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arXiv · 1110.6605

Emergence of magnetic long-range order in frustrated pyrochlore Nd$_2$Ir$_2$O$_7$ with metal-insulator transition

K. Tomiyasu·K. Matsuhira·K. Iwasa·M. Watahiki·S. Takagi·M. Wakeshima·Y. Hinatsu·M. Yokoyama·K. Ohoyama·K. Yamada
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Abstract

In this study, we performed powder neutron diffraction and inelastic scattering measurements of frustrated pyrochlore Nd$_2$Ir$_2$O$_7$, which exhibits a metal-insulator transition at a temperature $T_{\rm MI}$ of 33 K. The diffraction measurements revealed that the pyrochlore has an antiferromagnetic long-range structure with propagation vector $\vec{q}_{0}$ of (0,0,0) and that it grows with decreasing temperature below 15 K. This structure was analyzed to be of the all-in all-out type, consisting of highly anisotropic Nd$^{3+}$ magnetic moments of magnitude $2.3\pm0.4$$μ_{\rm B}$, where $μ_{\rm B}$ is the Bohr magneton. The inelastic scattering measurements revealed that the Kramers ground doublet of Nd$^{3+}$ splits below $T_{\rm MI}$. This suggests the appearance of a static internal magnetic field at the Nd sites, which probably originates from a magnetic order consisting of Ir$^{4+}$ magnetic moments. Here, we discuss a magnetic structure model for the Ir order and the relation of the order to the metal-insulator transition in terms of frustration.

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K. Tomiyasu, K. Matsuhira, K. Iwasa, M. Watahiki, S. Takagi, M. Wakeshima, Y. Hinatsu, M. Yokoyama, K. Ohoyama, K. Yamada. 2012-01-03. Emergence of magnetic long-range order in frustrated pyrochlore Nd$_2$Ir$_2$O$_7$ with metal-insulator transition. https://doi.org/10.1143/jpsj.81.034709

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