Current State of STT-MRAM Cell-Based MTJ with MgO Tunnel Barrier

The current review focuses on magnetoresistive memory cells of the spin-transfer torque magnetic random access memory (STT-MRAM) type and the development of a physical model to describe their operation. STT-MRAM, a nonvolatile memory technology, uses spin-transfer torque (STT) to switch the magnetization of a free layer in a magnetic tunnel junction (MTJ), enabling data storage. The main objective of this work is to construct a physical model of the operation of an STT-MRAM cell, emphasizing the interaction between spin-polarized currents and the magnetization of the free layer of the magnetic tunnel junction. This study begins with a literature review of existing memory technologies, including volatile (e.g., dynamic random access memory (DRAM)) and nonvolatile (e.g., Flash or phase-change memory (PCM)), to identify the advantages of STT-MRAM. The analysis highlights the MTJ-based STT-MRAM system as a leading candidate for practical application due to its nonvolatile operation, high read/write speed, durability, and scalability. The key mechanism is the tunneling magnetoresistance (TMR) effect, in which the electrical resistance of an MTJ varies depending on the relative magnetization orientation of its ferromagnetic layers. The presented model shows that the performance of MTJ depends on the following critical parameters: electrical resistance, TMR coefficient, critical switching current, and thermal stability of the magnetization orientation of the “free” layer. The review concludes that optimizing these parameters requires certain trade-offs: for example, increasing thermal stability (by increasing magnetic anisotropy) can increase the critical switching current. Future work should focus on addressing material science and scaling challenges to meet industry needs for next-generation memory technologies.