Strength of microscopic magnetic interactions for emergent phenomena measured

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When the magnetic interactions between nearest (blue arrows) and next-­‐nearest (purple arrow) neighbor atoms have antiparallel alignment of the respective magnetic moments, the resulting magnetic order is frustrated, because the magnetic moment (denoted in red) cannot satisfy both requirements simultaneously. This scenario is observed in the cerium-­‐based material CeRhIn5

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Microscopic magnetic interactions are at the origin of various emergent phenomena such as superconductivity, magnetic frustration, ferromagnetism and magneto-electric coupling that are important for current and future applications ranging from computing to alternative energies to transportation. To understand these phenomena, scientists work on quantifying and ultimately tuning magnetic interactions. A family of cerium (Ce)-based materials that can be tuned to exhibit superconductivity and complex magnetism has served as a test bed to study such emergent phenomena since their discovery at Los Alamos in 2000. By combining neutron spectroscopy and theory, researchers from Los Alamos National Laboratory and Oak Ridge National Laboratory’s Spallation Neutron Source have uncovered the strength of the magnetic interactions in these materials for the first time. Physical Review Letters published the findings.

Microscopic magnetic interactions are the forces between neighboring magnetic moments—that is, microscopic “compass needles” that sit on every atom in a magnetic material. Scientists have shown for the first time that the magnetic interactions in the material CeRhIn5that is part of this family are “frustrated,” because the constraints resulting from magnetic forces on the nearest and next-nearest magnetic moments cannot be fulfilled at the same time. Because researchers believe that magnetic interactions in this family of cerium materials could play an important role for the emergence of superconductivity, this result provides new insight into the complex interplay between frustrated magnetism and superconductivity.

Reference: “Magnitude of the Magnetic Exchange Interaction in the Heavy-Fermion Antiferromagnet CeRhIn5,” Physical Review Letters 113, 246403 (2014); doi: 10.1103/PhysRevLett.113.246403. Authors include Pinaki Das, Nirmal J. Ghimire, Filip Ronning, Eric D. Bauer, Joe D. Thompson, and Marc Janoschek (Condensed Matter and Magnet Science, MPA-CMMS); Shizeng Lin and Cristian D. Batista (Physics of Condensed Matter and Complex Systems, T-4); Kevin Huang (University of California, San Diego and MPA-CMMS); and Georg Ehlers (Oak Ridge National Laboratory)

The DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering and the Laboratory Directed Research and Development (LDRD) program sponsored different aspects of the LANL work. A Seaborg Institute Research Fellowship funded Huang. This effort to understand emergent phenomena in functional materials aligns with grand challenges outlined by the DOE Basic Energy Sciences and the Lab’s Materials Strategy. The research supports the Lab’s Energy Security mission area and Materials for the Future science pillar.

Technical contact: Marc Janoschek