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arXiv · 1602.06692

Cage Electron-Hydroxyl Complex State as Electron Donor in Mayenite

M. Hiraishi·K. M. Kojima·M. Miyazaki·I. Yamauchi·H. Okabe·A. Koda·R. Kadono·S. Matsuishi·H. Hosono
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Abstract

It is inferred from the chemical shift of muon spin rotation ($\mu$SR) spectra that muons implanted in pristine (fully oxidized) mayenite, [Ca$_{12}$Al$_{14}$O$_{32}]^{2+}$[$\square_5$O$^{2-}$] (C12A7, with $\square$ referring to the vacant cage), are bound to O$^{2-}$ at the cage center to form OMu$^-$ (where Mu represents muonium, a muonic analog of the H atom). However, an isolated negatively charged state (Mu$^-$, an analog of H$^-$) becomes dominant when the compound approaches the state of electride [Ca$_{12}$Al$_{14}$O$_{32}]^{2+}$[$\square_4$2e$^{-}$] as a result of the reduction process. Moreover, the OMu$^-$ state in the pristine specimen exhibits depolarization of paramagnetic origin at low temperatures (below $\sim$30~K), indicating that OMu$^-$ accompanies a loosely bound electron in the cage that can be thermally activated. This suggests that interstitial muons (and hence H) forming a "cage electron-hydroxyl" complex can serve as electron donors in C12A7.

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M. Hiraishi, K. M. Kojima, M. Miyazaki, I. Yamauchi, H. Okabe, A. Koda, R. Kadono, S. Matsuishi, H. Hosono. 2016-02-22. Cage Electron-Hydroxyl Complex State as Electron Donor in Mayenite. https://doi.org/10.1103/physrevb.93.121201

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