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SUMMARY:Data analysis for µSR experiments with negative muons.
DTSTART;VALUE=DATE-TIME:20220828T123000Z
DTEND;VALUE=DATE-TIME:20220828T124500Z
DTSTAMP;VALUE=DATE-TIME:20220826T104856Z
UID:indico-contribution-3675@indico.stfc.ac.uk
DESCRIPTION:Speakers: George Gill (University of Oxford / ISIS)\nNegative 
 muons are often overlooked compared to their positive counterpart\, partly
  due to the loss of around  $\\frac{5}{6}$ of the $\\mu^{-}$ spin polarisa
 tion when a $\\mu^{-}$ cascades down to the 1s muonic ground state after b
 eing captured by a nucleus. One needs to count for around 36 times as long
  to get statistics comparable to that of a $\\mu^{+}$SR experiment. Howeve
 r\, there has been a recent revival of $\\mu^{-}$SR experiments\, particul
 arly in the study of hydrogen storage and battery materials [1\,2]. When s
 topped in a material of atomic number  $Z$\, $\\mu^{-}$ forms a muonic ato
 m and cascades down to its ground state. The muon Bohr radius is 200 times
  smaller than the electron Bohr radius\, and so this probe behaves like an
  ultra-dilute atom of apparent nuclear charge $Z-1$. The $\\mu^{-}$ will b
 e strongly hyperfine coupled to the nuclear spin of the capture atom\, but
  if that nuclear spin is zero\, such as an oxygen in MnO\, the only coupli
 ng will be to the nuclear dipolar fields in a region very close to that ca
 pture nucleus. Because of these difficulties new analysis techniques have 
 been developed in WiMDA [3] for the fitting of $\\mu^{-}$SR data\, and we 
 have adapted the DFT+$\\mu^{+}$ technique for the case of a negative muon.
  Both of these new techniques have been applied to MnO where the dipole fi
 eld simulations show a large field at the oxygen site\, and DFT+$\\mu^{-}$
  calculations show a Jahn-Teller-like distortion around the negative muon.
 \n\nReferences\n[1] J.Sugiyama *et al* Phys. Rev. Lett. 121\, 087202 (2018
 ).\n[2] J. Sugiyama *et al*\, Phys. Rev. Res. 2\, 033161 (2020).\n[3] F.L.
  Pratt\, Physica B 289-290\, 710 (2000)\n\nhttps://indico.stfc.ac.uk/event
 /53/contributions/3675/
LOCATION: Aula dei Cavalieri\, University Central Palace\, via Università
  12
URL:https://indico.stfc.ac.uk/event/53/contributions/3675/
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