Muon-Spin-Rotation study of yttria-stabilized zirconia (ZrO2:Y): Evidence for muon and electron separate traps

13th International Conference on Muon Spin Rotation, Relaxation and Resonance

Vieira, R.B.L.^1 ; Vilão, R.C.^1 ; Gordo, P.M.^1 ; Marinopoulos, A.G.^1,2 ; Alberto, H.V.^1 ; Duarte, J. Piroto^3 ; Gil, J.M.^1 ; Weidinger, A.^1 ; Lord, J.S.^4

CEMDRX, Department of Physics, University of Coimbra, Coimbra, Portugal^1

Department of Physics, I3N, University of Aveiro, Aveiro

3810-193, Portugal^2

Institute of Shock Physics, Department of Physics, Imperial College London, Exhibition Road, London

SW7 2AZ, United Kingdom^3

ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon

OX11 0QX, United Kingdom^4

关键词: Coulomb potential;    Diamagnetic signals;    Dipolar magnetic fields;    Hyperfine interactions;    Increasing temperatures;    Longitudinal fields;    Muon spin rotation;    Unpaired electrons;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/551/1/012050/pdf
DOI  :  10.1088/1742-6596/551/1/012050

来源: IOP

【 摘 要 】

This paper is part of an extended study of oxide materials with the μSR technique. As an example, we present here experimental data on yttria-stabilized zirconia (ZrO2 doped with 8% Y2O3). Three different muon states can be distinguished: i) Deep muonium (less than 17(1)% fraction), seen as a fast-relaxing signal or indirectly via decoupling measurements in high longitudinal fields, ii) μ+in a paramagnetic environment 62(6)% fraction), characterized by a very weak but clearly-visible hyperfine interaction, and iii) diamagnetic muon 21(1)% fraction); the diamagnetic signal is broadened only by the interaction with nuclear moments. The state corresponding to μ+in a paramagnetic environment and the diamagnetic state are attributed to the same (oxygen-bound) muon configuration, but we assume that they have different electron surroundings (with or without an unpaired electron in the vicinity). The paramagnetic electron is not captured in the Coulomb potential of the positive muon but is self-trapped (polaron formation) at a nearby Zr ion. The distant electron interacts with the muon only via dipolar magnetic fields. This explains the very weak hyperfine interaction felt by the μ+state in a paramagnetic environment. A further result of the experiment is that the disappearance of this signal with increasing temperature is not due to ionization of an electron shallowly bound to the muon but is caused by rapid spin fluctuations of the electron, averaging the hyperfine interaction to zero.