Scientists Unlock Hidden Magnetic Signals in Common Metals with Revolutionary Light-Based Technique
A groundbreaking new method allows researchers to detect subtle magnetic signals in everyday metals like copper, gold, and aluminum using only light, potentially revolutionizing fields from smartphone technology to the development of quantum computers. The findings, recently published in Nature Communications, overcome a century-old challenge in physics and open a new window into understanding electron behavior.
For over a century, scientists have understood the Hall effect – the tendency of electric currents to bend in a magnetic field. While pronounced in magnetic materials like iron, this effect is significantly weaker in non-magnetic metals. A related phenomenon, the optical Hall effect, theoretically offered a way to visualize electron behavior when interacting with light and magnetic fields, but remained undetectable at visible wavelengths due to its faintness.
“It was like trying to hear a whisper in a noisy room for decades,” explained a leading researcher involved in the study. “Everyone knew the whisper was there, but we didn’t have a microphone sensitive enough to hear it.”
Cracking the Code of Invisible Magnetism
The research, spearheaded by Ph.D. candidate Nadav Am Shalom and Professor Amir Capua at the Institute of Electrical Engineering and Applied Physics at Hebrew University, in collaboration with researchers from the Weizmann Institute of Science, Pennsylvania State University, and the University of Manchester, tackled the challenge of detecting these minute magnetic effects in non-magnetic materials.
“You might think of metals like copper and gold as magnetically ‘quiet’—they don’t stick to your fridge like iron does,” explained Professor Capua. “But in reality, under the right conditions, they do respond to magnetic fields—just in extremely subtle ways.” The core difficulty lay in developing a technique sensitive enough to observe these subtle responses, particularly using readily available visible light lasers.
Turning Up the Volume with Enhanced Kerr Effect
To overcome this hurdle, the team refined the magneto-optical Kerr effect (MOKE), a method that uses a laser to measure how magnetism alters light’s reflection. By combining a 440-nanometer blue laser with a significantly amplified modulation of the external magnetic field, they dramatically increased the technique’s sensitivity. This allowed them to detect magnetic “echoes” in metals like copper, gold, aluminum, tantalum, and platinum – a feat previously considered nearly impossible.
From Noise to Insight: Uncovering Hidden Quantum Properties
The new technique isn’t just about detection; it’s about understanding. Traditionally, measuring the Hall effect requires physically attaching wires to a device, a cumbersome process, especially at the nanoscale. This new approach simplifies the process, requiring only a laser beam directed at the electrical device.
Digging deeper into their data, the researchers discovered that what initially appeared as random “noise” actually followed a distinct pattern. This pattern was linked to spin-orbit coupling, a quantum property connecting electron movement and spin – a fundamental aspect of modern physics. This connection also provides insights into how magnetic energy dissipates within materials, with direct implications for the design of advanced technologies.
“It’s like discovering that static on a radio isn’t just interference—it’s someone whispering valuable information,” said Am Shalom. “We’re now using light to ‘listen’ to these hidden messages from electrons.”
A New Era for Materials Science and Beyond
This non-invasive, highly sensitive technique offers a powerful tool for exploring magnetism in metals without the need for large magnets or extremely cold temperatures. Its precision and simplicity could pave the way for faster processors, more energy-efficient systems, and sensors with unprecedented accuracy.
“This research turns a nearly 150-year-old scientific problem into a new opportunity,” said Professor Capua. Interestingly, the original discoverer of the Hall effect, Edwin Hall, attempted to measure the effect using light in 1881 but was unsuccessful, noting that the effect would only be detectable if the magnetic response of silver were ten times stronger than that of iron.
“By tuning in to the right frequency—and knowing where to look—we’ve found a way to measure what was once thought invisible.”
