Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu${}_{2}$Ir${}_{2}$O${}_{7}$

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Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu $_{2}$ Ir $_{2}$ O $_{7}$

Songrui Zhao, J. M. Mackie, D. E. MacLaughlin, O. O. Bernal, J. J. Ishikawa, Y. Ohta, and S. Nakatsuji

Phys. Rev. B 83, 180402(R) – Published 2 May 2011

Abstract

Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu $_{2}$ Ir $_{2}$ O $_{7}$ yield a well-defined muon spin precession frequency below the metal-insulator/antiferromagnetic transition temperature $T_{M} = 120$ 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 $~ T_{M}$ 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 iridates BaIrO $_{3}$ and Sr $_{2}$ Ir $_{2}$ O $_{4}$ . Eu $_{2}$ Ir $_{2}$ O $_{7}$ may be only weakly frustrated; if so, the singularity might be associated with the small-gap insulating state rather than frustration.

Received 15 March 2011

DOI:https://doi.org/10.1103/PhysRevB.83.180402

Authors & Affiliations

Songrui Zhao^1,*, J. M. Mackie¹, D. E. MacLaughlin¹, O. O. Bernal², J. J. Ishikawa³, Y. Ohta³, and S. Nakatsuji³

¹Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
²Department of Physics and Astronomy, California State University, Los Angeles, California 90032, USA
³Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan

^*Present address: Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec, Canada H3A 2A7.

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Vol. 83, Iss. 18 — 1 May 2011

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