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The average value of the perpendicular component of the demagnetizing field in case of elliptical cylindrical domains is evaluated. The value of the field is a function of the size and eccentricity of the in-plane domain geometry. The field assumes different values for different locations. The extreme values of the field at the extreme locations of the boundary wall of the cylindrical domains are calculated.

Domain-wall motion in pure and doped yttrium-iron-garnet single crystals with composition Y3Fe5−δSiδO12, 0<δ<0.12, has been investigated over the temperature range 4.2°−300°K. Samples were prepared in a picture-frame geometry to carry a single movable wall. Wall mobility for our pure sample showed a temperature dependence similar to that reported by Hagedorn and Gyorgy; however, our values for wall mobility are 4–7 factors lower than theirs, probably reflecting the simpler domain structure of our samples. As expected, the wall inverse mobility increases linearly with the increase in silicon concentration (or equivalently, with Fe2+ ion concentration). However, as a function of temperature the inverse mobility of silicon-doped samples, unexpectedly, shows a peak at about 20°K. The over-all temperature dependence does not agree with the diffusion after-effect model which is based on the assumption that wall damping is the result of 3d-electron transitions between Fe2+ and Fe3+ cations in the octahedral sublattice. The behavior, however, is very similar to that found for the temperature dependence of the microwave-resonance linewidth of silicon-doped samples. In both cases, because of the short time of spin reorientation relative to the electron-diffusion relaxation time, it is more likely that the loss mechanism is dominated by a localized relaxation process occurring between the energy levels of Fe2+ ions.

r' / r 0< 1 the angle y subtended by the tangent to the domain. boundary and the radius r is very close to 90'. The angle (3 = 90 --y lying between the tangent to the wall and the normal to r is very small, such that cos.8=I, and sin.8=.8=(I/r) (dr/dO). The angle which appears in Eqs. (II) and (16) is related to the angles 0 and .8 by the relation O=a+.8.

The anisotropy term in the specific wall energy and the gradient in the driving field force cylindrical domains to deviate from circular geometry. When the deviation is large, its treatment as a perturbation term is not valid. An elliptical boundary for the domain is suggested, and calculations are made for the effect of the eccentricity of the elliptical boundary upon the domain damping constant β, and the coercive force Fc. It is found that β and Fc decrease nonlinearly as functions of the increasing eccentricity if the domain is allowed to move along the ellipse major-axis direction. If the motion is along the ellipse minor-axis direction, β and Fc increase as the eccentricity is increased. The effective mass of the domain is found to be dependent upon the magnitude of the eccentricity.

A method for calculating the perpendicular field of the Permalloy propagating overlay of bubble devices is presented. The Permalloy overlay is thought of as being built of a collection of basic building blocks. The field due to a convenient basic building block is obtained in a closed form. The resultant field due to the collection of the basic blocks which constitutes the overlay pattern is obtained by summing up the fields due to the individual basic blocks with their respective position and orientation.

This paper describes the particulars of a garnet single cryst a l growth program. Crystals are grown from a lead oxide, lea d flouride and lioric oxide flux. A temperature cycling technique and a temper a ture gradient across a sealed crucible eliminate the crc 1tion of ar excessive number of nucleation centers and result in larger crystals. Some growth mechanisms are revealed from observations of crystals at different growth stages . The crystals show both latteral and vertical growth modes. The growth is s imilar to a prolonged liquid phase epitaxial growth. Build-up of inclusions and strain is discussed,and the results of crystal etching are present ed.

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