image: Design principle (a) The fundamental building block consists of magnetic atoms (arrows with circles) and polar molecules with PM, directed from the negative to the positive charge center. (b) Parallel (PP) and antiparallel (AP) PM establish magnetic sublattices related by translation and inversion symmetry, resulting in conventional AFM. (c) Noncollinear (NP) PM configurations connect magnetic sublattices via rotation symmetry, giving rise to AM with finite PS (assumed PS > 0 for clarity). Reversing one PM in the NP configuration (denoted as NP′) flips PS. (d) Schematic illustration of tuning PS through PM, where PM is indicated by the faucet handle, and PS by water drops with red (blue) for spin-up (-down). Twisting PM enables the switching PS on/off and reversing its sign.
Credit: ©Science China Press
Modern computers and memory chips rely on moving electric charges, but a new generation of technology called spintronics, aims to process information using the electron's spin instead. This could make devices faster, smaller, and far more energy-efficient. The challenge, however, has been how to precisely control spins using electric signals instead of power-hungry magnetic fields or electric currents.
A research team led by Tong Zhou from Eastern Institute of Technology, Ningbo, China, offers a promising breakthrough. The team focuses on a recently discovered class of materials called altermagnets—systems with no net magnetization but still showing a unique, momentum-dependent spin-splitting structure. This makes them as fast as antiferromagnets but as readily tunable and detectable as ferromagnets, an ideal combination for next-generation spintronics.
The researchers propose combining altermagnetism with molecular ferroelectrics, materials whose internal electric dipoles can be easily switched by voltage. These molecular systems are highly flexible: their tiny electric dipoles can align in various directions, allowing scientists to fine-tune both the strength and direction of electric polarization. This, in turn, can switch spin polarization on or off, or even reverse its sign—purely by applying an electric field, without changing the underlying magnetic order.
Using theoretical modeling and first-principles calculations, the team shows how this effect can be realized in hybrid organic–inorganic perovskites and metal–organic frameworks—both well-known and experimentally accessible materials. Their findings suggest a new class of molecular multiferroic altermagnets, where the orientation of the polar molecules can be tuned by external fields, enabling precise control of the electric and magnetic behaviors.
Although these organic altermagnets may not yet operate at room temperature, the concept is transformative: it could lead to ultra-low-power, electrically controlled spintronic devices. Coupling this approach with recent advances in antiferromagnetic tunnel junctions and spin-torque technologies might soon make electrically writable, multi-level magnetic memories a practical reality.
Journal
Science China Physics Mechanics and Astronomy
Method of Research
Computational simulation/modeling