A group of physicists, led by Prof. SHAO Dingfu from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS), has predicted "parallel circuits" of spin currents in antiferromagnets, which can accelerate spintronics.
Spin-polarized electric currents play a central role in spintronics, due to the capabilities of manipulation and detection of magnetic moment directions for writing and reading 1s and 0s. Currently, most spintronic devices are based on ferromagnets, where the net magnetizations can efficiently spin polarize electric currents. Antiferromagnets, with opposite magnetic moments aligned alternately, are not quite as investigated but may promise even faster and smaller spintronic devices.
However, antiferromagnets have zero net magnetization and thus are commonly believed to carry solely spin-neutral currents useless for spintronics. While antiferromagnets consist of two antiparallel aligned magnetic sublattices, their properties are deemed to be "averaged out" over the sublattices, making them spin independently.
Prof. SHAO, however, envisioned that collinear antiferromagnets could function as "electrical circuits" with the two magnetic sublattices connected in parallel, provided they host strong coupling between magnetic atoms within the same sublattices. With this simple intuitive picture in mind, Prof. SHAO and his collaborators theoretically predicted that magnetic sublattices in such antiferromagnets could polarize the electric current locally, thus resulting in the staggered spin currents hidden within the globally spin-neutral current.
These staggered spin currents were dubbed as "Néel spin currents" after Louis Néel, a Nobel laureate, who won the prize due to fundamental work and discoveries concerning antiferromagnetism.
"The Néel spin currents is a unique nature of antiferromagnets, which has never been recognized," said Prof. SHAO. "It is capable to generate useful spin-dependent properties that have been previously considered incompatible with antiferromagnets, such as a spin-transfer torque and tunneling magnetoresistance in antiferromagnetic tunnel junctions, which are crucial for electrical writing and reading of information in antiferromagnetic spintronics."