Nanometer-scale compass needles, known as skyrmions, are magnetic textures in certain materials. Their low-energy creation, manipulation and erasure make them ideal for future computing technologies, especially biomimetic computing.
Anjan Soumyanarayanan, a Research Scientist at A*STAR’s Institute of Materials Research and Engineering (IMRE), has been exploring the potential of skyrmions with lead author Xiaoye Chen; IMRE Lead Research Engineer, Hui Ru Tan; and other researchers at the Spin Technology for Electronic Devices (SpEED) team, as well as National University of Singapore.
Chen explained that conventional computers use transistor-based hardware to simulate neural networks for artificial intelligence tasks. Meanwhile, biomimetic computing uses specialised hardware that replicates the behaviour of biological brain cells.
"This allows a computer to natively perform neural network inference tasks without using an emulation layer, offering superior speed and efficiency compared to present-day computers," said Chen.
Despite their potential, skyrmions face stability hurdles. While they form compact structures under an external magnetic field, they become unstable and stretch into stripe-like formations when the field is removed, losing essential characteristics needed for computing applications.
To counter this, the team posited that integrating two distinct types of magnetic interactions within specially engineered magnetic layers can maintain skyrmion stability under ambient conditions without an externally applied magnetic field.
The team used wafer-scale techniques, transmission electron microscopy (TEM), and detailed simulations to tweak skyrmion behaviour in custom magnetic structures. They overcame hurdles by developing methods to quantify interlayer exchange coupling (IEC), a critical but not directly measurable parameter.
Ultrathin magnetic films are at the resolution limit of TEM imaging. “Distinguishing magnetic textures, like skyrmions, from structural defects is challenging. We developed custom imaging recipes and computational analysis techniques to address this,” Tan said.
Initial attempts to regulate skyrmions by altering the thickness of a single magnetic layer to manipulate IEC were unsuccessful due to the skyrmions' high sensitivity. This prompted the exploration of IEC with a second magnetic layer, a strategy not previously considered by the community. The team discovered that fine-tuning this layer provided much more precise control over skyrmion numbers.
"With two chiral layers coupled together by the second IEC, fluctuations in one chiral layer can be restored by the second layer," Chen explained. "This greatly improves the stability of skyrmions in chiral bilayers, which host the second IEC."
Controlling skyrmions without a magnetic field enables scalable, energy-efficient computing technologies. Meanwhile, extending IEC beyond traditional materials can create exotic 3D textures by coupling layers with different or complementary properties.
"Our work opens up the third dimension of magnetic films as a playground for materials exploration," said Soumyanarayanan, adding that this breakthrough enabled the creation of the world's first all-electrical skyrmionic magnetic tunnel junction—an advanced, high-efficiency memory device that reads and writes data using purely electrical signals.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE).