Browse Prior Art Database

Readout of Wall Coded Information in Bubble Memories With Resonance

IP.com Disclosure Number: IPCOM000053022D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Argyle, BE: AUTHOR [+3]

Abstract

It has recently been found that magnetic bubbles exhibit low frequency (0-30 MHz) resonances which are directly related to the domain wall state. We propose to read wall-coded information both in wall-coded permalloy memories and in bubble lattice memories by detecting these resonances.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Readout of Wall Coded Information in Bubble Memories With Resonance

It has recently been found that magnetic bubbles exhibit low frequency (0-30 MHz) resonances which are directly related to the domain wall state. We propose to read wall-coded information both in wall-coded permalloy memories and in bubble lattice memories by detecting these resonances.

Domain wall states are specified by the presence or absence of structural features called Bloch lines and Bloch points. Efforts have been made to use these wall states for information coding, using both the bubble lattice approach and more conventional permalloy memory approaches.

Ordinarily, wall-coded information is read by first transforming the wall state into a bubble/no bubble code using a gradient deflector and then subsequently using a conventional bubble detection technique, such as a stretcher/sensor. We propose to replace either the first or both of these device functions. For the case of a lattice file, readout of wall-coded information may be possible without ever disrupting the lattice. Heretofore, the lattice could not be read out without disrupting the lattice, which has led to serious complications and disadvantages.

Assume that the domain wall states called unichiral having winding number S=1 (no Bloch lines) and S=0 (two Bloch lines parallel to an applied external in- plane field H(p)) are used for information coding. Other choices may be made. Further, assume H(p) = 20 oersteds. Again, other choices are permissible. Then the S=0 bubble exhibits a sharp resonance at about 9 MHz in a bubble film of Gd,Ga:YIG [1], while the unichiral bubble does not. This is the physical basis. The following applications then seem feasible:

1. Replacement of the Gradient Deflector: A small loop or other structure capable of producing a localized 9 MHz RF magnetic field parallel to the film normal is placed at the exit of the major loop instead of the gradient deflector. A bubble suitably positioned with respect to this structure will be excited, provided its wall state is S=0. Then either one of the following effects may be used. At medium drive field on the order of 100 mOe, the resonating bubble will be displaced due to its agitation. This movement, which has been experimentally found to be a random hopping, may be directed by some suitable guiding structure which prohibits displacement in all but one desired direction which subsequently transfers the bubble into an annihilator. If the S=0 bubble is replaced by a S=1/2 bubble in the coding scheme, the guiding structure would not be necessary. Exciting a S=1/2 bubble at its resonance frequency of 12 MHz produces continuous m...