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Report No.

Large trigonal-field effect on spin-orbit coupled states in a pyrochlore iridate

Uematsu, Daisuke*; Sagayama, Hajime*; Arima, Takahisa*; Ishikawa, Jun*; Nakatsuji, Satoru*; Takagi, Hidenori*; Yoshida, Masahiro*; Mizuki, Junichiro; Ishii, Kenji

The half-filled topmost valence band of Ir$$^{4+}$$ in several iridates such as Sr$$_2$$IrO$$_4$$, IrO$$_2$$, and CaIrO$$_3$$ has been proposed to originate mainly from the spin-orbit coupled $$J_{rm eff}=1/2$$ states. In pyrochlore iridates $$R_2$$Ir$$_2$$O$$_7$$ ($$R$$: rare earth), some exotic electronic states are theoretically proposed by assuming $$J_{rm eff}=1/2$$ states. However, the octahedral coordination around Ir is trigonally distorted, which may affect the energy level scheme of Ir $$5d$$ states. Here, we report spectra of resonant elastic and inelastic X-ray scattering in Eu$$_2$$Ir$$_2$$O$$_7$$ at the Ir $$L$$ edges. A large suppression of the magnetic scattering signal at the Ir $$L_{rm II}$$ edge supports the $$J_{rm eff}=1/2$$ picture rather than the $$S=1/2$$ one. The inelastic scattering spectrum indicates that the magnitude of the trigonal field on the Ir$$^{4+}$$ states is evaluated to be comparable to the spin-orbit interaction. The energy diagram of the $$5d$$ state is proposed based on the simple cluster model.



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Category:Materials Science, Multidisciplinary



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