Emerging memories
Why must the read current be limited in STT-MRAM?
- ABecause a large read current permanently changes the MTJ's resistance
- BBecause spin torque also acts during reads, so too large a current can accidentally reverse the storage layer's magnetization
- CBecause a large read current melts the magnetic layers
Show answer and explanation
Answer: B. Because spin torque also acts during reads, so too large a current can accidentally reverse the storage layer's magnetization
STT-MRAM writes by the spin torque of current passed through the MTJ. Reads pass current through the same path, so if the read current is close to the switching current, the magnetization may flip probabilistically on each read (read disturb). The read current is therefore designed to be much smaller than the write current.
- A. Permanent resistance degradation is not the main reason.
- B. Correct. Even a read current could cause an unintended write.
- C. Normal read currents do not melt the magnetic layers.