1. Ramification of complex magnetism in Nd$_2$Ir$_2$O$_7$ observed by Raman scattering spectroscopy
- Author
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Xu, Yuanyuan, Yang, Yang, Teyssier, Jérémie, Ohtsuki, Takumi, Qiu, Yang, Nakatsuji, Satoru, van der Marel, Dirk, Perkins, Natalia, and Drichko, Natalia
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences - Abstract
Using Raman scattering spectroscopy, we uncover a complex magnetic behavior of \nio, which stands out among magnetic pyrochlores by the lowest temperature of the all-in-all-out (AIAO) Ir moments ordering ($T^\mathrm{N}_{\small\rm{Ir}}=33$~K) and the highest temperature at which AIAO order of rare-earth Nd ions is detected ($T^\mathrm{*}_{\small\rm{Nd}}$=14~K). Our work suggests that in the temperature range between 14~K and 33~K, Nd magnetic moments exhibit characteristic spin ice fluctuations, which indicate a strong enhancement of magnetic interactions between Nd ions. 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. 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 of a broad mode at 14 meV, characteristic of the spinon continuum originated from Nd spin ice fluctuations. While two one-magnon excitations show minimal temperature evolution with decreasing temperature, the 14 meV mode shifts to higher frequencies as the temperature approaches a crossover to Nd AIAO order, broadens and disappears below 14~K. An additional two-magnon excitation of the AIAO Nd order at around 33 meV appears in the spectra at low temperatures.
- Published
- 2023
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