This image shows the atomic landscape of chromium halides. The magnetic chromium atoms appear as gray spheres and the non-magnetic ligand atoms as green (chlorine), orange (bromine) and magenta (iodine) spheres. Image: Fazel Tafti.In a paper in Science Advances, a team led by researchers at Boston College reports that the magnetic properties of a chromium halide can be tuned by manipulating the non-magnetic atoms in the material. According to Fazel Tafti, assistant professor of physics at Boston College and a lead author of the paper, this seemingly counter-intuitive method is based on a mechanism known as an indirect exchange interaction.
An indirect interaction is mediated between two magnetic atoms via a non-magnetic atom known as the ligand. The Tafti Lab’s findings show that by changing the composition of these ligand atoms, all the magnetic properties can be easily tuned.
"We addressed a fundamental question: is it possible to control the magnetic properties of a material by changing the non-magnetic elements?" said Tafti. "This idea and the methodology we report on are unprecedented. Our findings demonstrate a new approach to create synthetic layered magnets with unprecedented level of control over their magnetic properties."
Magnetic materials are the backbone of many electronic technologies, such as the magnetic memory in our mobile devices. It is common practice to tune a material’s magnetic properties by modifying its magnetic atoms: for example, one magnetic element, such as chromium, can be replaced with another one, such as iron.
The researchers were studying ways to experimentally control the magnetic properties of inorganic magnetic materials, specifically chromium halides. These materials are made of one chromium atom, which is magnetic, and three non-magnetic halide atoms – chlorine, bromine and iodine.
This led them to discover a new method for controlling the magnetic interactions in layered materials based on a special interaction known as the ligand spin-orbit coupling. The spin-orbit coupling is a property of an atom to re-orient the direction of spins – the tiny magnets on the electrons – with the orbital movement of the electrons around the atoms.
This interaction controls the direction and magnitude of magnetism. Scientists have long been familiar with the spin-orbit coupling of the magnetic atoms in a material, but they did not know that the spin-orbit coupling of the non-magnetic atoms could also be utilized to re-orient the spins and tune the magnetic properties.
The researchers were surprised to find they could generate an entire phase diagram by modifying the non-magnetic atoms in a compound. "This finding puts forward a novel procedure to control magnetism in layered materials, opening up a pathway to create new synthetic magnets with exotic properties," Tafti said. "Moreover, we found strong signatures of a potentially exotic quantum state associated to magnetic frustration, an unexpected discovery that can lead to an exciting new research direction."
According to Tafti, the next step is to use these materials in innovative technologies such as magneto-optical devices or the new generation of magnetic memories.
This story is adapted from material from Boston College, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.