What happened
- A team from CIC nanoGUNE and the University of the Basque Country, in San Sebastián, together with the Institute of Physics of the Czech Academy of Sciences and Charles University in Prague, reported in Nature on October 28, 2026 the electrical injection of spins from Mn5Si3, a compensated magnet with no net magnetization.
- They used lateral spin-valve devices: they injected spins from Mn5Si3 into a non-magnetic channel and detected their arrival at a separate ferromagnetic electrode.
- When they flipped the magnetic state of Mn5Si3, the detected spin signal flipped too. That shows the injection breaks time-reversal symmetry, a signature different from known methods.
- The team’s calculations give spin polarizations of 6.5% to 10%, comparable to those of conventional ferromagnets.
Why it matters
- Spintronics processes information with the spin of electrons, not only their charge. Until now, spin currents came from ferromagnets, which have net magnetization, or from relativistic effects such as the spin Hall effect.
- Ferromagnets have a drawback for miniaturization: their magnetic field disturbs neighbors, which limits how close bits can be packed. A material with no net magnetization does not have that problem.
- Altermagnets, a class of materials proposed in recent years, promise to combine two advantages: spin-polarized currents without an external magnetic field. This experiment is an electrical demonstration of that promise in a device.
- The behavior was seen in two different electrical biasing geometries, which supports that it is not an artifact of the setup.
The number
6.5% to 10%. That is the spin polarization the calculations assign to Mn5Si3, in the same range as the ferromagnets used today.
Context
In a ferromagnet such as iron, electron spins line up and add up to a net magnet. In an antiferromagnet they alternate and cancel. Altermagnets also cancel their total magnetization, but their crystal structure gives electrons moving in certain directions a preferred spin.
The team combined symmetry analysis, first-principles calculations and spin-transport modeling. According to the paper, the observations are consistent with the altermagnetic order of Mn5Si3, a manganese and silicon compound.
The industrial relevance lies in magnetic memories and sensors. A spin injector without stray fields could allow denser memory cells that are less sensitive to outside fields.
What’s next
- The experiment shows the principle in lab devices; efficiency, operating temperature and compatibility with chip manufacturing still have to be measured.
- The logical next step is to use the altermagnet as a detector as well, without ferromagnetic electrodes.
Bottom line
Materials physics is bringing new ways to move electrons: Columbia trapped electron waves in a metal by interference and a helicene turns like an Archimedes screw with current. Chirality also shows up in supertwisted WS₂ layers and in Smith-Purcell radiation on a silicon grating.
Sources
- Nature — Time-reversal-symmetry-breaking spin injection from a compensated magnet (Mencos et al., October 28, 2026)
- Cover image: Eric Gaba (Sting), CC BY-SA 3.0, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
