Spin-Transfer Torque RAM (STT-RAM)

Spin-Transfer Torque RAM (STT-RAM) has emerged as a potential candidate for Universal memory.

Spin-transfer torque magnetic random-access memory (STT-RAM or STT-MRAM) use magnetic tunnel junction (MTJ) to store the data. An MTJ consists of two ferromagnetic layers and one tunnel barrier layer. The two ferromagnetic layers are called the reference layer and the free layer. The magnetic direction of the reference layer remains

fixed, while the magnetic direction of the free layer can be parallel or anti-parallel, which is used to represent the binary data stored in the cell.

In the CMU evaluation, there are several advantage to use STT-RAM:

  1. An STT-RAM main memory can achieve performance comparable to DRAM main memory, and
  2. An STT-RAM main memory can bring 60% reduction in average memory subsystem energy over DRAM main memory.