Browse Prior Art Database

Bloch Line Information Writer for Magnetic Bubble Store

IP.com Disclosure Number: IPCOM000083989D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Slonczewski, JC: AUTHOR

Abstract

Bubble domain lattice storage has been proposed based on Bloch-line (BL) coding. The bubbles become encoded with BLs during the process of bubble nucleation or creation. The net winding number I, corresponding to the information state in any given bubble remains constant throughout the life of the bubble.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Bloch Line Information Writer for Magnetic Bubble Store

Bubble domain lattice storage has been proposed based on Bloch-line (BL) coding. The bubbles become encoded with BLs during the process of bubble nucleation or creation. The net winding number I, corresponding to the information state in any given bubble remains constant throughout the life of the bubble.

This device controllably alters I of a given bubble without annihilating it or creating a new bubble. Thus, it eliminates the need for bins or reservoirs of already coded bubbles.

To illustrate, I=0 and I=1 are to be the information states. Fig. 1 shows six successive bubble stations within the writer. As indicated, a track is provided to guide the bubble from one station to the next. The track may be etched, or provided by magnetic strips, or effectively provided by T and I bars or equivalent rotating-field propagators, not shown. The bubble is propelled along the track by a moderate field gradient generated by current strips, not shown, or by a conventional rotating-field overlay pattern, not shown. In addition, a static, inplane bias field H(IP) approx. 4 Pi M(s) is applied parallel to y throughout the writer. The writer operates as follows.

A bubble with arbitrary state enters station 1. The combined action of its motion and H(IP) causes whatever +/- 360 degrees Bloch lines happen to be present to gather along the +/- y axis, respectively.

At station 2, magnetic overlay 1 is saturated by H(IP) so that no domain walls are present in it. This requires H(IP) > 4 Pi M(1)W(1) d/-1/, where M(1) is the spontaneous magnetization, W(1) is the thickness of the magnetic layer, and d is the bubble diameter or other minimum dimension. The overlay may be a NiFe or ion-implanted layer with easy direction in the plane. Being in exchange contact with the bubble material, the overlay supplies Bloch points which enable all of the Bloch lines to annihilate themselves. The information state is now I=0.

Station 3 includes a conducting loop oriented such that a field may be impressed substantially on only the right half of the bubble. if the state I=0 is desired, no current flows in this loop and the bubble emerges from station 3 in the state I=0. If the state I=1 is desired, a pulsed current J is impressed by an external control. The shape of the pulse is such that the resulting H(z)(t) normal to the plane satisfies the condition: Gamma Integral H(z)(t) dt = 2Pi, where Gamma(approx. 10/7/ oe/-1/ sec/-1/) is the gyromagnetic ratio.

In addition, the amplitude of H(z) must be more than 1 oersted for a medium- loss garnet to drive the wall velocity into the nonlinear region. It...