This simulation captures the different swirling textures of skyrmions and merons observed in a ferromagnet thin film. Image by the University of Edinburgh, UK, based on microscopy images collected by Argonne on samples prepared at MagLab.Microelectronics forms the foundation of much modern technology today, including smartphones, laptops and even supercomputers. It is based on the ability to allow and stop the flow of electrons through a material. Spin electronics, or spintronics, is a spinoff. Rather than the flow of electrons, it utilizes the spin of electrons, and the fact that the spin of an electron, along with its electric charge, creates a magnetic field.
“This property could be exploited for building blocks in future computer memory storage, brain-like and other novel computing systems, and high-efficiency microelectronics,” said Charudatta Phatak, group leader in the Materials Science division at the US Department of Energy (DOE)’s Argonne National Laboratory.
A team including researchers at Argonne and the National High Magnetic Field Laboratory (MagLab) has now discovered surprising properties in a magnetic material made of iron, germanium and tellurium. This material comes in the form of a thin sheet that is only a few to 10 atoms in thickness. It is called a 2D ferromagnet.
The team discovered that two kinds of magnetic fields can coexist in this ultrathin material. Scientists call them merons and skyrmions. They are like miniature swirling storm systems dotting the flat landscape of the ferromagnet. But they differ in their size and swirling behavior. The researchers report their findings in a paper in Advanced Materials.
Known and studied for about 15 years, skyrmions are about 100nm in size – approximately the same as a single virus molecule – and their magnetic fields flow in complicated patterns resembling those of the strands of a knot in a rope. Merons, on the other hand, were only recently discovered; they are roughly the same size as skyrmions but have magnetic fields that swirl around like whirlpools.
“Both skyrmions and merons are very stable because, like firmly tied knots, they are difficult to untangle,” said Luis Balicas, who holds a joint appointment at MagLab and Florida State University. “This stability along with their magnetic properties makes them attractive as carriers of information.”
The team is the first to observe both of these magnetic textures in a thin film at the same time at low temperatures, from -280°F to -155°F. Also, the merons remained present up to room temperature, an important consideration for exploiting them in practical devices. In the past, merons had only been observed at much lower temperatures in different materials.
The team also showed that skyrmions and merons are detectable from their effect on an applied current, by measuring the voltage. This feature means they are adaptable to the binary code used in all digital computers. This code consists of combinations of 1 and 0. In a spintronic device, a 1 would be indicated by an electrical signal detecting a skyrmion or meron. The absence of an electrical signal would then convey a 0.
Detecting and characterizing the different magnetic textures in a film less than ten atoms thick required a special scientific tool. Argonne physicist Yue Li met this challenging task using an instrument called a Lorentz transmission electron microscope (TEM), which includes aberration correction technology to improve its resolution. This microscope can visualize the magnetization of materials at the nanoscale under different magnetic fields over a wide temperature range, a unique capability available at Argonne. This range extends from -280°F to room temperature.
The team performed additional magnetic and other imaging at Argonne’s Center for Nanoscale Materials, a DOE Office of Science user facility.
“Much more basic research is needed to fully understand the behavior of skyrmions and merons under different conditions, and how to employ them in coding information,” Balicas said. “Many seemingly science fiction schemes are out there. We cannot predict the future, but it seems likely that one or more might come to fruition.”
This story is adapted from material from Argonne National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.