under stress (/spl sigma/), tension (+/spl sigma/) as well as compression (-/spl sigma/), with the aim of making the domain model of the negatively magnetostrictive (-/spl lambda//sub 2/) CoSiB wire clear. It Is observed that the growth of the surface bamboo domains due to /spl sigma/ has directivity depending on the orientation of the underlying core domain. In one orientation the black bamboo domain grows, while in the opposite orientation the white domain grows. From the stress behavior of the bamboo domains we have concluded that the domain model of -/spl lambda/, wire consists of two spiral domains of opposite rotation and we propose a new model.

To get a deeper insight into the mechanism involved in the flux reversal of Co based wire we have tickled the wire with an ac field of smaller amplitude than the switching field, H*, and observed the signal induced in a pancake coil moved along the wire, vibrated a small coil along the wire and observed the induced signal, and taken the temperature dependence of normalized saturation magnetization, Ms, and H*. No signal was observed in the pancake coil in the tickling experiment. A signal that has peak values close to the wire ends, but practically zero in the central region, was observed in the vibrating coil. The variations of Ms and H* with temperature only show a correlation. The results of the above experiments suggest that for Co based wire the most reasonable mechanism for the flux switching is nucleation of a free wall other than the depinning of residual reverse domains at the wire ends.

The dynamics of a single threedimensional 2nWL structure in a domain have been investigated using large scale numerical simulations. The simulations were performed by solving the Landau-Lifshitz-Gilbert equation numerically in an xyz Cartesian lattice with 32x256~32 grid points. At each grid point, the simulation takes as input a characterization of the phenomenological magnetic parameters of exchange, anisotropy, magnetostatic interactions, and saturation magnetization, together with an initial magnetization distribution and prescribed external field. The simulations are performed on the Connection machine CM5. The width of a single 2xWL structure has been measured previously to be 0.59 pm[l]. Subsequent results to be presented here allow a more detailed analysis of the wall microdeformation due to the presence of the 2nVBL structure. A Lateral wall tilt of 418 A was measured in a direction perpendicular to the wall. It is 60% less than the wall tilt due to a single nVBL and about 70% smaller than those of a 2xvBL periodic chain[2]. The longitudinal microdeformation at half maximum is 1.22pm or twice the 2WBL width. A 30

Co-Fe-Si-B films have been prepared using a roll coater and DC magnetron sputtering system onto a polyethylene terephthalate substrate. This thin film exhibited an excellent uniaxial anisotropy introduced by an asymmetric thermal shrinkage of the substrate. Reversal with a single large Barkhausen pulse has been observed in thin film structure 1 mm by 50 mm by 0.65 /spl mu/m. Closure domains have been clearly identified at the film ends. The threshold for the reversal is the coercive force. The reason for reversal with a single Barkhausen jump is that the long narrow film geometry has essentially zero demagnetizing field over most of the film. Once the walls start to move through the center portion of the film, there is nothing to stop them so the reversal proceeds with a single large Barkhausen pulse.

The dependence of the magnetic properties of amorphous wire on the diameter have been investigated. The anisotropy constant, hence the internal stress, of the wire increases with the wire diameter. The size of the pinned reverse domain at the wire end increases with the wire diameter. Domain observation shows that irrespective of the change in the wire diameter, the domain structure basically consists of chevron domain layer sandwiched between the surface maze domain and the inner core domain.

Magnitudes and distributions of stray magnetic fields from a single domain wall in a Permalloy film are calculated for film thickness from 10 nm to 2.5 /spl mu/m, using direct integration of the Landau-Lifshitz-Gilbert equation in a Cartesian lattice. This thickness range supports a Neel wall whose magnetization rotates in the plane of the film, a symmetric Bloch wall whose magnetization rotates out of the plane, and an asymmetric Bloch wall whose magnetization rotates simultaneously in and out of the plane of the film at the surfaces and inside the film, respectively. The stray field magnitude is largest for films with a Neel wall rather than film with a Bloch wall. The stray field magnitude varies linearly with thickness for films with Neel walls. The field distribution has a Neel-dominant character, i.e., it lies in a plane perpendicular to the plane of the wall, parallel to the plane of the film, and is dominated by the transverse component of the field. For films with a Bloch-type component, the stray field is lower. The field distribution has a Bloch-dominant character, i.e., it lies in a plane perpendicular to the plane of the wall, normal to the plane of film, and is dominated by the normal component of the field. At thickness larger than 1 /spl mu/m, the stray field appears independent of thickness and is relatively constant at 15 Oe.

Magnetic properties and domain structure were investigated for die-drawn and subsequently annealed Fe-Si-B amorphous wires. It was found that the die-drawn wire has a bamboo domain similar to that of the Co based wire with negative magnetostriction and looses the re-entrant flux reversal characteristic. It was also found that the wire recovers the re-entrant characteristic after annealing. The tension-annealed wire has clear shell and core domain structure and exhibits the re-entrant characteristic with enhanced remanence. The surface bamboo domain layer as thin as 5 /spl mu/m was connected to the core domain by magnetization that changes direction continuously between two domains without a domain wall. From the temperature dependence of a threshold field for the discontinuous flux jump, it is inferred that the re-entrant characteristic is caused by the depinning of the reverse domain existing near the wire end due to demagnetizing effect.

Thin films of FeC were deposited onto a polymer substrate by reactive DC magnetron sputtering, using an argon and hydrocarbon gas mixture. The polymer web is wound by a roll coater, and an individual thin film with a constant thickness is piled up by increasing a number of passes UP to a desired thickness. Uniaxial films with Hk=4000 A/m and low dispersion were obtained. The coercive force was a function of thickness; it was Hc=8 A/m for films 0.8 /spl mu/m thick. The easy axis of the uniaxial anisotropy was along the direction transverse to the rolling direction of the polymer web. The origin of the uniaxial anisotropy is the anisotropic thermal shrinkage of the polymer web is discussed by a model.

Summary form only given. Cross-tie walls in Permalloy films have been calculated as a function of thickness at 25, 35, 40 and 45 nanometers (nm) using direct integration of the Landau-Lifshitz-Gilbert equation in a Cartesian lattice with periodic boundary conditions along the length of the wall (y-direction). Previously, the Bloch-to-Neel wall transition was found around 35 nm in a study where the two-dimensional (2D) Neel and Bloch walls were considered separately. The present work is extended to a 3D transition, a Bloch-like transition along the wall (or Vertical Bloch Lines (VBLs)), between Neel walls of opposite chirality in a film with in-plane magnetization. This 3D transition is a cross-tie wall, a low energy state, which allows for the long tails of Neel walls to close magnetic flux in the vicinity of the walls.

Stress changes the domain structure in magnetostrictive materials and consequently changes the magnetization. From this, one can imagine possible sensor applications based on the stress-magnetic effect of the wires. In this work, the authors have studied the stress-magnetic characteristics of amorphous wires and subsequently proposed possible applications for the wires based on the stress-magnetic effect. The proposed possible applications are, for instance, sensing of angle of rotation, direction of rotation and sensing of magnitude of torque.

Damping has a large effect on the dynamic character of domain walls in garnet material with structure within the walls. When a step change in bias field is applied to a wall containing a /spl pi/VBL chain or a 2/spl pi/VBL chain, the VBL velocity makes large changes in magnitude for the first 50 nsec when the damping is 0.1 and smoothly changes when the damping is 0.5. Dynamic distortion of 2/spl pi/VBL also makes large swings in magnitude for low damping. Because the wall and VBL velocity as well as 2/spl pi/VBL distortion change so markedly with time for low damping, it is clear that an increase in damping above the traditional /spl alpha/=0.1 is very desirable for material used in a VBL memory. >

The mechanism of re-entrant flux reversal in Fe-Si-B amorphous wires is investigated by domain observation and reverse domain detection focusing on the magnetic properties near the wire ends. It is found that the wire consists of shell and core domains and that the core region has the residual reversing domain due to the demagnetizing field near wire ends in a remanent state. The residual domain is stabilized by forming a flux closure structure through the shell domain. This increases the threshold field for domain growth to a value much larger than the wall coercivity and results in predominantly re-entrant flux reversal. >

The dynamics of a magnetic domain wall containing vertical Bloch line winding pairs (2 pi VBL) are numerically investigated. The wall is of the kind found in thin film materials with a large anisotropy perpendicular to the plane of the film. The 2 pi VBLs are all of the same chirality and are periodically repeated along the wall at equal spacing. The wall is driven by an applied field perpendicular to the film plane, and the VBLs move gyrotropically. Starting from an equilibrium shape, the 2 pi VBLs distort. If the field is low enough, a new dynamic shape is established that is quite stable. Above a threshold, the distortion pulls the 2 pi VBLs apart into a pi VBL chain before the dynamic equilibrium structure is established. This breakup is accompanied by a discontinuous jump in both wall and VBL mobility. >

The dynamic structure of a magnetic domain wall in a stripe compression experiment is investigated by numerical investigation of the Landau-Lifshitz-Gilbert equation. Domain walls of the type found in thin films with a large uniaxial anisotropy perpendicular to the plane of the material are considered. It is found that a single horizontal Bloch line (HBL) is formed in the domain wall and is responsible for wall overshoot and saturation of the wall velocity. These results compare favorably with experimental data. >

A sampling optical microscope is integrated with computer controlled instrumentation and a digital image processor. The system is used to make quantitative measurement of magnetic domain wall motion. The system can measure the average stripe width, over an 8.7 mu m length, with 0.003 mu m precision and 2 ns temporal resolution. With this system, the threshold for horizontal Bloch line (HBL) nucleation and the coercivity of a vertical Bloch line (VBL) is measured in straight walls in bubble garnet material. >

Domain observations were made on Fe- and Co-based amorphous magnetic wires that exhibit a large Barkhausen discontinuity during flux reversal. Domain patterns observed on the wire surface were compared with those found on a polished section through the center of the wire. It was found that the Fe-based wire consists of a shell and core region with a third region between them. This fairly thick transition region made up of domains at an angle of about 45 degrees to the wire axis lacks the closure domains of the previous model. The Co-based wire does not have a clear core and shell domain structure. The center of the wire has a classic domain structure expected of uniaxial anisotropy with the easy axis normal to the wire axis. When a model for the residual stress quenched-in during cooling of large Fe bars is applied to the wire, the expected anisotropy is consistent with the domain patterns in the Fe-based wire. >

A new distance sensor utilizing stepwise domain wall propagation caused by a pulse wire current train in a twisted magnetostrictive amorphous wire is presented. A 1000-mm long digital distance sensor having a nonlinearity of 0.5% FS and a simple construction is realized. The sensor characteristics are controlled by applying torsion. The stepwise domain wall propagation characteristics are compared with those for a steady state domain wall propagation. >

The dynamics of a magnetic domain wall containing vertical Bloch lines (VBLs) has been investigated using numerical methods. The wall is of the kind found in thin-film materials with a large anisotropy perpendicular to the plane of the film. The VBLs are all of the same chirality and are periodically repeated along the wall at equal spacing. The wall is driven by an applied field perpendicular to the film plane and the VBLs move gyrotropically. Both the wall and VBLs, starting from an equilibrium shape, soon attain a constant velocity. Distortion of the wall and structure from the equilibrium shape is evident and increases with field. The wall and VBL velocity both increase with field but neither are linear so that the ratio of VBL velocity to wall velocity decreases with applied field. For an applied field extrapolated to zero, the wall velocity agrees with the value predicted by the analytical rigid wall model and the ratio decreases by 50% for higher fields because of the distortion. >

Domain wall processes (domain wall configuration, propagation, and collapse) in magnetostrictive amorphous wires of the composition Fe/sub 77.5/Si/sub 7.5/B/sub 15/ were investigated. The wires were held under tensile stress (up to 1700 MPa in the case of as-quenched). The domain wall length and normal mobility (or damping) as functions of applied stress were found experimentally and from an ellipsoidal domain model. This allows the losses to be separated into eddy current and spin relaxation contributions. It was demonstrated that the spin relaxation contribution to the total damping parameter becomes dominant with increase of tension and leads to a dramatic decrease of the wall mobility. This is the reason cold-drawn and then tension-heated wires with high residual stress exhibit a much lower mobility in spite of the smaller diameter. The process of domain collapse at a collision of two domain walls is accompanied by a very sharp voltage pulse. It is shown that during the collapse the domain is affected by a growing internal magnetic field connected with an excess of domain surface energy in comparison with magnetostatic energy. >

The dynamic structure of a magnetic domain wall in a thin film with large uniaxial anisotropy perpendicular to the plane of the material has been determined by numerical integration of the Landau-Lifshitz-Gilbert equation. The geometry corresponds to a domain wall whose structure is uniform along the wall, but can vary normal to the wall and normal to the plane of the material. For external fields in the range of a few Oersted, a constant mobility is observed. In this region, the wall remains flat and horizontal Bloch lines (HBL) are not formed. At larger fields, HBLs are formed that propagate through the wall and punch through at the opposite surface from which they formed. During punch through, the region of the wall undergoing a quick 180 degrees rotation is seen to move backward compared with the rest of the wall. This causes the average wall position to be stationary during punch through. At larger fields, the structure of the domain wall is significantly more complex and multiple HBLs are found in the domain wall. >

The dynamics of magnetic domain‐wall motion in two dimensions for materials of interest to vertical Bloch‐line memory devices has been simulated on the Connection Machine. By use of a Fourier transform technique to evaluate the demagnetizing fields and explicit time integration of the Landau‐Lifshitz‐Gilbert equation, the equilibrium configuration of a domain wall and the dynamic structure of a wall in the presence of an external field has been studied. Horizontal Bloch‐line (HBL) nucleation, propagation and ‘‘punch through’’ can be observed in moving walls. The domain‐wall configuration for stripe chopping has been investigated and HBL motion is seen to be a dominant feature in this process.

The mechanism of the sensitive and stable large Barkhausen effects of as-cast amorphous magnetostrictive wires having three composition systems was investigated using measured values of stress-induced anisotropy constant saturation magnetostriction, residual internal stress, and MH hysteresis loop squareness M/sub r//M/sub s/. The entire composition range of FeCo is compared to FeCr with up to 10 at.% and FeNi with Ni up to 12 at.%. Matteucci effects were also investigated in magnetostrictive and nonmagnetostrictive amorphous wires magnetized with a longitudinal AC field, AC wire current, or AC field perpendicular to the wire axis. >

The effects of a cross-groove structure etched into the top surface of a 1.6-μm-thick bubble garnet film on an isolated stripe domain underneath one of the grooves is analyzed using a numerical model based on the Landau–Lifshitz–Gilbert equation. Warping of the edge of the domain wall underneath the cross groove has been observed. The cross groove generates an in-plane field parallel to the stripe domain wall, and reverses from one edge of the groove to the other. The field is not uniform across the width of the wall, but reverses with the magnetization across the wall. The net containment field generated has been found to be as high as 150 Oe, varying with the width of the stripe domain and the dimensions of the deeper groove.

Domain wall mobility in Permalloy films has been calculated as a function of thickness at 10, 80, and 160 nm which reflects the structure change of Neel, symmetric Bloch and C-shaped (asymmetric Bloch) domain walls. The mobility has been derived from the dynamics of a single nonperiodic domain wall using direct integration of the Landau–Lifshitz–Gilbert equation in a Cartesian lattice. This investigation allows for a detailed examination of spin precession, wall motion and overall magnetization distortion as the wall is moved in the presence of fields ranging from 0.5 to 5 Oe applied in the easy axis direction. At 10-nm-thick films, the mobility of a Neel wall is 30 m/s Oe. Wall motion takes place without noticeable distortion in the magnetization distribution in the vicinity of the Neel wall. For 80 nm-thick films, the mobility of a symmetric Bloch wall is 5 m/s Oe, or 20% less than the theoretical prediction for the mobility of a 180° domain wall model. At dynamic equilibrium, the symmetric Bloch wall h...

The three possible transitions of a wall involving a change of chirality and position of a vortex were previously identified in Permalloy™ using the Kerr effect. These transitions have now been simulated using direct integration of the Landau–Lifshitz–Gilbert equation in a 1 300 000 point Cartesian lattice. One transition is between two C-shaped, same chirality walls whose vortices are on opposite sides. The transition is done via a 32-nm-long pi-VBL structure at the surfaces and at the center via a shape transition 117 nm long. The pi-vertical Bloch line (pi-VBL), which changes chirality along the wall, conducts the flux between the walls of opposite chirality via a vortex structure by letting the magnetization rotate out of the plane of the walls at the center of this vortex. The Neel caps switch chirality via an antivortex flux at one surface and a vortex flux at the other surface. Another transition is a pi-VBL that takes place between two C-shaped, opposite chirality walls whose vortices are on oppos...

The Co‐Si‐B amorphous wires having the negative magnetostriction comprises shell and core domains and exhibits the re‐entrant flux reversal as the Fe‐Si‐B wire with positive magnetostriction. One of the characteristic features of Co based wires is that a sharp pulse voltage generation between two wire ends (Matteucci effect) is accompanied with re‐entrant flux reversal, which is useful for sensor application because of no need for sense windings. In this work, we studied the origin of the large Matteucci effect of Co‐Si‐B wires by domain observation with a Kerr microscope and by Sixtus–Tonks experiments by driving the reverse domain propagation with the circular fields generated by the current through wires. We also tried to measure the hysteresis loop in the circular direction by integrating the Matteucci voltage. It was found that the domain patterns of the Co‐Si‐B wire surface is not the previously reported bamboo configuration but the helical configuration. Most of the anisotropy of the amorphous materials is magnetostrictive in origin. The helical anisotropy of Co based wire seems consistent, if we assume the same residual stress distribution as in the steel rod quenched into the water. Because of the helical anisotropy, the Co wire has the big circular component of magnetization in the core domain as well as in the shell domain, and both domain can interact near the interface region. It was found that reverse domain propagation along the wire axis can be caused by application of the circular field and that the shell domain moves discontinuously during the re‐entrant flux reversal in the core domain. These circular magnetization components in both core and shell domains due to helical anisotropy and their interaction seems responsible for the large Matteucci effect in the Co‐Si‐B wires.

The authors measured the magnetic properties of Co-Si-B amorphous wire with negative magnetostriction, prepared by quenching in-rotating water, and results were compared with the properties of Fe wires with positive magnetostriction. The Co wire was found to exhibit large Barkhausen discontinuities as well as the Matteucci effect, as does Fe wire. It was also found that the Co wire has a bamboo-like domain pattern at the surface and has a reverse domain propagation mobility larger than the Fe wire.

Investigation for establishing a residual stress distribution and domain model for amorphous magnetostrictive alloy wires were carried out. Therefore, voltage pulse generation due to the large Barkhausen jump (e p ) and the Matteucci effect (e p ') was studied as a function of tensile and compressive stress applied in the axial direction. The wires had a composition of Fe 77.5 Si 7.5 B 15 , made by the in-water quenching technique. The amplitude of the voltage pulses (e p and e p ') and domain nucleation field (H*), are found to decrease smoothly to zero at a critical compressive stress of 5 kg/mm2for the as-cast wires. A reduction in the critical stress to 3 kg/mm2is observed after altering the wire diameter from 125 to 95 µm by etching. Tensile stress above 20 kg/mm2was found to increase e p and H*. Squareness ratio (B r /B s ) is observed to be a continous increasing function of applied stress in the range from compressive, zero to tensile stress, being about 0.5 at zero stress. By reducing the diameter by 50% through etching, B r /B s is found to increase by about 20%. The observed results is indicating a gradually varying residual stress such that the core has a stress induced axial anisotropy and the outer layers has an anisotropy perpendicular to the axis, caused by positive magnetostriction.

The mechanisms producing the sensitive large Barkhausen effect and the Matteucci effect in as-prepared amorphous magnetostrictive wires are investigated using colloid technique domain observations and Sixtus-Tonks domain propagation characteristics. Theoretical analysis of the pulse height of induced voltage at the pick-up windings and between both ends of the wire are made. This analysis is compared with experimental results. The Matteucci effect was remarkably improved by twisting or twisting then annealing the as-prepared wires. Jitter-less pulse generation is realized in the latter case.

New jitter-less pulse generator elements are presented using amorphous magnetostrictive wires. These elements induce sharp voltage pulses with ∼ 6V/cm2.Oe.turn due to the large Barkhausen jumps and with ∼ 6V/cm3.Oe due to the Matteucci effect using external ac fields of more than 0.1 Oe at frequencies between 0.01 Hz - 10 k Hz. Jitter of the pulse inducing phase is less than 1/10 and the pulse height is about twice that of Wiegand wires, respectively. The critical field of the large Barkhausen jump is controlled by heat treatment, etching, or twisting the wires. These wires are expected to be useful for high-performance pulse generator elements for high resolution rotary encorders by combining them with magnet ring, torque sensors, proximity sensors and magnetometers.

Amorphous magnetostrictive 50 μm diameter Fe 77.5 Si 7.5 B 15 wires exhibiting square and bistable hysteresis loops have been obtained by field-tension annealing and flash annealing treatments of cold-drawn as-quenched wires. Highest switching field, 1.3 Oe, and domain drive field, 0.5 Oe, for annealing temperature 330 C , time 30 min, axial tension 150 Kg/mm2and axial field 200 Oe are an order of magnitude improvement over the as-quenched (AQ) state. Corresponding induced peak voltage is 0.5 mV/turn with exciting sinusoidal field 2 Oe and 60 Hz. Shorter pulse generation elements (≈ 2 cm) than for AQ wires (≈ 6 cm) were realized with 0.5 mV/turn peak voltage. Maximum squareness ratio is close to unity, twice that of AQ (125 μm) wires.