MRAM – Magneto-resistive RAM. It and STT-RAM (Spin Transfer Torque RAM) are the same thing: non-volatile and byte-addressable memory using spin-polarised currents to change the magnetic orientation, and hence bit value, of a cell. Crocus, Everspin and STT are the main developers here and they claim their technology has DRAM speed and can replace DRAM and NAND, plus SRAM and NIR, and function as a universal memory. But no semiconductor foundry has adopted the chip design for mass production and consequently the technology is unproven as practical SCM.

STT-MRAM diagram.
Everspin MRAM.
Spin Memory MRAM chips.