Physicists detect hidden 'octupolar' magnetism using rotating light

Overview

Updated 55 minutes ago

Two-pole magnets run the modern world. Hard drives, credit-card strips, and refrigerator doors all rely on the familiar north-south dipole. A University of Toronto team has now found a way to see a stranger magnetic state, one that behaves as if it has eight poles and that ordinary instruments cannot detect.

The method bounces rotating light off a crystal and reads the handedness of its atomic vibrations. If it holds up on real materials, engineers could store data in magnetic states that barely leak field into their neighbors, which means denser, more stable memory and new quantum devices.

Why it matters

Octupolar magnetism could shrink data-storage bits, which today are limited because dipole magnets spill fields into neighboring cells.

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Key Indicators

Poles in the hidden octupolar order

The crystal behaves as if it has eight magnetic poles rather than the familiar two.

Poles in a conventional magnet

Bar and fridge magnets are dipolar, with a north and a south pole.

New optical probe reported

The rotating-light method reads magnetic order that standard measurement techniques miss.

Voices

Curated perspectives — historical figures and your fellow readers.

Ever wondered what historical figures would say about today's headlines?

People Involved

Arun Paramekanti

Senior author of the study; professor of physics at the University of Toronto

Professor, Department of Physics and Center for Quantum Information & Quantum Control, University of Toronto

Ruairidh "Rory" Sutcliffe

Lead author; PhD candidate in physics at the University of Toronto

PhD candidate, Department of Physics, University of Toronto

Swati Chaudhary

Co-author; project research associate at the University of Tokyo

Project research associate, University of Tokyo

Kathleen Hart

Co-author; PhD candidate in physics at the University of Toronto

PhD candidate, Department of Physics, University of Toronto

Organizations Involved

University of Toronto

Public research university

Home of the team that devised the optical detection method

A public research university in Toronto, Canada, and home of the quantum physics group behind the octupolar magnetism detection method.

University of Tokyo

Public research university

Affiliation of co-author Swati Chaudhary

A public research university in Tokyo; co-author Swati Chaudhary is a project research associate there.

Timeline

June 2025 September 2026

2 events Latest: 6 days ago

September 2026
Physical Review Letters publishes octupolar detection method
Latest Publication

The study reports that rotating light reveals hidden eight-pole magnetic order through pseudo-chiral phonons.
6 days ago
June 2025
Pseudo-chiral phonon paper posted to arXiv
Publication

Researchers posted a preprint describing how octupolar order imprints handedness on crystal vibrations.
June 2025

Scenarios

Octupolar signature found in a real crystal

Likely Resolves by End of 2027

Discussed by: The Toronto team and condensed-matter researchers studying multipolar order; coverage notes the next test is whether the signature shows up in candidate crystals

Experiments would point the rotating-light probe at materials predicted to host octupolar order and report the pseudo-chiral phonon signature. That would give physicists a practical way to map a class of magnetic order that has so far been inferred mostly indirectly.

Working memory device built on octupolar order

Possible Resolves by End of 2029

Discussed by: Paramekanti's group, which cites controllable read-write memory elements as the target application

If the optical signal can read octupolar order and phonons can switch it, engineers could build memory bits that pack tightly because they leak almost no stray field. This is the longer-term payoff and depends on the detection method surviving contact with real materials.

Signature fails to appear in candidate materials

Possible Resolves by End of 2027

Discussed by: Researchers noting how hard octupolar order has been to confirm in real substances

The predicted vibration handedness could prove too weak or be masked by other effects when tested in actual crystals. That outcome would leave octupolar order as a theoretical curiosity until a different probe appears.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

1930s–1949

Antiferromagnetism and neutron diffraction (1930s–1949)

Louis Néel predicted antiferromagnetism in the 1930s, a magnetic order with no net magnetization that ordinary magnetic measurement could not see. Clifford Shull confirmed it in 1949 by scattering neutrons off the atomic spin arrangement in manganese oxide.

Then

Neutron diffraction verified Néel's theory and gave researchers a way to see magnetic structure directly.

Now

Shull shared the 1994 Nobel Prize in Physics, and neutron scattering became a standard tool for mapping magnetic order.

Why this matters now

Antiferromagnetism was hidden to ordinary probes for decades until a new measurement technique appeared. Octupolar order sits in the same position today, with the rotating-light method proposed as its neutron-scattering moment.

2022–2024

Altermagnetism predicted then observed (2022–2024)

In 2022, Libor Šmejkal, Jairo Sinova, and Tomas Jungwirth proposed altermagnetism, a new class of magnetic order with a distinctive spin-splitting signature. Photoemission experiments in 2024 captured that splitting in materials such as manganese telluride, confirming the class.

Then

Altermagnets went from theory to experimental confirmation within about two years.

Now

The class is now studied as a candidate for spintronics and other devices.

Why this matters now

Researchers have explicitly tied magnetic octupoles to d-wave altermagnets, so octupolar order extends the same line of work. That history suggests theory-to-detection gaps in magnetism can close quickly once a good probe exists.