Emerging memories

Which correctly describes the tunnel magnetoresistance (TMR) ratio of an MTJ?

  1. AThe difference between the antiparallel and parallel resistances divided by the parallel resistance
  2. BThe ratio of insulator thickness to magnetic layer thickness
  3. CThe maximum current that can flow through the MTJ
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Answer: A. The difference between the antiparallel and parallel resistances divided by the parallel resistance

The TMR ratio is (R_antiparallel − R_parallel) / R_parallel and indicates how different the two states' resistances are. The larger the TMR ratio, the easier it is to distinguish 0 from 1. With an MgO tunnel barrier, TMR ratios exceeding 100% are obtained at room temperature.

  • A. Correct. It is the ratio of the resistance difference between the two states.
  • B. It is not a ratio of film thicknesses.
  • C. The maximum current is a separate property from the TMR ratio.
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More Emerging memories questions

  1. In an MTJ, how do the resistances compare when the magnetizations of the two magnetic layers are parallel versus antiparallel?
  2. Which correctly describes the roles of the two magnetic layers in an MTJ?
  3. In phase-change memory (PCM), how is a cell heated to put it into the low-resistance crystalline state (set)?
  4. On the hysteresis loop (polarization versus electric field) of a ferroelectric, what is the polarization that remains when the field returns to zero called?
  5. Which external environmental factor requires care when using MRAM?