'Fool's gold' may be valuable after all
For the first time, researchers electrically transform material from non- magnetic to magnetic

Date:
July 30, 2020
Source:
University of Minnesota
Summary:
In a breakthrough new study, scientists and engineers have
electrically transformed the abundant and low-cost non-magnetic
material iron sulfide, also known as 'fool's gold' or pyrite,
into a magnetic material.



FULL STORY ==========================================================================
In a breakthrough new study, scientists and engineers at the University
of Minnesota have electrically transformed the abundant and low-cost non-magnetic material iron sulfide, also known as "fool's gold" or pyrite,
into a magnetic material.


==========================================================================
This is the first time scientists have ever electrically transformed
an entirely non-magnetic material into a magnetic one, and it could
be the first step in creating valuable new magnetic materials for more energy-efficient computer memory devices.

The research is published in Science Advances, a peer-reviewed scientific journal published by the American Association for the Advancement of
Science (AAAS).

"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," said Chris Leighton, the lead researcher on
the study and a University of Minnesota Distinguished McKnight University Professor in the Department of Chemical Engineering and Materials Science.

Leighton and his colleagues, including Eray Aydil at New York University
and Laura Gagliardi (chemistry) at the University of Minnesota, have
been studying iron sulfide, or 'fool's gold,' for more than a decade for possible use in solar cells. Sulfur in particular is a highly abundant
and low-cost byproduct of petroleum production. Unfortunately, scientists
and engineers haven't found a way to make the material efficient enough
to realize low-cost, earth-abundant solar cells.

"We really went back to the iron sulfide material to try to figure out the fundamental roadblocks to cheap, non-toxic solar cells," Leighton said.

"Meanwhile, my group was also working in the emerging field of
magnetoionics where we try to use electrical voltages to control magnetic properties of materials for potential applications in magnetic data
storage devices. At some point we realized we should be combining these
two research directions, and it paid off." Leighton said their goal was
to manipulate the magnetic properties of materials with a voltage alone,
with very little electrical current, which is important to make magnetic devices more energy-efficient. Progress to date had included turning
on and off ferromagnetism, the most technologically important form of magnetism, in other types of magnetic materials. Iron sulfide, however,
offered the prospect of potentially electrically inducing ferromagnetism
in an entirely non-magnetic material.

In the study, the researchers used a technique called electrolyte
gating. They took the non-magnetic iron sulfide material and put
it in a device in contact with an ionic solution, or electrolyte,
comparable to Gatorade. They then applied as little as 1 volt (less
voltage than a household battery), moved positively charged molecules to
the interface between the electrolyte and the iron sulfide, and induced magnetism. Importantly, they were able to turn off the voltage and return
the material to its non-magnetic state, meaning that they can reversibly
switch the magnetism on and off.

"We were pretty surprised it worked," Leighton said. "By applying the
voltage, we essentially pour electrons into the material. It turns out
that if you get high enough concentrations of electrons, the material
wants to spontaneously become ferromagnetic, which we were able to
understand with theory. This has lots of potential. Having done it with
iron sulfide, we guess we can do it with other materials as well."
Leighton said they would never have imagined trying this approach if
it wasn't for his team's research studying iron sulfide for solar cells
and the work on magnetoionics.

"It was the perfect convergence of two areas of research," he said.

Leighton said the next step is to continue research to replicate the
process at higher temperatures, which the team's preliminary data suggest should certainly be possible. They also hope to try the process with
other materials and to demonstrate potential for real devices.


========================================================================== Story Source: Materials provided by University_of_Minnesota. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jeff Walter, Bryan Voigt, Ezra Day-Roberts, Kei Heltemes, Rafael M.

Fernandes, Turan Birol, Chris Leighton. Voltage-induced
ferromagnetism in a diamagnet. Science Advances, 2020; 6 (31):
eabb7721 DOI: 10.1126/ sciadv.abb7721 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200730092624.htm

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