Magnetoresistive random access memory (MRAM) is the forerunning
candidate for the next generation digital technology. However,
manipulating MRAM efficiently and effectively has been challenging. A
revolutionary breakthrough was recently achieved by an interdisciplinary
research team based at National Tsing Hua University (NTHU) in Taiwan,
led by Prof. Chih-Huang Lai and Prof. Hsiu-Hau Lin. By adding a layer of
platinum, only a few nanometers thick, it generates spin current
to switch the pinned magnetic moments at will – a task that has never
been accomplished before.
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Professor Lai Chih-huang (left) and Lin Hsiu-hau of NTHU using hand gestures to represent the 0-1 concept in digital memory. (Photo: National Tsing Hua University)
From mobile phones to computers, wearable devices, the Internet of
Things, and smart city operations, data processing and storage are
essential. To allow faster reading and writing, less power consumption
and retaining data through a power outage, MRAM stands out in the keen
competitions. Lai and Lin’s breakthrough, published in Nature
Materials recently, adds wings to MRAM technology and attracts
attentions from both industry and academy.
Steering spin currents in MRAM
At present, information processing in digital devices is mainly carried
out using dynamic random access memory (DRAM), but it consumes
significant power and faces serious hurdles when reduced in size.
DRAM utilizes the charges of electrons. “But, electrons have both charge
and spin.” Lai said, “Why can’t one work with electron spins to
manipulate MRAM?” To put the idea into practice, Lai and Lin formed an
interdisciplinary research team with doctoral students Bohong Lin and
Lin explained that the structure of MRAM is like a sandwich. The upper
layer consists of a freely flipping magnet, in charge of data
computation, while the bottom layer consists of a fixed magnet,
responsible for data storage; and these two layers are separated by an
The challenge is to switch these layers of different natures by
electrical means. After a long series of experiments, they found the key
ingredient: a nanometer layer of platinum. Due to spin-orbit
interactions, the electric current drives the collective motion of
electron spins first. The spin current then switches the pinned magnetic
moment effectively and precisely.
Spintronics blazing hot
In recent years, NTHU has been promoting cross-disciplinary cooperation,
such as the MRAM research conducted by the physicist Lin and the
materials expert Lai, who have learned to work together seamlessly.
Major international companies all participate in the competition of MRAM
development, including Samsung, Intel, and TSMC. It’s likely that mass
production of high-density MRAM will begin sometime this year, a
development where the research team led by Lai and Lin has played a key
The research team is currently extending their groundbreaking discovery
to other structures, and their ongoing findings are expected to have
major impacts on the development of memory industry. In Lai’s view, the
development of MRAM technology is going to have a decisive influence on
the future competitiveness of Taiwan’s semiconductor industry.