Topological Insulators Offer Efficient Solution to Magnetic Memory

Researchers demonstrate that topological insulators are ten times as efficient as other materials at controlling magnetic memory

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Topological Insulators Offer Efficient Solution to Magnetic Memory
Photo: Fredric Weber/Penn State University

Since they were first theorized in 2005 and later experimentally produced in 2007, topological insulators, with their ability to insulate on the inside and conduct on the outside, present a tantalizing new class of materials for electronics applications. The hope has been that they can provide a simple way to manipulate an electron’s spin and further the field of “spintronics.”

While it has been proposed that materials like uranium and plutonium can be made to act as topological insulators, most topological insulators are made from alloys of bismuth.

In collaborative research led by researchers at Penn State and Cornell University, physicists have used the topological insulator bismuth selenide in combination with a standard ferromagnetic alloy material to create a material that is capable of controlling magnetic memory 10 times as efficiently as other combinations of materials.

"This is a really exciting development for the field because it is the first promising indication that we actually may be able to build a practical technology with these topological insulator materials, which many condensed-matter physicists have been studying with spintronics applications as the motivation," said Nitin Samarth, a professor of physics at Penn State, in a press release. "Our experiment takes advantage of the very special surface of bismuth selenide—a material that is a topological insulator—which inherently supports the flow of electrons with an oriented spin."

The Cornell side of the team discovered that at normal room temperatures, it is possible to use these spin-oriented electrons to efficiently control the direction of the magnetic polarity in the adjacent material.

"Our team's research has overcome one of the key challenges to developing a spintronics technology based on spin-orbit coupling -- the efficiency with which an ordinary charge current can be converted into a spin current," said Dan Ralph, the co-principal-investigator at Cornell University, in a press release.

The research, which was published in the journal Nature last week, set out to see if they could find an efficient way to reorient the magnetization of a magnetic material using the least amount of current and power. In their experiments, the researchers discovered that charge current flowing through a thin film of topological insulator can have a strong influence on the spin of electrons in the adjacent ferromagnetic material.

"The rapid progress shown in this field at Penn State and at laboratories around the world indicates that 'topological spintronics' shows great promise of becoming an attractive offshoot of more traditional approaches to spintronics technology,” Samarth added.

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