Physicists solve decades-old puzzle in how magnetic materials conduct electricity

For years, physicists have been puzzled by a strange effect in magnetic materials: when magnetization rotates in certain directions, electrical resistance changes in ways that shouldn't happen according to the prevailing theory. Researchers thought they'd found the answer in something called spin Hall magnetoresistance — but the experiments kept telling a different story.

Now, scientists from the Institute of Semiconductors at the Chinese Academy of Sciences and the Chinese University of Hong Kong have figured out what's actually going on. The effect isn't caused by spin currents, as the leading theory suggested. Instead, it comes from something simpler: electrons scattering at the boundaries between different materials, influenced by the magnetization and the electric field sitting right at that interface.

This matters because spintronics — using electron spin to store and process information — is the foundation for next-generation computing and memory devices. Getting the physics right is how you build better technology. The old framework had created a gap between what theory predicted and what experiments showed. That gap is now closed.

What the evidence revealed

The research team conducted precise measurements showing that this two-vector magnetoresistance effect (as they call it) can produce enormous resistance changes even in single-layer magnetic metals — materials so thin they're just one atomic layer thick. Their data followed a universal pattern, matching mathematical predictions that the old spin Hall model couldn't explain.

When the researchers went back through decades of published experiments, they found that the most reliable data — the measurements everyone had been citing — actually fit the new framework perfectly. It was a moment of scientific clarity: one simple mechanism, not multiple competing theories, explained the whole phenomenon.

"This fundamentally challenges" the widely accepted spin Hall magnetoresistance theory, the team wrote in their paper, published in National Science Review in June 2025. That's measured language for a major revision of how physicists understand magnetoresistance.

The breakthrough matters beyond the lab. If you're designing spintronic devices — sensors, memory chips, processors — you need to know which forces are actually controlling how electrons move. The old model was like trying to fix a car when you're looking at the wrong part of the engine. Now researchers have the right part in focus.

What comes next is the practical work: engineers can now design better magnetic materials and interfaces, knowing exactly which properties to control. The unified framework gives them a clearer roadmap.