Antiferromagnets may accelerate spintronics

A team of physicists from the Hefei Institutes of Physical Science (HFIPS) at the Chinese Academy of Sciences (CAS) has made a significant discovery related to antiferromagnets, which could revolutionize spintronics, a cutting-edge technology for data storage and processing that aims to overcome the limitations of traditional electronics.

The researchers’ findings were published in the prestigious journal Physical Review Letters.

Spintronics is an emerging field that utilizes the spin of electrons within magnetic materials to encode and process information. In spintronics, spin-polarized electric currents play a crucial role because they enable the manipulation and detection of magnetic moment directions, which correspond to binary states of 1s and 0s. Currently, most spintronic devices rely on ferromagnets, which have a net magnetization that efficiently spin polarizes electric currents.

Antiferromagnets, on the other hand, have opposite magnetic moments that align alternately and have been less explored in spintronics. However, they hold the potential for even faster and smaller spintronic devices. A common belief has been that antiferromagnets, which possess zero net magnetization, only support spin-neutral currents that are considered useless for spintronics. This is because antiferromagnets consist of two antiparallel aligned magnetic sublattices, and their properties were thought to be “averaged out” over these sublattices, resulting in a lack of spin dependence.

However, Professor Shao Ding-Fu, who led the research team, had a different perspective. He envisioned that collinear antiferromagnets could function as “electrical circuits” with the two magnetic sublattices connected in parallel. With this intuitive picture in mind, Prof. Shao and his collaborators theorized that magnetic sublattices could locally polarize electric currents, leading to hidden staggered spin currents within the overall spin-neutral current.

These staggered spin currents were named “Néel spin currents” by Professor Shao, in honor of Louis Néel, a Nobel laureate who made significant contributions to the understanding of antiferromagnetism.

The discovery of Néel spin currents represents a unique characteristic of antiferromagnets that had not been previously recognized. These currents have the potential to generate spin-dependent properties that were traditionally considered incompatible with antiferromagnets, such as spin-transfer torque and tunneling magnetoresistance in antiferromagnetic tunnel junctions. These properties are crucial for the electrical writing and reading of information in antiferromagnetic spintronics.

“Our work has revealed an untapped potential of antiferromagnets and provided a straightforward solution to achieve efficient reading and writing for antiferromagnetic spintronics,” commented Professor Shao Ding-Fu.

Source: Hefei Institutes of Physical Science, Chinese Academy of Sciences

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