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3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Nd2Ir2O7 by Materials Project

Nd2Ir2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Nd3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are two shorter (2.27 Å) and six longer (2.55 Å) Nd–O bond lengths. Ir4+ is bonded to six equivalent O2- atoms to form corner-sharing IrO6 octahedra. The corner-sharing octahedral tilt angles are 50°. All Ir–O bond lengths are 2.04 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Nd3+ and two equivalent Ir4+ atoms to form a mixture of distorted edge and corner-sharing ONd2Ir2 tetrahedra. In the second O2- site, O2- is bonded to four equivalent Nd3+ atoms to form a mixture of edge and corner-sharing ONd4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Ramification of complex magnetism in Nd 2 Ir 2 O 7 observed by Raman scattering spectroscopy

Using Raman scattering spectroscopy, we uncover a complex magnetic behavior of Nd2Ir2O7, which stands out among magnetic pyrochlores by the lowest temperature of the all-in-all-out (AIAO) Ir moments ordering (${T}_{{\rm{Ir}}}^{{\rm{N}}} = 33$ K) and the highest temperature at which AIAO order of rare-earth Nd ions is detected (${T}_{{\rm{Nd}}}^{{\rm{* }}}$ = 15 K). Detected magnetic Raman scattering and calculations of expected response allow us to demonstrate that the ordering of Ir magnetic moments is accompanied by an appearance of one-magnon Raman modes at 26.3 and 29.6 meV compatible with the AIAO order and allowing to estimate the energies of Ir-Ir interactions. An additional two-magnon excitation of the AIAO Nd order at around 33 meV appears in the spectra below the ordering temperature of Nd moments ${T}_{{\rm{Nd}}}^{{\rm{* }}}$ = 15 K. In the temperature range between 15 K and 33 K we observe a broad mode, which demonstrates strong temperature dependence and shifts on cooling below 20 K from 14 meV to higher frequencies, and disappears at 5 K, when two-magnon excitation of Nd moments becomes prominent. We suggest an interpretation of this excitation in terms of continuum arising from collective fluctuations of Nd moments above the transition. This complex behavior emerges from the interplay of strong spin-orbit coupling, electronic correlations, and geometric frustration on two magnetic pyrochlore sublattices of Nd and Ir ions.

magnetic properties and materials↗