First room-temp 'magnon switch' with industrially useful properties
Build approach could lead to entirely new and more efficient logic
switches for computer chips

Date:
June 15, 2020
Source:
National Institute of Standards and Technology (NIST)
Summary:
Scientists have demonstrated a practical technique for controlling
magnons, which could lead to computer chip switches that would use
less energy and radiate less heat. The approach brings two important
firsts: It can be built on silicon and operates efficiently at
room temperature, meaning it might be more readily employed by
computer manufacturers.



FULL STORY ========================================================================== Scientists at the National Institute of Standards and Technology (NIST)
and the Massachusetts Institute of Technology (MIT) have demonstrated
a potentially new way to make switches inside a computer's processing
chips, enabling them to use less energy and radiate less heat.


==========================================================================
The team has developed a practical technique for controlling magnons,
which are essentially waves that travel through magnetic materials
and can carry information. To use magnons for information processing
requires a switching mechanism that can control the transmission of a
magnon signal through the device.

While other labs have created systems that carry and control magnons, the team's approach brings two important firsts: Its elements can be built on silicon rather than exotic and expensive substrates, as other approaches
have demanded. It also operates efficiently at room temperature, rather
than requiring refrigeration. For these and other reasons, this new
approach might be more readily employed by computer manufacturers.

"This is a building block that could pave the way to a new generation
of highly efficient computer technology," said team member Patrick
Quarterman, a physicist at the NIST Center for Neutron Research
(NCNR). "Other groups have created and controlled magnons in materials
that do not integrate well with computer chips, while ours is built
on silicon. It's much more viable for industry." Magnons, also
called spin waves, would harness the property of electron spin to
transfer information. One reason computer chips get so hot is that in
a conventional circuit, electrons travel from one place to another, and
their movement generates heat. A magnon, however, moves through a long
string of electrons, which themselves do not need to travel. Instead,
each electron's spin direction -- which is a bit like an arrow stretching through the axis of a spinning top -- magnetically influences the spin direction of the next electron in line. Tweaking the spin of the first
electron sends a wave of spin changes propagating down the string. Because
the electrons themselves would not move, far less heat would result.

Because the electron string stretches from one place to another, the
magnon can carry information as it travels down the string. In chips
based on magnon technology, larger and smaller wave heights (amplitudes)
could represent ones and zeros. And because the wave height can change gradually, a magnon could represent values between one and zero, giving
it more capabilities than a conventional digital switch has.



========================================================================== While these advantages have made magnon-based information processing a tantalizing idea in theory, up until now most of the successful structures
have been built within multiple layers of thin films that sit atop a base
of gadolinium gallium garnet, rather than atop the silicon that commercial chips are made from. This "GGG" material would be prohibitively expensive
to mass produce.

"It's a fun physics playground that demonstrates the basic principles," Quarterman said, "but it's not practical for industrial-scale production." However, Yabin Fan and his colleagues at MIT used a creative engineering approach to layer the thin films atop a base of silicon. Their goal was
to build their system on top of the material that the computer industry
has been long accustomed to working with, thereby allowing magnons to
interface with conventional computer technology.

Initially, their multilayered creation did not behave as expected, but scientists at the NCNR used a technique called neutron reflectometry to
explore the magnetic behavior within the device. The neutrons revealed
an unexpected but advantageous interaction between two of the thin film
layers: Depending on the amount of magnetic field applied, the materials
order themselves in different ways that could represent a switch's "on"
or "off" state, as well as positions between on and off -- making it
akin to a valve.

"As you lower the magnetic field, the direction switches," said Fan, a postdoctoral associate in MIT's electrical engineering department. "The
data is very clear and showed us what was happening at different
depths. There's a very strong coupling between the layers." The magnon
switch could find use in devices that do another sort of calculating as
well. Conventional digital switches can only exist in either on or off
states, but because the amplitude of the spin wave can change gradually
from small to large, it is possible that magnons could be used in analog computing applications, where the switch has values lying between 0 and 1.

"That's why we consider this to be more like a valve," Quarterman
said. "You can open or close it a bit at a time."

========================================================================== Story Source: Materials provided by National_Institute_of_Standards_and_Technology_(NIST).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Y. Fan, P. Quarterman, J. Finley, J. Han, P. Zhang, J.T. Hou, M.D.

Stiles, A.J. Grutter and L. Liu. Manipulation of coupling and magnon
transport in magnetic metal-insulator hybrid structures. Physical
Review Applied, June 15, 2020 DOI: 10.1103/PhysRevApplied.13.061002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200615140917.htm

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