Magnetic Random&;#x02010;Access Memory

This chapter reviews the technology of magnetic random-access memory (MRAM) developed since 1996, with a particular focus on spin-transfer torque MRAM (STT-MRAM) and thermally assisted MRAM (TA-MRAM), which are currently receiving the most attention. After an introduction, Section 5.2 discusses the storage function in MRAM and how to design the storage layer in magnetic tunnel junctions (MTJ) to achieve the required memory retention. Section 5.3 is devoted to the read function and conditions for reading without altering the written information. The following sections are devoted to the various technologies of MTJ-based MRAM: MRAM written by magnetic field pulses (Section 5.4), STT-MRAM (Section 5.5), TA-MRAM (Section 5.6), and three-terminal MRAM (Section 5.7). Section 5.8 compares the MRAM technologies, particularly the STT-MRAMs, with other nonvolatile memory technologies, particularly redox-RAM.