Phase Diagram of URu2–xFexSi2 in High Magnetic Fields

Published June 27, 2018

Left: Three-dimensional phase diagram for URu2−x FexSi2 single crystals, with temperature T. Right: Normalized critical-field H/H0

Scientists used high magnetic fields and low temperatures to study crystals of URu_2–xFe_xSi₂. Using these conditions, they explored an intriguing state of matter called the "hidden order phase" that exhibits emergent behavior. Emergent behavior occurs when the whole is greater than the sum of its parts, meaning the whole has exciting properties that its parts do not possess; it is an important concept in philosophy, the brain and theories of life. This data provide strict constraints on theories of emergent behavior.

What did scientists discover?

MagLab users measured the resistance of single crystals of URu_2–xFe_xSi₂ for various iron (Fe) concentrations, x, in very high magnetic fields. Changes in the electrical resistance allowed the boundaries between different phases of this material system to be mapped.

Why is this important?

In philosophy, systems theory, science and art, emergence occurs when the whole is greater than the sum of the parts, meaning the whole has properties that its parts do not possess. These properties come about because of interactions among the parts. Emergence plays an increasing role in theories of complex materials. The mysterious hidden order phase of URu₂Si₂ is a prime example of emergence, and this experiment allowed us to map out a three-dimensional (3D) field-temperature-composition phase diagram for the first time in this compound. This work established a single relation between the transition temperature and the critical magnetic field for the hidden order (HO) phase, which imposes constraints on any theories of the HO phase and its emergent behavior.

Who did the research?

Sheng Ran^a,b, Inho Jeon^b,c, Naveen Pouse^a,b, Alexander J. Breindel^a,b, Noravee Kanchanavatee^a,b, Kevin Huang^b,c, Andrew Gallagher^d, Kuan-Wen Chen^d, David Graf^d, Ryan E. Baumbach^d, John Singleton^d, and M. Brian Maple^a,b,c.

^aPhysics, UCSD; ^bCenter for Advanced Nanoscience, UCSD; ^cMaterials Science and Engineering, UCSD; ^dNational MagLab

Why did they need the MagLab?

Very high magnetic fields and cryogenic temperatures are required to access the exotic phases that exhibit emergent behavior. Special instrumentation, unique to the MagLab, was used to make sufficiently precise resistance measurements.

Details for scientists

View or download the expert-level Science Highlight, Phase diagram of URu_2–xFe_xSi₂ in high magnetic fields
Read the full-length publication, Phase diagram of URu_2–xFe_xSi₂ in high magnetic fields, in PNAS

Funding

This research was funded by the following grants: A. Gallagher, K.-W. Chen, D. Graf, R.E. Baumbach, J. Singleton (NSF DMR-1157490); N.P. Wilson, X.Xu S. Ran, I. Jeon, N. Pouse, A.J. Breindel, N. Kanchanavatee, K. Huang, M.B. Maple (DOE DE-FG02-04ER46105 and DE-NA0002909, NSF DMR-1206553)

For more information, contact Marcelo Jaime.