摘要:

Dependence of bubble state stability and translational apparent bubble velocity on the direction of an in‐plane field has been observed in Permalloy‐coated garnet films. Bubble state stability and velocity are affected by the position of planar domains with respect to the direction of bubble motion. The position of the planar domain is determined by the direction of in‐plane field. When the planar domains trail the bubbles, the bubbles move faster and the stable regions for bubble‐wall states are larger than when the planar domains lead the bubbles. The difference in stable regions is caused by an increased mutual interaction between the bubble and the planar domain when the planar domain leads the bubble.

ISSN:0021-8979    

DOI:10.1063/1.326787

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We propose principles for interpreting magnetic‐bubble dynamics in a rotating‐gradient experiment when no external in‐plane field is present. If the orbit of the bubble is circular, simultaneous determinations of radius and phase lag with respect to the drive may be interpreted to measure the mobility coefficient and the velocity‐momentum [V=V(P)] relation. Investigation of the stability of the circular orbit shows that in one limiting case the segments ofV(P) having a positive slope will be accessible to experiment. We illustrate dependences ofVonPexpected for static bubbles with 1) small numbers of vertical Bloch lines, 2) horizontal Bloch lines, and 3) large numbers of vertical Bloch lines. We conclude that rotating‐gradient measurements can determine the Bloch‐line structure of the circulating bubble. The basically new element present in such experiments is the transverse component of effective bubble mass, which differs from the longitudinal component and will be much greater than the Do¨ring mass whenever Bloch lines are present.

ISSN:0021-8979    

DOI:10.1063/1.326788

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Transport methods using high speed photography and ferromagnetic resonance are compared for the determination of the dynamic characteristics of bubble materials. The mobility and the saturation velocity are calculated with the use of parallel and perpendicular magnetic resonance fields and linewidth. Experiments are performed with 2‐&mgr;m bubbles Ga, Al or (Ca, Ge) substituted (Eu, Lu)3Fe5O12and (Y Sm Lu Ca)3(Fe Ge)5O12garnet films. In films experimented with, the mobilities range between 400 and 1000 cm/S Oe and the saturation velocities between 800 and 2000 cm/s. A good agreement has been found between both methods.

ISSN:0021-8979    

DOI:10.1063/1.326789

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Stripe head propagation has been investigated in ion‐implanted garnet films using high speed photography with 10 nsec laser pulse illumination. For a given in‐plane field applied along the stripe, the stripe head velocity increases linearly with drive until a peak drive is reached, beyond which the velocity drops. The peak velocity increases with in‐plane field magnitude and depends on which of the two directions parallel to the stripe that the in‐plane field is applied. Numerical calculations of the dynamic wall structure are made to predict the peak velocity as a function of in‐plane field magnitude and direction. The effect of the implanted layer is taken into account by using a surface pinning condition. Results show that velocity breakdown occurs when a horizontal Bloch line (HBL) is nucleated. The velocity asymmetry with respect to in‐plane field direction occurs because the HBL nucleates at opposite surfaces for the two in‐plane field directions. The implanted layer inhibits HBL nucleation by pinning the surface spins, thus producing a higher peak velocity.

ISSN:0021-8979    

DOI:10.1063/1.326790

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The dynamic behavior of an isolated straight stripe domain is reported in garnet films with relatively low damping. In the low drive field region, the translation velocity increases linearly with drive field, then it breaks down over a peak velocity followed by repeated increase and decrease of the velocity with increasing drive field. The peak velocity and the critical field for velocity breakdown are increased by a static in‐plane field applied parallel to the walls of stripe domain, while they are scarcely influenced by an in‐plane field applied perpendicular to them. In case of ion‐implanted film, the peak velocity as well as the critical field depend on the direction of the magnetization within the walls. These experimental results are interpreted quantitatively by a model in which the nucleation, the propagation and the punch‐through of the horizontal Bloch lines are considered.

ISSN:0021-8979    

DOI:10.1063/1.326791

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Localized stress fields which are present at the edges of evaporated layers pin domain walls. In the experiments Cr layers on epitaxial EuGaYIG films were primarily used to study these effects. Since the domain walls are pinned at the layer edges, magnetic bubbles can be pinned with their centers either inside or outside the layer. To pull off the bubbles a pulsed field gradient established by parallel conductor lines was applied. In total, five different interaction forces can be distinguished. The pinning forces are proportional to the stress in the film, i.e. the layer thickness, and independent of the layer width as long as the width exceeds the bubble diameter. For edges with a normal parallel to ⟨110⟩ the pinning is symmetric for both edges whereas for ⟨211⟩ there is an asymmetry. Most of these effects agree qualitatively with theoretical predictions by Dishman et al., which are based on perturbations of the domain wall energy through inverse magnetostriction.

ISSN:0021-8979    

DOI:10.1063/1.326792

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Magnetization distribution in two‐dimensional walls of cylindrically symmetric bubbles is calculated numerically. Fundamental static properties, such as the total energy, the radius, the wall width and the collapse instability condition for such bubbles are obtained and discussed. Some dynamic properties like the velocity versus momentum relationships for considered bubbles are also calculated. The results may be used for explanation of various experimental effects.

ISSN:0021-8979    

DOI:10.1063/1.326793

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The micromagnetic model previously reported has been applied to a selection of materials and to an additional wall type. The stability of unichiral (S=1) walls and walls containing a single horizontal Bloch line pair (HBLP) has been studied numerically for Q in the range 1.4 to 4.6, and for material lengths, normalized to film thickness, between 0.05775 and 0.462. Wall structure, in the form of contour maps and profiles of azimuthal angle, have been obtained for walls without and with a 2&pgr; twist (HBLP) centered on the film midplane. The dependence of structural quantities on material parameters is also presented. Bubble mobility dependence on quasi‐static wall structure was investigated from the point of view of the gyrovector force density concept. The dependence of the peak magnitude of the gyrovector on material length is discussed, and a relief map of the gyrovector magnitude for a wall containing an HBLP is presented.

ISSN:0021-8979    

DOI:10.1063/1.326794

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Domain motion and stretching in chevron expander stacks is characterized over the frequency range 100 kHz to 500 kHz. Lateral motion through the stacks shows stable resting positions at the two ends and at the centre of the chevrons with the strip transferring quickly between these. The transfer requires a progressively longer phase angle as the frequency is increased and this reduces the resting phases, e.g. the resting phase at the apex is 45° at 100 kHz, but only 10° at 500 kHz. Transverse expansion takes place principally during the pauses at the ends of the chevrons. The form of the stretching is largely linear with phase, but slows to a limiting value before a lateral transition occurs. The speed of expansion at different frequencies is fairly constant at about 40 m/sec. in the linear region at 40 Oe drive and mid‐bias. However, the linear region reduces in phase‐width at increased frequencies to allow only minimal expansion, combined with a small contraction when crossing the gap between stacks, at frequencies above 400 kHz in these specimens. At low bias the degree of expansion tends to a limit, corresponding to a maximum domain‐tip speed of approximately 52 m/sec. The stretching of the two ends of the strip is not truly symmetrical. At low bias the expansion in the direction of the chevron apexes is slightly greater, and at high bias the situation is reversed. These differences are related to different phase and velocity variations with bias in the two directions.

ISSN:0021-8979    

DOI:10.1063/1.326795

出版商:AIP    

年代:1979

数据来源: AIP