Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Neutrons reveal unexpected magnetism in rare-earth alloy

14.06.2016

A new study by a multi-institutional team, led by researchers from Brookhaven National Laboratory and Stony Brook University, has revealed exotic magnetic properties in a rare-earth based intermetallic compound. Similar studies suggest a better understanding of those types of behaviors could lead to applications in quantum computing and improved storage device technologies.

Researchers at the Department of Energy's Oak Ridge National Laboratory and their collaborators used neutron scattering to uncover magnetic excitations in the metallic compound ytterbium-platinum-lead (Yb2Pt2Pb). Surprisingly, this three-dimensional material exhibits magnetic properties that one would conventionally expect if the connectivity between magnetic ions was only one-dimensional. Their research is discussed in a paper published in the journal Science.


This illustration shows the one-dimensional Yb ion chain in the quantum magnet Yb2Pt2Pb. The Yb orbitals are depicted as the iso-surfaces, and the green arrows indicate the antiferromagnetically aligned Yb magnetic moments. The particular overlap of the orbitals allows the Yb moments to hop between the nearest and next nearest neighbors along the chain direction, resulting in the two and four spinon excitations.

Credit: ORNL/Genevieve Martin

An electron can theoretically be understood as a bound state of three quasiparticles, which collectively carry its identity: spin, charge and orbit. It has been known that the spinon, the entity that carries information about electron spin, can "separate" itself from the others under certain conditions in one-dimensional chains of magnetic ions such as copper (Cu2+) in an insulating host. Now, the new study reveals that spinons are also present in metallic Yb2Pt2Pb.

The experimental team included ORNL postdoctoral researcher and lead author Liusuo Wu, Georg Ehlers, and Andrey Podlesnyak, instrument scientists at ORNL's Spallation Neutron Source (SNS), a DOE Office of Science User Facility. The team made use of the neutrons' sensitivity to magnetic fluctuations at the atomic scale and the world-leading capabilities of the SNS Cold Neutron Chopper Spectrometer (CNCS) instrument.

Placing a sample of Yb2Pt2Pb in the neutron beam and carefully mapping the dependence of the scattering intensity on angle and time-of-flight revealed characteristic signatures of the magnetic collective excitations in the material.

"An electron's ability to exhibit quantum magnetic behavior like this depends on how many pairings it can make with its nearest neighbors," Wu said. "In a one-dimensional chain, each has only two neighbors, making quantum fluctuations much more dramatic."

With contributions from collaborators at Brookhaven, Stony Brook University, and the University of Amsterdam, the research team developed a picture of spinons propagating in a particular direction, and how a magnetic excitation spectrum was calculated, based on that model, and compared it to the experimental data.

"The element ytterbium, found in the 4f group of the periodic table, often makes an interesting ingredient in a material. Here, the leading magnetic interactions conspire with the crystal structure and the local anisotropy to create an effect we call geometric frustration," Ehlers said. "In materials research, this gives us a handle on the properties of a particular system and allows one, ultimately, to design materials with specific desirable properties."

As in electrons, the magnetic moments in neutrons originate from their spin-1/2, the smallest possible magnetic moment in an ion or electron shell. Combined with their high penetrating power--due to the fact they carry no charge--neutrons are an ideal probe to explore magnetism in atomic systems. Here, the interesting phenomena occur at low energies and low temperatures, which is why the cold neutrons at CNCS are well suited to study them.

"At higher temperatures, the thermal effects will blur what we're able to see, because the ions start moving about more if the material is warmer, hindering our ability to see the excitations clearly," Ehlers said.

Another advantage to the CNCS instrument is that it can detect neutron scattering patterns in all three spatial dimensions simultaneously, which, according to Ehlers, proved to be crucial in the team's investigation.

"At first we were really puzzled by our results," Wu said. "But once we started to understand and look at it from the right perspective, we could see how the electrons hop between overlapping orbitals on nearest Yb neighbors.

"Now that we have a better understanding of how this happens, we can search for other materials that demonstrate similar properties, which will hopefully lead to even bigger discoveries and better technologies."

###

Co-authors of the paper, titled "Orbital-Exchange and Fractional Quantum Number Excitations in an f-electron Metal, Yb2Pt2Pb" include lead author Liusuo Wu, William Gannon, Michael Brockmann, Jean-Sebastien Caux, Moosung Kim, Yiming Qiu, John R. Copley, Georg Ehlers, Andrey Podlesnyak, Alexei Tsvelik, Igor Zaliznyak, and Meigan Aronson.

Additional contributions and complementary measurements were obtained from DOE's Brookhaven National Laboratory, the National Institute of Standards and Technology, Stony Brook University, and the University of Amsterdam.

The research conducted at ORNL's Spallation Neutron Source was supported by DOE's Office of Science. The paper is available at http://science.sciencemag.org/content/352/6290/1206.

UT-Battelle manages ORNL for the DOE's Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.

Media Contact

Jeremy Rumsey
rumseyjp@ornl.gov
865-576-2038

 @ORNL

http://www.ornl.gov 

Jeremy Rumsey | EurekAlert!

More articles from Materials Sciences:

nachricht New biomaterial could replace plastic laminates, greatly reduce pollution
21.09.2017 | Penn State

nachricht Stopping problem ice -- by cracking it
21.09.2017 | Norwegian University of Science and Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>