Electrons in the pyrochore 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 Eu2Ir2O7 shows a metal-insulator transition at TN∼ 120 K below which a magnetically ordered state develops. Using torque magnetometry, we uncover a highly 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 TN, suggestive of an additional order parameter η already present at 300 K.
@article{arxiv.1603.08022,
title = {Orthogonal Magnetization and Symmetry Breaking in Pyrochlore Iridate Eu2Ir2O7},
author = {Tian Liang and Timothy H. Hsieh and Jun J. Ishikawa and Satoru Nakatsuji and Liang Fu and N. P. Ong},
journal= {arXiv preprint arXiv:1603.08022},
year = {2017}
}