Material May Demonstrate Long-Sought 'Liquid' Magnetic State

Sep 08, 2005
Material May Demonstrate Long-Sought 'Liquid' Magnetic State

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 research published in the Sept. 9 issue of Science.

Image: A crystal diagram shows the triangle-shaped atomic structure of nickel gallium sulfide, which may have an unusual magnetic "liquid" state at low temperatures. Red spheres represent nickel, green spheres are gallium, and yellow are sulfur. Credit: S. Nakatsuji et al., Science, 9/9/2005

The material, nickel gallium sulfide (NiGa2S4), was synthesized by scientists at Kyoto University. Its properties were studied by both the Japanese team and by researchers from The Johns Hopkins University 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 Gaithersburg, Md.

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, fluid-like 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 Collin Broholm, a professor in the Department of Physics and Astronomy in Johns Hopkins' Krieger School of Arts and Sciences, "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," says Broholm, "but the triangular crystal structure prevents this from happening in this material."

The team conducted its neutron experiments with an instrument called a "disk chopper spectrometer." The only one 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," said Yiming Qiu, a NIST guest researcher from the University of Maryland.

Multi-colored arrows show the disordered array of magnetic spins ...

Image: Multi-colored arrows show the disordered array of magnetic spins of electrons within nickel gallium sulfide. The data were collected by precisely measuring the timing and change in direction of neutrons as they were passed through the material. Credit: S. Nakatsuji et al., Science, 9/9/2005

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.

S. Nakatsuji, Y. Nambu, H. Tonomura, O. Sakai, S. Jonas, C. Broholm, H. Tsunetsugu, Y. Qiu, Y. Maeno. "Spin Disorder on a triangular lattice." Science, Sept. 9, 2005.

Source: Johns Hopkins University

Explore further: Controlling core switching in Pac-man disks

add to favorites email to friend print save as pdf

Related Stories

How electrons split: New evidence of exotic behaviors

Dec 15, 2014

Electrons may be seen as small magnets that also carry a negative electrical charge. On a fundamental level, these two properties are indivisible. However, in certain materials where the electrons are constrained in a quasi ...

Atomic trigger shatters mystery of how glass deforms

Oct 18, 2014

Throw a rock through a window made of silica glass, and the brittle, insulating oxide pane shatters. But whack a golf ball with a club made of metallic glass—a resilient conductor that looks like metal—and the glass not ...

How cloud chambers revealed subatomic particles

Sep 23, 2014

Atoms are made of electrons, protons and neutrons. Protons and neutrons are in turn made up of quarks. These are just some of the elementary particles that make up the foundation of modern particle physics. ...

Recommended for you

Finding faster-than-light particles by weighing them

20 hours ago

In a new paper accepted by the journal Astroparticle Physics, Robert Ehrlich, a recently retired physicist from George Mason University, claims that the neutrino is very likely a tachyon or faster-than-light par ...

Controlling core switching in Pac-man disks

Dec 24, 2014

Magnetic vortices in thin films can encode information in the perpendicular magnetization pointing up or down relative to the vortex core. These binary states could be useful for non-volatile data storage ...

World's most complex crystal simulated

Dec 24, 2014

The most complicated crystal structure ever produced in a computer simulation has been achieved by researchers at the University of Michigan. They say the findings help demonstrate how complexity can emerge ...

Atoms queue up for quantum computer networks

Dec 24, 2014

In order to develop future quantum computer networks, it is necessary to hold a known number of atoms and read them without them disappearing. To do this, researchers from the Niels Bohr Institute have developed ...

New video supports radiation dosimetry audits

Dec 23, 2014

The National Physical Laboratory (NPL), working with the National Radiotherapy Trials Quality Assurance Group, has produced a video guide to support physicists participating in radiation dosimetry audits.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.