You might think that magnetism is as simple as a north pole and a south pole attracting each other. Yet this phenomenon, silently omnipresent in our daily life, still isn't completely understood, as evidenced by a new study from physicists at the University of Illinois at Urbana-Champaign.
Magnetic fields are created whenever electric charges move, most commonly when electrons spin around themselves. But electrons also orbit around the nucleus of an atom, much like the Earth orbits around the sun. This creates another magnetic field. The combination of the magnetic field from the spin with the magnetic field from the orbiting creates and effect called the spin-orbit torque. This causes electrons in a current to shear off to opposite sides of a film depending on their spins. Electrons spinning clockwise might move to the top of the sheet, and those spinning anticlockwise to the bottom.
Scientists previously thought that to create the spin-orbit torque, another metal touching the magnetic film was needed, but this new study suggests otherwise. To show this, the researchers passed a current from one edge of a magnetic film to the other and measured the spin of the electrons on both sides by shining light onto the film. Since the magnetic surface actually changes the direction of light's vibrations, they could then measure the reflected light to infer the direction of magnetization. It sounds complicated, but the press release for the paper makes it clear that this is "indisputable evidence" in favor of the phenomenon observed, which is called "anomalous spin-orbit torque."
It is exciting that even for something as well-studied as magnetism, we still have discoveries to make. And this research could lead to advances in magnetic-memory technology, which will make computer memory storage faster and more energy-efficient.