The Magnetic Memory cell is built from on Magnetic Tunneling Junction (MTJ) cells.
- Free ferromagnetic layer: easy to change magnetic polarity
- Pinned ferromagnetic layer: hard to change magnetic polarity
- Pinning anitferromgnetic layer: works on pinned layer to make it magnetically "hard"
- Stack acts as a resistor: current tunnels top to bottom through insulating layer
When Free and Pinned layers have same orientation, resistance is lower: R=10Kohms
A small electrical field from a nearby current forces Free layer to switch magnetic polarity. Then R increases to 15Kohms.
A pair of MTJ cells in a differential circuit can store state as '1' or '0'.