Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu2Ir2O7 yield a well-defined muon spin precession frequency below the metal-insulator/antiferromagnetic transition temperature TM = 120 K, indicative of long-range commensurate magnetic order and thus ruling out quantum spin liquid and spin-glass-like ground states. The dynamic muon spin relaxation rate is temperature-independent between 2 K and ~TM and yields an anomalously long Ir^{4+} spin correlation time, suggesting a singular density of low-lying spin excitations. Similar behavior is found in other pyrochlores and geometrically frustrated systems, but also in the unfrustrated iridate BaIrO3. Eu2Ir2O7 may be only weakly frustrated; if so, the singularity might be associated with the small-gap insulating state rather than frustration.
@article{arxiv.1104.1213,
title = {Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O7},
author = {Songrui Zhao. J. M. Mackie and D. E. MacLaughlin and O. O. Bernal and J. J. Ishikawa and Y. Ohta and S. Nakatsuji},
journal= {arXiv preprint arXiv:1104.1213},
year = {2015}
}
Comments
5 pages, 3 figures, to be published in Physical Review B (Rapid Communications)