Beyond Silicon: How New Materials Move Spintronics Towards Reality
"Today's semiconductors are made of
crystals with simple, symmetrical patterns, like a microscopic lattice that repeats over and over," he said. "We control the properties of those semiconductors by adding atoms of different elements to the holes in that lattice. For example, we can add bismuth to
increase conductivity, or iron to increase
magnetism. To make spintronic
semiconductors, we need to add atoms of different sizes, and we need flexibility in where we place those atoms. But in most commonly used crystals, the holes are all similarly sized and regularly spaced. That gives us a very limited amount of control."
Researchers have been working for years to solve this problem by finding new ways to add atoms to commonly used crystalline structures. But Poudeu's team took a
different approach, creating an entirely new crystal structure. They used a mixture of iron, bismuth and selenium to create a complex crystal that offers much greater flexibility. Their low-symmetry crystal has holes of
varying size placed at varying distances in multiple, overlapping layers.
"Ordinarily, conductivity and magnetism are linked together, so you can't change one without affecting the other," said Juan Lopez, a doctoral student in materials science and engineering working on the project. "But this new compound changes that. It enables us to arrange atoms in a huge number of
different combinations so that we can
manipulate conductivity and magnetism
independently. That level of control is going to open a whole new set of possibilities."
Lopez said the project's cross-disciplinary team has brought a fresh perspective to the project, combining chemistry, crystallo-
graphy and computer science to build a new solution to a problem that has vexed
researchers for years.