Utilizes soft magnetic materials and magnetic domains.
Comparable to magnetic disk memories used in computers.
Bubbles moved electrically at high speed for data storage and retrieval.
Examples of Magnetic Bubble Materials
Key Material Examples:
Rare earth ortho-ferrites
Hexagonal ferrites
Rare earth ferromagnetic garnets
Amorphous bubble materials
Magnetic Domain Structures
Magnetic Films:
Made of ferrites or garnets.
Domains appear as wavy strips (movable and electrically moved).
Strips are arranged in two orientations: pointing up or down.
When polarized light is applied, strips appear as bright or dark.
Behavior Under Magnetic Field
Effect of Magnetic Field:
Varying perpendicular magnetic fields affect strip behavior.
As the field increases, strips shrink and form bubbles.
Bubbles are small circular areas concentrated into few micrometers.
Stable in specific applied regions.
Conversion Process
Conversion Graph:
X-axis: Shape of magnetic strips.
Y-axis: Applied magnetic field.
Increasing magnetic field causes strip shape to decrease, forming bubbles.
Complete magnetization leads to maximum bubble collapse.
Structure of Magnetic Bubble Memory
Construction:
Thin magnetic garnet layer grown epitaxially on non-magnetic substrate.
Magnetic strips subjected to maximum perpendicular field: some strips bright, others dark.
Permanent magnets and conductors used to produce and rotate magnetic bubbles.
Advantages of Magnetic Bubble Memory
Non-Volatile:
High density due to small bubble size.
Storage capacity of 10 million bits per cm².
Reduced readout and storage time compared to other forms.
Limitations
Readout Speed:
Not a random access memory.
Data must be read serially, limiting speed to a few hundred kilobytes per second.
Applications
Usage Areas:
Micro-pusher chips, SD cards, memory chips.
Utilized in FRAM and other chip technologies.
Magnetic bubble memory combines unique magnetic domain structures, high-speed operation, and high data density, despite certain limitations in data access speed.