Article last updated on: Sep 17, 2020

NTHU researchers manage to manipulate exchange bias by spin-orbit torque

Researchers from Taiwan's National Tsing Hua University (NTHU)managed to use a spin current to manipulate the exchange bias in Spin-Orbit Torque memory (SOT-MRAM). The researchers say that this has been a long-time challenge in the field.

MRAM chip Manipulating exchange bias by spin-orbit torque (NTHU)

To achieve this, the researchers added a platinum layer under the ferromagnetic and antiferromagnetic layers of the MRAM device. The researchers patented this technique before publishing their findings.

New material could finally enable fast, efficient and dense SOT-MRAM devices

SOT-MRAM (spin-orbit torque MRAM) has the potential to challenge STT-MRAM, as it is a faster, denser and much more efficient memory technology. Up until now, though, no suitable material that features both high electrical conductivity and a high spin hall effect was developed.

Now researchers at the Tokyo Institute of Technology have developed a new thin film material made from bismuth-antimony (BiSb) that is a topological insulator that simultaneously achieves a colossal spin Hall effect and high electrical conductivity - which means it could be used to create SOT-devices.

Imec researchers deposited SOT-MRAM devices on 300 mm wafers

Researchers from Imec fabricated spin-orbit torque MRAM (SOT-MRAM) devices on 300mm wafers using CMOS compatible processes. The researchers say that these devices offer unlimited endurance, fast switching speeds and low power consumption.

Imec says that SOT-MRAM can overcome the limitation of spin-transfer torque in MRAM memories, but up until now it was only demonstrated in a lab. The core of the SOT-MRAM is a magnetic tunnel junction in which a thin dielectric layer is sandwiched between a magnetic fixed layer and a magnetic free layer. SOT-MRAM devices feature switching of the free magnetic layer done by injecting an in-plane current in an adjacent SOT layer, unlike STT-MRAM where the current is injected perpendicularly into the magnetic tunnel junction and the read and write operation is performed through the same path.