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Paced Automotion of Magnetic Bubble Domains

IP.com Disclosure Number: IPCOM000089407D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Slonczewski, JC: AUTHOR

Abstract

Automotion of magnetic bubble domains has been described by Argyle et al in the AIP Conference Proceedings (joint MMM-Intermag Conference, Pittsburgh, Pa.) No. 34, p. 131 (1976), and also in the 1977 Digest of the Intermag Conference, Los Angeles, California, paper 16-4. In this technique, time varying magnetic fields having no spatial gradients are applied to bubble domains. This causes precession of magnetization vectors in the wall of the domain which moves them in the absence of propagation structure. The automotion velocity is a continuous function of certain current amplitudes and bubble material parameters which may fluctuate spatially or temporally.

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Paced Automotion of Magnetic Bubble Domains

Automotion of magnetic bubble domains has been described by Argyle et al in the AIP Conference Proceedings (joint MMM-Intermag Conference, Pittsburgh, Pa.) No. 34, p. 131 (1976), and also in the 1977 Digest of the Intermag Conference, Los Angeles, California, paper 16-4. In this technique, time varying magnetic fields having no spatial gradients are applied to bubble domains. This causes precession of magnetization vectors in the wall of the domain which moves them in the absence of propagation structure. The automotion velocity is a continuous function of certain current amplitudes and bubble material parameters which may fluctuate spatially or temporally. In a device using automotion, such as a bubble lattice device, it is necessary to keep the automoted bubble domains in tempo with an external clock in spite of fluctuations in the material properties, drive amplitudes, etc.

Automotion of bubble domains in a lattice can be paced by combining (1) a spatial variation of bubble material property whose period is some multiple of the lattice period and (2) modulation, at the clock frequency, of at least one of the two or three drive-field amplitudes used to produce automotion. In particular, thickness variations, annealing, or magnetic ink deposits can be used to pace the automotion.

The instantaneous lattice velocity is written dx/dt = -F(x) sin kx + F(0) + F(1) sin Omega t (1) where, in the simple case, 2 Pi/k is the period of the lattice, Omega/2Pi is the clock frequency, and F(x)(>0), F(0), and F(1)()0) are force amplitudes converted into velocity units through domain mobility. F(0) and F(1) are amplitudes of automotion force. F(x) measures the effect of spatial inhomogeneity. In existing garnets automotion velocities ranging up to 200 cm/sec. have been observed. It is understood that F(1) sin Omega t represents the envelope of the higher frequency (>10 Omega/2 Pi) field oscillation required for the automotion effect itself, or else it represents the modulation of the DC in- plane field occurring in some forms of automotion. For maximum efficiency F(0) + F(1) will be equal to the maximum automotion velocity the system is capable of attaining. Let us approximate the solution with the expression x = (Omega/k)t + c + A sin Omega t + B cos Omega t (2) where Omega/k is the mean lattice velocity and c is a constant displacement of the lattice from the static equilibrium position dictated by the spatial forces. The problem is to determine conditions under which constants c, A, and B can be found. Equation (2) is substituted into equation (1), sin kx is Taylor-expanded to first order in A and B and the coefficients of 1, sin Omega t, and cos Omega t are equated. Eliminating A and B from the resulting three equations, the following relation is obtained. -kF(1)F(x) over 2 Omega cos k c = F(0) - Omega over k - kF/2/(x) over 2 Omega (3). Since Absolute cos k c Absolute </=1, a solution for c can on...