A New Breakthrough Makes Use of "Fool's Gold"

Scientists and engineers from the University of Minnesota have turned the naturally non-magnetic pyrite, or "fool's gold," into a magnetic material.

The breakthrough marks the transformation of a material's magnetic properties. Given the natural abundance of fool's gold, it could pave the way to the creation of new magnetic materials - and an application in improving memory devices in computers.

The work from the University of Minnesota, titled "Voltage-induced ferromagnetism in a diamagnet," is published in the peer-reviewed Science Advances.

Turning A Non-Magnet into A Magnet, Through Voltage

"Most people knowledgeable in magnetism would probably say it was impossible to electrically transform a non-magnetic material into a magnetic one. When we looked a little deeper, however, we saw a potential route, and made it happen," Chris Leighton said. Leighton is the lead researcher on the project and is a University of Minnesota Distinguished McKnight University Professor under the Chemical Engineering and Materials Science Department.

Leighton's team, which includes New York University's Eray Aydil and UMn's Laura Gagliardi, have been studying iron sulfide, also known as pyrite or "fool's gold,"for  more than a decade. They are looking at the material's possible applications in solar cells. In the report from the University of Minnesota website, it noted that the team has not yet found a way to make pyrite efficient enough to realize low-cost and earth-abundant solar cells.

They grew Pyrite FeS2 crystals through chemical vapor transport. Researchers then used a technique called electrolyte gating. The naturally non-magnetic iron sulfide crystals are placed in contact with an electrolyte solution. A small voltage was applied and moved positive ions to the interface placed between the electrolyte and the iron sulfide, inducing magnetism. Furthermore, when they removed the applied voltage, the observed magnetism in the pyrite crystal was also removed. 

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Implications of Electrically Transforming A Material's Magnetic Properties

"We were pretty surprised it worked," Leighton said. He explained that applying voltage is equivalent to increasing the electron concentration on the material. Leighton added that "upon crossing a certain threshold, the material "wants to spontaneously become ferromagnetic, which we were able to understand with theory.

"It was the perfect convergence of two areas of research," Leighton noted, recognizing the contribution of their iron sulfide for solar application studies.

The research team has achieved voltage-controlled magnetism for the iron sulfide crystal. Leighton also added that the next step for their study is to try and replicate the voltage-induced ferromagnetism at higher temperatures. According to their preliminary data, the researchers are confident that the same behavior can be achieved under the new conditions.

Pyrite, known as fool's gold, is among the world's most abundant sulfide minerals. One of its components, Sulfur, is also a highly-abundant material, often a byproduct of petroleum production. Its pale yellow metallic hue gives it a physical resemblance to gold, hence its nickname of "fool's gold." Historically, pyrite has been used as a source of ignition especially in the 16th and 17th centuries. In the modern times, pyrite is sourced as the cathode substance in non-rechargeable lithium batteries.

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