Orthogonal magnetization and symmetry breaking in pyrochlore iridate Eu2Ir2O7

• Published in: Nature physics Vol. 13; no. 6; pp. 599 - 603
• Main Authors: Liang, Tian, Hsieh, Timothy H., Ishikawa, Jun J., Nakatsuji, Satoru, Fu, Liang, Ong, N. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.02.2017; Nature Publishing Group; Nature Publishing Group (NPG)
• Subjects: 639/301/119/997; 639/766/119/997; Atomic; Classical and Continuum Physics; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Complex Systems; Condensed Matter Physics; Cooling; Magnetic fields; MATERIALS SCIENCE; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Symmetry; Theoretical; California; United States > US; Massachusetts; Japan
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys4051

Electrons in the pyrochlore iridates experience a large interaction energy in addition to a strong spin–orbit interaction. Both features make the iridates promising for realizing novel states such as the topological Mott insulator. The pyrochlore iridate Eu 2 Ir 2 O 7 shows a metal–insulator transition at T N ∼ 120 K below which a magnetically ordered state develops. Using torque magnetometry, we uncover an unusual magnetic response. A magnetic field H applied in its a – b plane produces a nonlinear magnetization M ⊥ orthogonal to the plane. M ⊥ displays a d -wave field-angle pattern consistent with octupolar order, with a handedness dictated by field cooling, leading to symmetry breaking of the chirality ω . A surprise is that the lobe orientation of the d -wave pattern is sensitive to the direction of the field when the sample is field-cooled below T N , suggestive of an additional order parameter η already present at 300 K. A torque magnetometry study of the pyrochlore iridate Eu 2 Ir 2 O 7 reveals an unusual symmetry-breaking effect that persists above the Néel temperature of this antiferromagnet.