Vanadium Iodine Found to be 2D Ferromagnetic Semiconductor

May 14, 2019 by Scott McMahan

Collaborating scientists at Princeton University, the U.S. Department of Energy's Ames Laboratory, and Brookhaven National Laboratory have identified a new layered ferromagnetic semiconductor, a rare type of material that holds great promise for next-generation electronic technologies.

Semiconductors that are closer to acting like an insulator than a metal are extraordinarily rare. The recent detection of ferromagnetism in semiconducting materials has been restricted to a handful of mostly chromium-based compounds.

However, the researchers discovered ferromagnetism in a vanadium-iodine semiconductor, a material which has long been known but ignored, a finding, which scientist Tai Kong compared to discovering a "hidden treasure in our own backyard."

Now serving as a postdoctoral researcher working in the lab of Robert J. Cava, the Russell Wellman Moore Professor of Chemistry at Princeton University, Kong completed his PhD research at the Ames Laboratory under supervision of Paul C. Canfield.

When it was found that the material could have a ferromagnetic response, Kong used Ames Laboratory for the magneto-optical visualization of magnetic domains that can provide the definitive proof of ferromagnetism.

"Being able to exfoliate these materials down into 2D layers gives us new opportunities to find unusual properties that are potentially useful to electronic technology advances," said Kong. "It's sort of like getting a new shape of Lego bricks. The more unique pieces you have, the cooler the stuff you can build."

The benefit of having ferromagnetism in a semiconductor is that electronic properties become spin-dependent, and electrons align their spins along internal magnetization.

"This creates an additional control knob to manipulate currents flowing through a semiconductor by manipulating magnetization, either by changing the magnetic field or by other more complex means, while the amount of current that can be carried may be controlled by doping (adding small amount of other materials)," said Ames Laboratory scientist Ruslan Prozorov. "These additional ways to control behavior and the potential to discover novel effects are the reason for such high interest in finding insulators and semiconductors that are also ferromagnets."

The research findings are revealed in the paper, "VI3—a New Layered Ferromagnetic Semiconductor," by Tai Kong, Karoline Stolze, Erik I. Timmons, et al. and featured on the back cover of Advanced Materials.

They found that the material becomes ferromagnetic at 49K. Below 49K with magneto‐optical Kerr effect imaging, they clearly observed ferromagnetic domains, which they said can be manipulated using an applied external magnetic field.

Ames Laboratory, which is operated by Iowa State University, is a U.S. Department of Energy Office of Science national laboratory.