In an MTJ, the difference between the resistances in the parallel and antiparallel states divided by the parallel-state resistance. The larger it is, the easier it is to tell 0 from 1; MgO barriers give large values.
Field: Emerging memories
Even with a TMR ratio of 100–200%, the resistances differ by only 2–3×, giving smaller read margins than DRAM or flash.
How is data read from MRAM?The TMR ratio is (R_antiparallel − R_parallel)/R_parallel, expressing how different the two resistance states are; with R_parallel = 2 kΩ and R_antiparallel = 5 kΩ it is 150%.
Which correctly describes the tunnel magnetoresistance (TMR…MRAM Magnetic tunnel junction (MTJ) 3D XPoint Chalcogenide Cross-point memory Electroforming FeFET (ferroelectric FET) FeRAM (ferroelectric RAM) In-memory computing PCM (phase-change memory)