Local Electronic Structure Of Dilute Hydrogen In Beta-Mno2

The electronic and magnetic states of beta-MnO2 in terms of hydrogen impurities have been investigated by the muon spin rotation technique combined with density-functional theory (DFT) calculations for muon as pseudohydrogen. We found that 85% of implanted muons are localized in the oxygen channels of the rutile structure and behave like interstitial protons (Mu(+)) except those (7.6%) forming a charge-neutral state (Mu(0)) at 2.3 K, which indicates that interstitial hydrogen acts like a shallow donor within less than 0.1 meV of ionization energy. The residual 15% of muons are attributed to those related to lattice imperfection as Mn vacancies. Detailed analyses combined with the DFT approach suggested that the muon is localized at the center of the oxygen channel due to its large zero-point vibration energy.