For release: April 17, 2000
Contacts:
Saren Johnston, Public Affairs, (515) 294-3474
AMES, Iowa -- Researchers at the U.S. Department of Energy’s Ames Laboratory are
learning more about the behavior of unusual materials that may impact future technologies
thanks to the Lab’s new facility that takes environmental conditions to the extreme.
"In our new lab, we can study materials with respect to simultaneous extremes in
temperature, pressure and magnetic field," said Robert Modler, an Ames Laboratory
associate scientist and an Iowa State University assistant professor of physics and
astronomy. "If you want to analyze and understand the behavior of a new material,
ideally you would like to know as much as possible about how it reacts in this
three-dimensional parameter space. While quite a number of
researchers use one or two of these parameters to investigate materials, only a few really
put very low temperature, high magnetic field and high pressure together in one facility.
I would guess there are probably only five comparable facilities in the world."
As part of Ames Lab’s efforts to understand complex, novel materials, Modler is
studying exotic magnetic molecules, quasicrystalline materials, semimetals and new
magnetic superconductors, subjecting them to severe conditions in his lab of extreme
environments. Researchers at the Ames Laboratory hope to reveal the unique properties of
these materials properties that may prove to be good fits for potential applications in
fields that include computing technology, communications, medicine and the automotive
industry.
Working with ISU graduate students, Modler set up the new facility, incorporating a
3He-4He (helium three-helium four) dilution refrigerator, high-pressure cell and a
high-field superconducting solenoid to simultaneously create the three extreme
environments of very low temperature, high pressure and high magnetic field in one
instrument. Subjecting a material to the facility’s three-parameter environment
allows Modler and his co-workers to study the material in its "ground state,"
the low-temperature, lowest-energy state at which a material is almost completely free of
excitations and vibrations.
The near absence of temperature disturbances in the ground state allows the atoms in a
material to "calm down" and move about much more slowly, making it easier for
scientists to learn more about the material. Alternatively, by increasing the temperature
and taking the material out of its ground state, they can see what kind of excitations
develop and how they build up.
To achieve the ground state, the 3He-4He dilution refrigerator takes the material under
investigation through temperatures that range from 300 Kelvin (room temperature) to 0.05K
(just above absolute zero). Some intriguing "how cold is cold" facts may provide
insight on how "chilly" 0.05K might be.
"On the Kelvin scale, absolute zero, or 0K, is unreachable," said Modler.
"It would indicate the total absence of heat. As a comparison, our background
universe has an average temperature of about 3K, which stems from cosmic microwave
background radiation. In our lab, however, we reach 0.05K on a regular basis, which is
one-twentieth of a Kelvin above absolute zero. It’s an interesting thought that
temperatures this low have never naturally existed in our universe."
In addition to cooling a sample dramatically, Modler can further alter its environment by
applying high pressures of up to 20,000 atmospheres. Subjecting a material to high
pressures changes the distances between its atoms and can strongly affect or even
completely change its properties.
"One atmosphere is equal to the pressure resting on the surface of our earth,"
Modler explained. "Pressure of 20,000 atmospheres is equivalent to about 300,000
pounds per square inch. It can be thought of as approximately the weight of a Toyota Camry
on the tip of a medium-sized Phillips-head screwdriver."
The third parameter of Modler’s lab of extreme conditions is a powerful
superconducting magnet for magnetic fields up to 100,000 times that of the earth’s.
Just like high pressure, high magnetic field can cause abrupt changes in a material. It
can, for example, change how atoms are arranged in a magnetic material, causing a
different magnetic alignment -- a materials property perhaps most notably used in computer
hard disks.
"The parameters temperature, pressure and magnetic field are used for materials
research by many scientists throughout the world. But putting all three together in one
experiment might ‘scare’ even a tough material," said Modler. The materials
he is most interested in are those that exist close to a borderline between different
states, where altering the environmental parameters can cause drastic changes in their
physical properties. "By applying just enough pressure, magnetic field or both to
such a material, we can push it over the edge into a new state," he said.
"However, these materials are unusually complex; you might even call them
‘adaptive’ to their environments. To improve our scientific understanding of
them, we look very closely at how the changing states emerge from each other and how they
interact at the borderline. That’s something interesting and not well studied to this
point. And through our new facility, we can perform this research very
comprehensively."
Ames Laboratory is operated for the Department of Energy by ISU. The Lab conducts research
into various areas of national concern, including energy resources, high-speed computer
design, environmental cleanup and restoration, and the synthesis and study of new
materials.
Last revision: 9/23/03 kbg