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SUMMARY:Negative muon spin rotation and relaxation study on antiferromagne
 tic order of Na clusters in sodalite
DTSTART;VALUE=DATE-TIME:20220830T164000Z
DTEND;VALUE=DATE-TIME:20220830T170000Z
DTSTAMP;VALUE=DATE-TIME:20220826T120854Z
UID:indico-contribution-3804@indico.stfc.ac.uk
DESCRIPTION:Speakers: Takehito Nakano (Ibaraki University)\n$\\mu^+$SR is 
 used in various research fields as a sensitive local magnetic probe. Altho
 ugh the implanted $\\mu^+$ stop at interstitial sites in the crystal\, it 
 is often difficult to determine the sites precisely. On the other hand\, t
 he implanted $\\mu^-$ are captured by nuclei and have different lifetimes 
 for each nuclide. Thus\, the $\\mu^-$ position is unambiguously determined
  by measuring the lifetime. However\, the spin polarization of $\\mu^-$ is
  reduced down to about 1/6 during the capture process\, requiring much hig
 her statistics than $\\mu^+$SR. Recent improvements in the beam intensity 
 and detection efficiency of pulsed-muon facilities have made $\\mu^-$SR ex
 periments feasible\, and such an advanced $\\mu^-$SR is used to study ion 
 dynamics in solids.$^1$ We here report an attempt to investigate magnetic 
 materials with the advanced $\\mu^-$SR.\nNa$_4^{3+}$ clusters can be arran
 ged in a bcc structure in sodalite crystal. Antiferromagnetic ordering occ
 urs below $T_N =$ 50 K due to the exchange interaction between the s-elect
 rons in the arrayed clusters. In ZF-$\\mu^+$SR\, a homogeneous local field
  of 92 Oe is observed at low temperatures.$^2$ Our recent study shows it
 ’s due to the Fermi contact at the cage center. In the present $\\mu^-$S
 R\, the lifetime analysis shows the signal at the oxygen site is dominant.
  The initial asymmetry of the time spectra dropped sharply below $T_N$\, b
 ut muon spin precession due to a homogeneous local field couldn’t be obs
 erved. The decoupling by longitudinal field shows the local field of about
  0.4 kOe. This value can be explained as the local field of oxygen sites w
 hen the spatial distribution of s-electron wave function is approximately 
 incorporated. These results demonstrate the importance to study the magnet
 ic nature of materials with $\\mu^{\\pm}$SR.\n$^1$I. Umegaki *et al*.\, J.
  Phys. Chem. C **126**\, 10506 (2022).\n$^2$R. Scheuermann *et al*.\, Phys
 . Rev. B **66**\, 144429 (2002).\n\nhttps://indico.stfc.ac.uk/event/53/con
 tributions/3804/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3804/
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