14 DAY TRIAL // In a groundbreaking experiment, investigators at the University of Minnesota, in the United States, recently managed to confirm the existence of giant saturation magnetization materials. In addition to this achievement, the group also managed to demonstrate that the predicted limit of maximum magnetism for an object can be indeed exceeded. In their investigation, the specialists used iron and nitrogen compounds, a mix of which, called Fe16N2, has been viewed as the Holy Grail of magnetic materials.
Generally, magnetism appears when the electrons around atoms in a certain material begin to exhibit the same spin orientation. Generally, this is either “up” or “down,” and whenever more of the electrons spin in one direction than the other, the material itself becomes magnetic. Based on this knowledge, physicists calculated that the most magnetic material theoretically possible is an iron-cobalt alloy. However, during the new investigations, the limit was exceeded.
The UM team demonstrated that their iron-nitrogen compound was about 18 percent more magnetic than the theoretical limits. They discover that this happens on account of the way atoms arrange themselves inside the new material. Using X-ray analysis, they determined that one nitrogen atom clustered six iron atoms around it, with another two atoms filling the gaps between clusters. While the iron atoms outside the clusters show regular magnetism, the ones inside experience a phenomenon known as “localization,” which means that their magnetism is boosted – hence the difference.
The new study was led by researcher Jian-Ping Wang, a professor at Electrical and Computer Engineering Department and the Center for Micromagnetics and Information Technologies (MINT). The work was based on a 1972 observation by Dr. M. Takahashi and a 1994 observation by Dr. Y. Sugita. Since then, this has been a 40-year mystery in magnetic materials and solid state physics communities because there is no theory and other experiments to support these observations.
That is to say, the material is metastable, and therefore tends to form a number of structures other than the compound. Until now, however, methods of fabricating this compound and fundamentally testing the idea have been underdeveloped. By using a new elemental magnetic specific observation technique called X-ray magnetic circular dichroism, the investigators were able to discover the unique “localized” electron states of iron atoms in Fe16N2 alone,More importantly, based on this discovery, the researchers have developed a theory to explain the giant saturation magnetization behavior of Fe16N2 based on the first-principles calculation, PhysOrg reports.