Scientists have observed a completely new type of magnetic structure for the first time by using extremely short laser flashes to manipulate magnetism at the nanoscale.
The breakthrough, published in Nature Physics, could open new possibilities for future technologies that store and process information using magnetism instead of electricity.
The international study involved researchers from Sweden, Germany, Luxembourg, and China, including scientists at Uppsala University.
The newly observed structures are called magnetic hopfions. These are highly complex three-dimensional magnetic patterns formed by the spins of electrons inside a material.
Electron spin is a quantum property that acts somewhat like a tiny compass needle. In many magnetic materials, large numbers of spins align in simple ways, such as pointing up or down. But under certain conditions, spins can organize into much more complicated shapes.
Hopfions are especially unusual because the spins twist into closed loops that are linked together in three dimensions. Once formed, these structures are remarkably stable and tend to keep their shape even when disturbed.
Researcher Philipp Rybakov described hopfions as fascinating objects because they combine complex geometry with strong stability.
Although similar structures had previously been seen in some non-magnetic systems, magnetic hopfions had only existed in theoretical predictions until now. Scientists had struggled for years to create and observe them experimentally.
The key breakthrough came from using femtosecond laser pulses. A femtosecond is an incredibly short unit of time—just one millionth of a billionth of a second.
The researchers directed these ultrafast laser flashes onto thin films of iron germanium, a special magnetic material known as a chiral magnetic crystal. In chiral materials, the internal structure exists in two mirror-image forms, similar to left and right hands. This asymmetry strongly affects how magnetic spins organize themselves.
Normally, the magnetic system naturally settles into more ordinary states. But the laser pulses briefly disturbed the spins and pushed the material out of equilibrium, allowing entirely new magnetic structures to emerge.
After exposing the material to laser light, the team used advanced electron microscopy techniques to examine the resulting magnetic patterns. At the same time, they recreated the experiment using detailed computer simulations that modeled millions of interacting spins.
The simulations closely matched the experimental observations, confirming that the researchers had successfully created magnetic hopfions.
The scientists also used topology, a branch of mathematics that studies stable geometric properties such as knots and linked loops, to analyze and identify the structures.
In parallel research published in Nature Communications, scientists used the same laser-based method to create related two-dimensional magnetic structures called bimerons in another material. Together, the studies suggest that laser light could become a general tool for creating entirely new magnetic states in different materials.
The discovery could eventually benefit the field of spintronics, an emerging technology that uses electron spin instead of electric charge to store and process information. Because hopfions are stable and three-dimensional, they may offer new ways to design advanced memory devices and future computing technologies.
Researchers say the work also demonstrates how combining theory, experiments, computer simulations, and mathematics can reveal entirely new physical phenomena that were previously impossible to observe.
