Microcomputer Circuits and Processes

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Figure 4.6
(a) Same as in figure 4.5, but with bias field increased. Domains aligned opposite to the
bias field direction begin to shrink.
(b) Bias field increased enough to shrink oppositely aligned domains into small magnetic
bubbles.
another, the bubbles will move to the place of greater field strength, in
the same way as iron filings are attracted to the end of a bar magnet.
In a bubble memory, a bubble or absence of a bubble represent a
logical 1 or a 0 respectively, and these bits are made to hop around in a
cyclic fashion from one memory cell to another. Since the bits are
magnetic, the memory cellsmust be made ofmagnetic material. Figure 4.7
shows two cells out of a long line of cells. The progress of one bubble
from the first cell to the second is also shown.
2 3
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5
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6 7 8
Figure 4.7
The history of a bubble and two memory cells, or 'chevrons'. As the field is slowly
rotated, the bubble follows, then jumps across the cell gap. The arrows show directions
of the magnetic field as it rotates.
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