A novel material that may demonstrate a highly unusual
"liquid" magnetic state at extremely low temperatures has
been discovered by a team of Japanese and U.S. researchers,
according to a study published in the Sept. 9 issue of
The material, nickel gallium sulfide, known as
NiGa2S4, was synthesized by scientists at Kyoto University.
Its properties were studied by the Japanese team and by
researchers from Johns Hopkins and the University of
Maryland at the Commerce Department's National Institute of
Standards and Technology.
The scientists studied the polycrystalline sample
using both X-rays and neutrons as probes to understand its
structure and properties. The neutron experiments were
conducted at the NIST Center for Neutron Research in
The team found that the triangular arrangement of the
material's atoms appears to prevent alignment of magnetic
"spins," the characteristic of electrons that produces
magnetism. A "liquid" magnetic state occurs when magnetic
spins fluctuate in a disorderedly, fluidlike arrangement
that does not produce an overall magnetic force. The state
was first proposed as theoretically possible about 30 years
ago. A liquid magnetic state may be related to the
similarly fluid way that electrons flow without resistance
in superconducting materials.
According to Johns Hopkins'
Broholm, a professor in the Krieger School's
Department of Physics
and Astronomy, "The current work shows that at an
instant in time the material looks like a magnetic liquid,
but whether there are fluctuations in time, as in a liquid,
remains to be seen."
Each electron can be thought of as a tiny bar magnet.
The direction of its "north" pole is its spin. "An ordered
pattern of spins generally uses less energy," Broholm said,
"but the triangular crystal structure prevents this from
happening in this material."
The team conducted its neutron experiments with a disk
chopper spectrometer, the only instrument of its kind in
North America. The instrument sends bursts of neutrons of
the same wavelength through a sample; more than 900
detectors arranged in a large semicircle then determine
exactly where and when the neutrons emerge, providing
information key to mapping electron spins.
"The energy range and resolution we can achieve with
this instrument is ideal for studying magnetic systems,"
Yiming Qiu, a NIST guest researcher from the University of
The wavelength of the slowed-down (cold) neutrons
available at the NIST facility — less than 1
nanometer (billionth of a meter) — also allows the
researchers to study nanoscale magnetic properties too
small to be measured with other methods.
Work at Johns Hopkins was supported by the U.S.
Department of Energy. The project was funded by
Grants-in-Aid for Scientific Research from the Japan
Society for the Promotion of Science and for the 21st
Century Center of Excellence "Center for Diversity and
Universality in Physics'' from MEXT of Japan, and by the
Inamori Foundation. Work at NIST was supported in part by
the National Science Foundation.