Smaller, Faster, More Stable Magnetic Memory (MRAM) with Negligible Energy Footprint Revolutionizes Portable Memories

Does your portable wireless design need the speed of SRAM, the high density of DRAM and the non-volatility of Flash in a single low-power memory? If so, it’s time to look into Magnetic Random Access Memories (MRAM).  Today’s portable electronics (i.e. smart phones, tablets, etc.) have become computationally intensive devices as the user interface has migrated to a fully multimedia experience. To provide the performance required for these applications, the portable electronics designer uses multiple types of memories: (1) a medium-speed random access memory for continuously changing data, (2) a high-speed memory for caching instructions to the CPU, and (3) a slower, nonvolatile memory for long-term information storage when the power is removed. Combining all of these memory types into a single memory has been a long-standing goal of the semiconductor industry.

IMPACT/BENEFITS OF RESEARCH OR PROJECT

The focus of this effort has been to demonstrate a working memory element, with ultrahigh performance in terms of energy (10x more energy-efficient than state of the art, with a roadmap to further improve to 1000x more efficient with a combination of materials and mechanical effects) and ultrafast access speeds (write times better than 1 ns). To do this the TANMS team designed, fabricated, and tested voltage-controlled magnetoelectric tunnel junctions (MTJs), where the writing of information (i.e. switching of the magnetic free layer) is performed by sub-nanosecond pulses of voltage applied to the device. The applied voltage exerts a torque on the magnetization via the voltage-controlled magnetic anisotropy (VCMA) effect, i.e. charge interaction. The VCMA effect modifies the occupancy of different atomic orbitals when a voltage is applied, which, due to spin-orbit coupling, results in a change of magnetic anisotropy.

The single memory bit designed, fabricated, and tested in TANMS includes a readout mechanism using the tunneling magnetoresistance (TMR) effect. This combined writing/reading approach provides a fully functional memory cell with ultralow-power, electrical read/write mechanisms, as well as nonvolatile storage of information once the voltage is removed. Therefore, TANMS has demonstrated a fully operational single memory bit of information during the second year of study.