English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In positive muon spin rotation and relaxation ($\mu^+$SR) spectroscopy,positive muons ($\mu^+$) implanted into solid oxides are conventionally treatedas immobile spin-probes at interstitial sites below room temperature. This isbecause each $\mu^+$ is thought to be tightly bound to an oxygen atom in thehost lattice to form a muonic analogue of the hydroxy group. On the basis ofthis concept, anomalies in $\mu^+$SR spectra observed in oxides have beenattributed in most cases to the intrinsic properties of host materials. On theother hand, global $\mu^+$ diffusion with an activation energy of $\sim$0.1~eVhas been reported in some chemically-substituted perovskite oxides at cryogenictemperatures, although the reason for the small activation energy despite theformation of the strong O$\mu$ bond has not yet been quantitatively understood.In this study, we investigated interstitial $\mu^+$ diffusion in the perovskiteoxide lattice using KTaO$_3$ cubic perovskite as a model system. We used the$\mu^+$SR method and density functional theory calculations along with theharmonic transition state theory to study this phenomenon both experimentallyand theoretically. Experimental activation energies for global $\mu^+$diffusion obtained below room temperature were less than a quarter of thecalculated classical potential barrier height for a bottleneck $\mu^+$ transferpath. The reduction in the effective barrier height could be explained by theharmonic transition state theory with a zero-point energy correction; asignificant difference in zero-point energies for $\mu^+$ at the positions inthe O$\mu$ bonding equilibrium state and a bond-breaking transition state wasthe primary cause of the reduction. This suggests that the assumption ofimmobile $\mu^+$ in solid oxides is not always satisfied since such asignificant decrease in diffusion barrier height can also occur in otheroxides.

Understanding muon diffusion in perovskite oxides below room temperature based on harmonic transition state theory