Researchers at UCLA's Henry Samueli School of Engineering and Applied Science have made a discovery that can dramatically lower the power consumption and increase the bit density of magnetoresistive random access memory, otherwise known as MRAM. In existing MRAM implementations, a process called spin-transfer torque is used to write to the memory. This technique relies on an electrical current to move the electrons responsible for representing data. The current generates heat, and it limits how densly bits can be packed.
Instead of using an electrical current, the UCLA researchers have been able to flip MRAM bits using voltage. They've dubbed their creation MeRAM, or magnetoelectric random access memory. The press release explains how it works:
MeRAM uses nanoscale structures called voltage-controlled magnet-insulator junctions, which have several layers stacked on top of each other, including two composed of magnetic materials. However, while one layer's magnetic direction is fixed, the other can be manipulated via an electric field. The devices are specially designed to be sensitive to electric fields. When the electric field is applied, it results in voltage — a difference in electric potential between the two magnetic layers. This voltage accumulates or depletes the electrons at the surface of these layers, writing bits of information into the memory.
MeRAM is reportedly 10-1000 times more energy efficient than traditonal MRAM, and it's supposed to have five times the bit density. Because MeRAM is non-volatile, it could potentially replace the flash memory used in solid-state drives, tablets, and smartphones. Best of all, there are no endurance limitations attached.
Magnetic-based memory isn't just confined to research labs. Everspin is current sampling (PDF) a 64Mb MRAM device that promises bandwith of 3.2GB/s in a 16-chip configuration—that's DRAM-like performance. Much higher densities will be needed before MRAM becomes a viable replacement for flash in consumer-grade devices, but MeRAM might get us there sooner.
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