Search

We report on a study of the motional characteristics of positively charged muonium defect centers in In2O3 powder. Zero field muon spin relaxation (ZF-MuSR) measurements were taken from 2 K to 950 K. Results show the positively charged muonium defects occupying two states (Mu1 and Mu2) at low temperatures while a third state (Mu3) is introduced as the temperature is increased. Mu1 is occupied more heavily than Mu2 at low temperatures by a ratio of ~8:1. The Mu1 state changes to the Mu2 state starting at 300 K with site change energy of 0.46±0.11 eV and is essentially not occupied above 500 K. The Mu2state becomes diffusively mobile with a barrier of 0.78±0.07 eV at 350 K and begins trapping at Mu3 at 400 K with a capture energy of 0.56±0.019 eV. A metastable region is observed between 500 K and 650 K in which the ratio between Mu2 and Mu3 amplitudes and the hop rate of Mu2 are both roughly constant, implying a steady state trap and release balance between mobile Mu2 centers and the Mu3 trap state. Above 650 K, the muonium defects release from the Mu3 trap to the Mu2 diffusive state with a dissociation energy of 0.901±0.003 eV. The upper limit on the high temperature diffusion barrier is determined, from the Mu2 hop rate, to be 0.43±0.03 eV. [ABSTRACT FROM AUTHOR]

We report on a study of the motional characteristics of positively charged muonium defect centers in In2O3 powder. Zero field muon spin relaxation (ZF-MuSR) measurements were taken from 2 K to 950 K. Results show the positively charged muonium defects occupying two states (Mu1 and Mu2) at low temperatures while a third state (Mu3) is introduced as the temperature is increased. Mu1 is occupied more heavily than Mu2 at low temperatures by a ratio of ~8:1. The Mu1 state changes to the Mu2 state starting at 300 K with site change energy of 0.46±0.11 eV and is essentially not occupied above 500 K. The Mu2state becomes diffusively mobile with a barrier of 0.78±0.07 eV at 350 K and begins trapping at Mu3 at 400 K with a capture energy of 0.56±0.019 eV. A metastable region is observed between 500 K and 650 K in which the ratio between Mu2 and Mu3 amplitudes and the hop rate of Mu2 are both roughly constant, implying a steady state trap and release balance between mobile Mu2 centers and the Mu3 trap state. Above 650 K, the muonium defects release from the Mu3 trap to the Mu2 diffusive state with a dissociation energy of 0.901±0.003 eV. The upper limit on the high temperature diffusion barrier is determined, from the Mu2 hop rate, to be 0.43±0.03 eV. [ABSTRACT FROM AUTHOR]

We report on our measurements of local and bulk magnetic features in weakly Mn doped ZnGeP2. Utilizing muon spin rotation and relaxation measurements, we identify local ferromagnetic order and fluctuations in the local fields as sampled by an implanted muon (μ+). We also report on field induced ferromagnetism occurring above the claimed paramagnetic to ferromagnetic transition temperature (Tc = 312 K) [ABSTRACT FROM AUTHOR]

We use the longitudinal field muon spin relaxation technique to observe charge-state and site-change transitions of muonium in Si1-xGex alloys. In this project, we examine the temperature and magnetic field dependences of the relaxation rates for Si1-xGex samples (x = 0.77, 0.81, and 0.84), in the composition range where the acceptor level lies within the band gap. This study particularly focuses on the relaxation rates for Si0.19Ge0.81 to identify various cyclic charge-state and site-change processes as a function of both temperature and magnetic field. We extract the paramagnetic hyperfine constant and the relevant transition rate parameters for site changes and charge-state transitions involving Mu acceptor states for this sample. At small x, a site change dominates the transition out of the neutral T-site acceptor state, while in higher Ge content alloys hole ionization becomes the dominant transition out of the MuT0. [ABSTRACT FROM AUTHOR]

Muon spin relaxation measurements in the III–V nitrides have provided data on the motion of each of the three charge-states of the muonium ‘isotope’ of hydrogen. Motional parameters are established for Mu+ in InN, Mu0 in AlN, and Mu- in GaN, with qualitative results in the other materials. Both Mu+ and Mu0 show tunneling below 300 K and thermal diffusion at higher temperatures leading to interactions with other impurities or extended defects. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report on our measurements of local and bulk magnetic features in weakly Mn doped ZnGeP2. Utilizing muon spin rotation and relaxation measurements, we identify local ferromagnetic order and fluctuations in the local fields as sampled by an implanted muon (μ+). We also report on field induced ferromagnetism occurring above the claimed paramagnetic to ferromagnetic transition temperature (Tc = 312 K) [ABSTRACT FROM AUTHOR]