In his 2005 paper, Professor of Physics Johan Åkerman touted magnetoresistive random access memory (MRAM) as a promising candidate for a "universal memory" that could replace the various types of memory commonly found alongside each other in modern electronic devices. A team of researchers from the National University of Singapore (NUS) and Saudi Arabia's King Abdullah University of Science and Technology (KAUST) has now developed a new type of MRAM that could see Åkerman's vision become a reality.
Currently, many devices pack static random access memory (SRAM), dynamic random access memory (DRAM), and Flash memory, with each offering their own particular advantages. SRAM is fast but volatile, meaning the data it stores is lost when the power is switched off. DRAM offers greater memory densities than SRAM and is cheaper, but is also volatile and needs to be refreshed periodically to retain information, making it more power hungry. Finally, Flash memory is non-volatile, meaning it retains data even when the power is switched off, but is still relatively expensive.
MRAM technology offers the potential of providing all the advantages of these three types of memory, with none of the disadvantages. It promises greater storage density, reduced power consumption, and would retain data without power. Although it has been under development since the 1990s, continuing improvements in Flash and DRAM have kept MRAM largely on the sidelines.
Current MRAM technology stores data using magnetic storage elements formed by two ferromagnetic plates separated by a thin insulating layer. However, the reliability of MRAM suffers because these plates, which have a thickness of less than one nanometer, are difficult to manufacture reliably, resulting in memory that is generally only able to retain data for less than a year.
The research team has been able to replace the ferromagnetic plates with an alternative film structure incorporating magnetic multilayer structures as thick as 20 nanometers. The researchers say this technique allows data to be retained for a minimum of 20 years, making their next-gen MRAM chip attractive for a wide range of applications.
"From the consumer’s standpoint, we will no longer need to wait for our computers or laptops to boot up," says Dr Yang Hyunsoo, who led the research team. "Storage space will increase, and memory will be so enhanced that there is no need to regularly hit the 'save' button as fresh data will stay intact even in the case of a power failure. Devices and equipment can now have bigger memory with no loss for at least 20 years or probably more."
"With the heavy reliance on our mobile phones these days, we usually need to charge them daily," adds Dr Yang. "Using our new technology, we may only need to charge them on a weekly basis."
The researchers believe their breakthrough will change the architecture of computers, making them cheaper to manufacture. The team says it has already received strong interest from the semiconductor industry in its new technique, for which it has already filed a US provisional patent. The researchers now plan to apply the new structure in memory cells and are looking for industry partners to help develop a "spin-orbit torque-based MRAM."
The new structure is detailed in a paper published online in Physical Review Letters.