You’ve probably heard of ferromagnetism,
materials that become magnetic in a magnetic field, but have you heard of ferroelectricity? And what do hysterons have to do with it? Wait what are hysterons anyway? Ok I’m getting ahead of myself, let’s
go back to ferroelectricity. Ferroelectricity isn’t related to iron like
you might think, but it gets its name because it’s analogous to ferromagnetism. Ferromagnetic materials like iron are made
up of magnetic domains that have north and south poles. If these domains line up, the material itself
becomes magnetic. Likewise ferroelectric materials are made
of crystals that are electric dipoles, meaning they have a separated positive and negative
charge. If these dipoles line up, the material itself
will have a positive and negative pole. Usually the dipoles are pointing in random
directions, but they can be coerced into uniformity. The same way iron’s domains can line up
when exposed to a strong enough external magnetic field, a ferroelectric’s dipoles will line
up when exposed to a strong enough electric field. They’ll stay that way when the field is
removed, as though they have a memory, and because of that memory when another electric
field is applied that can change the dipole’s directions they’ll lag behind orienting
to the new field, a phenomenon called hysteresis. In a ferroelectric material the switch doesn’t
happen all together like it ideally should, different parts of it change direction at
different times. Figuring out exactly why took more than 80
years of searching. In 1935 a german researcher mathematically
described ferroic materials as small independent parts called hysterons. Each hysteron would change it’s polarization
at a well defined speed when exposed to a strong enough field, but each hysteron could
also have a different critical field than its neighbors. Meaning a magnetic or electric field that
was strong enough to change one hysteron would have no effect on the hysteron next to it. The model works and accurately describes the
behavior of ferroelectrics, but nobody was sure what hysterons actually were and the
physics of why they behaved that way. That was until 2018, when researchers studied
two organic ferroelectric materials and observed stacks of disc-shaped molecules a few nanometers
high. The stacks’ different sizes and tight packing
meant they all strongly interacted with each other, causing them to react differently to
the different field strengths. Finally, we witnessed hysterons and confirmed
why ferroelectrics line up their dipoles at the speed they do. That wasn’t the only breakthrough in our
understanding of ferroelectrics in 2018. I know, you just learned about them and they’re
already advancing at a breakneck pace. See, ferroelectrics can be permanently polarized,
meaning their dipoles stay aligned even after the field is removed, until another critical
field aligns them in another direction. That property means they have a potential
use in computer storage. Many computers today still use a magnetic
hard drive to store data, but creating a magnetic field requires a large current. Ferroelectrics could use less power to store
data, but until recently they had a scaling problem. The crystals could only get so small until
the aligned dipoles became unstable. Roughly eight years ago though, researchers
in germany claimed they made a ferroelectric material that did the opposite: it kept it’s
dipoles aligned when thinner than 10 nanometers, but when it got thicker it lost its ferroelectric
properties. A group of skeptical scientists tried to simplify
the material and recreate the results, and much to their surprise they did. In fact their results were even better than
before. It turns out at that small scale, the crystals
were under immense pressure that caused a different arrangement of their structures
and a polar phase. As an added bonus the substrate used to grow
the crystals was also magnetic, opening up the possibility of magnetic and ferroelectric
storage on the same drive, allowing for more data can be stored in the same space. Don’t expect ferroelectric computer storage
to hit shelves tomorrow, there’s a lot more hurdles the technology would have to clear. But If one day in the future, you’re shopping
for a new computer and you start seeing the flashy marketing term “Ferroelectric hard
drive,” just remember you heard it here first. Computer storage is one area where a lot of
different fields of study have a lot of promise, like the potential to store data on a single
atom. Check out my video on that here. Those tiny lab grown crystals had pressures
up to 5 gigapascals inside the crystal, or over 49,000 times the atmospheric pressure
at sea level. Thanks for watching, don’t forget to subscribe,
no pressure, and I’ll see you for more Seeker.