Nanoscale spin waves can replace microwaves
Spin
waves spread from a magnetic nanocontact like rings on water. Credit:
University of Gothenburg
A group of scientists from the
University of Gothenburg and the Royal Institute of Technology (KTH), Sweden,
have become the first group in the world to demonstrate that theories about
nanoscale spin waves agree with observations. This opens the way to replacing
microwave technology in many applications, such as mobile phones and wireless
networks, by components that are much smaller, cheaper, and that require less
resources. The study has been published in the scientific journal Nature Nanotechnology, the most
prestigious journal in nanoscience.
"We
have been in competition with two other research groups to be the first to
confirm experimentally theoretical
predictions that were first made nearly 10 years ago. We have
been successful due to our method for constructing magnetic nanocontacts and
due to the special microscope at our collaborators' laboratory at the
University of Perugia in Italy", says Professor Johan Åkerman of the
Department of Physics, University of Gothenburg, where he is head of the Applied
Spintronics group.
The aim
of the research project, which started two years ago, has been to demonstrate
the propagation of spin waves from
magnetic nanocontacts. Last autumn, the group was able to demonstrate the
existence of spin waves with the aid of electrical measurements, and the
results were published in the scientific journal Physical Review Letters. The
new results have been published in Nature Nanotechnology, the most prestigious
journal in nanoscience.
The
simulation of magnetic nanocontacts shows how spin waves spread like rings on
water. The nanocontact has a diameter of 40 nanometre and the spin waves are
created in a thin film of nickel-iron alloy, 3 nanometre thick.
The
research group has used one of the three advanced spin wave microscopes in the
world, at the university in the Italian town of Perugia, to visualise the
motion. The microscope makes it possible to see the dynamic properties of
components with a resolution of approximately 250 nanometre.
The
results have opened the way for a new field of research known as
"magnonics", using nanoscale magnetic waves.
"I
believe that our results will signal the start of a rapid development of
magnonic components and circuits. What is particularly exciting is that these
components are powered by simple direct current, which is then converted into
spin waves in the microwave region. The frequency of these waves can be
directly controlled by the current. This will make completely new functions
possible", says Johan Åkerman, who is looking forward to exciting
developments in the next few years.
A
simulation of six magnetic nanocontacts placed in a circle to illustrate how
the nanocontacts can be placed in freely chosen patterns. All the signals
synchronise in this case through the spin waves that propagate through the
magnetic film.
Its
magneto-optical and metallic properties mean that magnonic technology can be
integrated with traditional microwave-based electronic circuits, and this will
make completely untried combinations of the technologies possible. Magnonic
components are much more suitable for miniaturisation than traditional microwave technology.
Nanocables light way to the future: Researchers power line-voltage light
bulb with nanotube wire
![Nanocables light way to the future: Researchers power line-voltage light bulb with nanotube wire](file:///C:%5CDOCUME%7E1%5CDLIB-S%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_image001.jpg)
A power
cable made entirely of iodine-doped double-walled carbon nanotubes is just as
efficient as traditional power cables at a sixth the weight of copper and
silver, according to researchers at Rice University. (Credit: Yao Zhao/Rice
University)
(PhysOrg.com) -- Cables made of
carbon nanotubes are inching toward electrical conductivities seen in metal
wires, and that may light up interest among a range of industries, according to
Rice University researchers.
A Rice
lab made such a cable from double-walled carbon nanotubes and powered a
fluorescent light bulb at standard line voltage -- a true test of the novel
material's ability to stake a claim in energy systems of the future.
The work
appears this week in the Nature journal Scientific
Reports.
Highly
conductive nanotube-based cables could be just as efficient as traditional metals
at a sixth of the weight, said Enrique Barrera, a Rice professor of mechanical
engineering and materials science. They may find wide use first in applications
where weight is a critical factor, such as airplanes and automobiles, and in
the future could even replace traditional wiring in homes.
The
cables developed in the study are spun from pristine nanotubes and can be tied
together without losing their conductivity. To increase conductivity of the
cables, the team doped them with iodine and the cables remained stable. The
conductivity-to-weight ratio (called specific conductivity) beats metals,
including copper and silver, and is second only to the metal with highest
specific conductivity, sodium.
Yao Zhao,
who recently defended his dissertation toward his doctorate at Rice, is the new
paper's lead author. He built the demo rig that let him toggle power through
the nanocable and replace conventional copper wire in the light-bulb circuit.
Zhao left
the bulb burning for days on end, with no sign of degradation in the nanotube
cable. He's also reasonably sure the cable is mechanically robust; tests showed
the nanocable to be just as strong and tough as metals it would replace, and it
worked in a wide range of temperatures. Zhao also found that tying two pieces
of the cable together did not hinder their ability to conduct electricity.
The few
centimeters of cable demonstrated in the present study seems short, but
spinning billions of nanotubes (supplied by research partner Tsinghua
University) into a cable at all is quite a feat, Barrera said. The chemical
processes used to grow and then align nanotubes will ultimately be part of a
larger process that begins with raw materials and ends with a steady stream of
nanocable, he said. The next stage would be to make longer, thicker cables that
carry higher current while keeping the wire lightweight. "We really want
to go better than what copper or other metals can offer overall," he said.
The
paper's co-authors are Tsinghua researcher Jinquan Wei, who spent a year at
Rice partly supported by the Armchair Quantum Wire Project of Rice University’s
Smalley Institute for Nanoscale Science and Technology; Robert Vajtai, a Rice
faculty fellow in mechanical engineering and materials science; and Pulickel
Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Mechanical
Engineering and Materials Science and professor of chemistry and chemical and
biomolecular engineering
World's smallest electric motor made from a single molecule
![World's smallest electric motor made from a single molecule](file:///C:%5CDOCUME%7E1%5CDLIB-S%7E1%5CLOCALS%7E1%5CTemp%5Cmsohtmlclip1%5C01%5Cclip_image002.jpg)
Chemists
at Tufts University have developed the world's first single molecule electric
motor, which may potentially create a new class of devices that could be used
in applications ranging from medicine to engineering. The molecular motor was
powered by electricity from a state of the art, low-temperature scanning
tunneling microscope. This microscope sent an electrical current through the
molecule, directing the molecule to rotate in one direction or another. The
molecule had a sulfur base (yellow); when placed on a conductive slab of copper
(orange), it became anchored to the surface. The sulfur-containing molecule had
carbon and hydrogen atoms radiating off to form what looks like two arms
(gray); these carbon chains were free to rotate around the central
sulfur-copper bond. The researchers found that reducing the temperature of the
molecule to five Kelvin (K), or about minus 450 degrees Fahrenheit (ºF),
enabled them to precisely impact the direction and rotational speed of the
molecular motor The Tufts team plans to submit this miniature electric motor to
the Guinness World Records. The research was published online Sept. 4 in Nature Nanotechnology. Credit:
Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin
V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov and E.
Charles H. Sykes.
Chemists at Tufts University's
School of Arts and Sciences have developed the world's first single molecule
electric motor, a development that may potentially create a new class of devices
that could be used in applications ranging from medicine to engineering.
In
research published online September 4 in Nature
Nanotechnology, the Tufts team reports an electric motor that measures
a mere 1 nanometer across, groundbreaking work considering that the current
world record is a 200 nanometer motor. A single strand of human hair is about
60,000 nanometers wide.
According
to E. Charles H. Sykes, Ph.D., associate professor of chemistry at Tufts and
senior author on the paper, the team plans to submit the Tufts-built electric
motor to Guinness World Records.
"There
has been significant progress in the construction of molecular motors powered
by light and by chemical reactions, but
this is the first time that electrically-driven molecular motors have been
demonstrated, despite a few theoretical proposals," says Sykes. "We have
been able to show that you can provide electricity to a single molecule and get
it to do something that is not just random."
Sykes and
his colleagues were able to control a molecular motor with
electricity by using a state of the art, low-temperature scanning tunneling
microscope (LT-STM), one of about only 100 in the United
States. The LT-STM uses electrons instead of light to "see" molecules.
The team
used the metal tip on the microscope to provide an electrical charge to a
butyl methyl sulfide molecule that had been placed on a conductive copper surface. This
sulfur-containing molecule had carbon and hydrogen atoms
radiating off to form what looked like two arms, with four carbons on one side
and one on the other. These carbon chains were free to rotate around the
sulfur-copper bond.
The team
determined that by controlling the temperature of the molecule they could
directly impact the rotation of the molecule. Temperatures around 5 Kelvin (K), or
about minus 450 degrees Fahrenheit (ºF), proved to be the ideal to track the
motor's motion. At this temperature, the Tufts researchers were able to track
all of the rotations of the motor and analyze the data.
While
there are foreseeable practical applications with this electric motor, breakthroughs
would need to be made in the temperatures at which electric molecular motors
operate. The motor spins much faster at higher temperatures, making it
difficult to measure and control the rotation of the motor.
"Once
we have a better grasp on the temperatures necessary to make these motors
function, there could be real-world application in some sensing and medical
devices which involve tiny pipes. Friction of the fluid against the pipe walls
increases at these small scales, and covering the wall with motors could help
drive fluids along," said Sykes. "Coupling molecular motion with
electrical signals could also create miniature gears in nanoscale electrical
circuits; these gears could be used in miniature delay lines, which are used in
devices like cell phones."
The
Changing Face of Chemistry
Students
from the high school to the doctoral level played an integral role in the
complex task of collecting and analyzing the movement of the tiny molecular
motors.
"Involvement
in this type of research can be an enlightening, and in some cases life
changing, experience for students," said Sykes. "If we can get people
interested in the sciences earlier, through projects like this, there is a
greater chance we can impact the career they choose later in life."
As proof
that gaining a scientific footing early can matter, one of the high school
students involved in the research, Nikolai Klebanov, went on to enroll at
Tufts; he is now a sophomore majoring in chemical engineering.
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