Revealing the Nature of Antiferroquadrupolar Ordering in Cerium Hexaboride: CeB6

• Published in: Physical review letters Vol. 122; no. 7; p. 076401
• Main Authors: Barman, C K, Singh, Prashant, Johnson, Duane D, Alam, Aftab
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 19-02-2019; American Physical Society (APS)
• Subjects: Antiferromagnetism; Cerium; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Crystal structure; Electron states; Electronic structure; Ferromagnetism; First principles; Hydrostatic pressure; MATERIALS SCIENCE; Organic chemistry; Spin-orbit interactions; X-ray scattering
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.122.076401

The cerium hexaboride (CeB6) f-electron compound displays a rich array of low-temperature magnetic phenomena, including a “magnetically hidden” order, identified as multipolar in origin via advanced x-ray scattering. From first-principles electronic-structure results, we find that the antiferroquadrupolar (AFQ) ordering in CeB6 arises from crystal-field splitting and yields a band structure in agreement with experiments. With interactions of p electrons between Ce and B6 being small, the electronic state of CeB6 is suitably described as Ce (4f1)3+ (e−)(B6)2−. The AFQ state of orbital spins is caused by an exchange interaction induced through spin-orbit interaction, which also splits the J = 5/2 state into a Γ8 ground state and a Γ7 excited state. Within the smallest antiferromagnetic (AFM) (111) configuration, an orbital-ordered AFQ state appears during charge self-consistency, and it supports the appearance of a “hidden” order. Hydrostatic pressure (either applied or chemically induced) stabilizes the AFM (AFQ) states over a ferromagnetic one, as observed at low temperatures.