To make 2D alloy magnetic, replace a few atoms

(Credit: Getty Images)

Researchers have discovered that substituting atoms in the process of making two-dimensional alloys makes them customizable and magnetic.

Scientists used chemical vapor deposition (CVD) to make atom-thick sheets and, in the same step, tailor their properties by adding other elements through a process known as doping.

They discovered by surprise that they could also give the 2D sheets magnetic properties.

rhenium-doped molybdenum diselenide
An image of rhenium-doped molybdenum diselenide shows how the addition has rearranged the material’s atomic structure. The key shows the positions of rhenium atoms in blue, selenium in yellow, and molybdenum in red. (Credit: Oak Ridge National Laboratory)

The labs worked with transition metal dichalcogenides, alloys that combine a transition metal and chalcogen atoms into a single material. Transition metals are stable elements that fall in the middle of the periodic table. Chalcogens include sulfur, selenium, and tellurium, also neighbors to each other in the table.

By adding a dopant element to the mix during CVD, the researchers showed it was possible to rearrange the atoms on the resulting 2D crystal sheets. They demonstrated several different configurations and found they could replace some atoms outright with the dopant. These physical changes led to changes in the mechanical and electronic properties of the flat crystals, says Chandra Sekhar Tiwary, coauthor of the study and postdoctoral researcher at Rice University.

Pulickel Ajayan’s lab at Rice led the project to test theories by University of Southern California researchers who calculated that doping the materials would force a phase transition in the 2D crystals. The team confirmed the theory that adding rhenium in various amounts to molybdenum diselenide during growth would allow them to tailor its properties by changing its atomic structure. The magnetic signatures were a bonus.

Add 1 atomic layer to get magnetism

“Usually, when you make a magnetic material, you start with magnetic elements like iron or cobalt,” says Amey Apte, a graduate student and co-lead author of the study. “Rhenium, in bulk, is not a magnetic material, but it turns out it is in certain combinations at the atomic scale. It worked fantastically in this case.”

The researchers say the magnetic properties they discovered could make the 2D alloys of interest to those who design spintronic devices.

Researchers report their findings in the journal Advanced Materials.

Additional researchers contributing to the work are from Rice University, Oak Ridge National Laboratory, the University of Southern California, and Kumamoto University

The Computational Materials Science Program funded by the US Department of Energy, Office of Science, Basic Energy Sciences, supported the research.

Source: Rice University