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Researchers have found a way to merge the properties of ferromagnetic materials (whose atoms spin in the same direction) and antiferromagnetic materials (whose atoms spin in opposite directions and cancel out magnetism).
By applying just a small voltage, they were able to switch the direction in which the atoms of nickel iodide, an antiferromagnetic material, were spinning.
The ability to manipulate the spins of atoms could allow for the development of computer chips whose storage is based on spin rather than charge, allowing for much more space and longevity.
Magnetism can be a strange and powerful force. In an almost supernatural way, magnets stick to surfaces with no adhesives, which is why games like Etch-a-Sketch and Operation have fascinated generations of kids.
Most of what we see every day is ferromagnetism (think refrigerator magnets), the phenomenon describing how metals like iron and nickel are magnetized in a magnetic field and thus adhere to certain surfaces. There are also paramagnetic materials, like aluminum, which have a weak and almost unnoticeable attraction to magnets. There’s even antiferromagnetism—a type of magnetism in which magnetic atoms or ions in a material cancel their magnetism out if they end up next to each other.
And then there is a magnetism that is none of the above. By merging properties of ferromagnetic and antiferromagnetic materials, MIT physicists created a new kind magnetism that may someday revolutionize the memory chips that store data in laptops and smartphones. It’s called “p-wave magnetism,” and it makes use of the spin of atoms in a material rather than their charge to create magnetic properties.
“[This discovery] opens new opportunities for developing ultrafast, energy-efficient and high-endurance antiferromagnetic spintronic devices,” the researchers said in a study recently published in Nature.
The find is particularly huge for the field of spintronics. It might sound like a DJ spinning tracks on an alien planet—and, to be fair, it’s almost as far out—but it’s actually a scientific discipline centered around manipulating the spins of atoms in ferromagnetic and antiferromagnetic materials.
Atoms in ferromagnets are known to spin in the same direction, and as these atoms spin, so do their electrons. Those electrons, spinning furiously around their nuclei, generate magnetic fields that cause ferromagnets stick to some metals. On the other hand, neighboring atoms in antiferromagnets have opposite spins, which means the electrons generating their magnetic fields are spinning in opposite directions.
Antiferromagnets do not show visible magnetization, because the spins of their electrons and atoms cancel each other out—but the MIT team found a way around that. They synthesized nickel iodide (NiI2) in a lab and observed the behavior of the electrons in its atoms. Like a ferromagnet, the electrons did have one spin orientation they preferred, and like an antiferromagnet, there were enough electrons spinning in the opposite direction to cancel out magnetism. But there was something more.
It turned out that nickel atoms form spiral patterns that mirror each other, which made it possible to manipulate the spins of those atoms with a voltage. This caused some atoms to switch their spiral path from spinning left to right, and vice versa, turning the material into a p-wave magnet. And the electrons had their spins switched right along with the atoms as a whole in the same direction of that voltage.
This is how spintronics could seriously level up computer chips. With data taking the form of an electron’s spin rather than its charge, it leaves much more space for storage. Spintronics could mean chips able to store amounts of information orders of magnitude greater than anything currently available.
“The reported results represent the first observation of an electrically-switchable unconventional [opposite direction] magnet,” the researchers said. “These findings open a new frontier to realize symmetry-protected voltage-based switching of non-relativistic spin polarization in a compensated magnet.”
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