Mössbauer spectroscopy vs
μSR
Julia ChangPHYS 590B
Spring, 2019
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Mechanism
Mössbauer spectroscopy μSR
What do we use? γ rays 100% polarized muon beam
What do we measure?
numbers of γ-ray photons pass through specimen as a function
of γ-ray energy
Numbers of positrons(polarization of muons) as a
function of timeWhat could we get? Local chemical environment due
to hyperfine interactions:isomer shift(IS), electric
quadrupole splitting (EQS),hyperfine magnetic filed
(HMF)
Magnetic field inside matter at a microscopic
level
What is cool? Recoil-free emission:momentum sharing and no
phonon excitation
Precession of muon due to local magnetic field
P. Dalmas de Réotier. Introduction to muon spin rotation and relaxation(μSR). Brent Fultz, “Mössbauer Spectrometry”, in Characterization of Materials. Elton Kaufmann, Editor(John Wiley, New York, 2011). 2
Instrument
Mössbauer spectrometerμSR
P. Dalmas de Réotier. Introduction to muon spin rotation and relaxation(μSR). Brent Fultz, “Mössbauer Spectrometry”, in Characterization of Materials. Elton Kaufmann, Editor(John Wiley, New York, 2011).
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Experimental example 1. Spin-glass
Spin glass: frozen disordered magnetic spin
Local spin
Mössbauer spectroscopy: Freezing T
μSR: Dynamics
Binder, Kurt, and A. Peter Young. Reviews of Modern physics 58, no. 4 (1986): 801
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16.8 at.% Fe-Au
paramagneticelectric quadrupole splitting
ferromagneticmagnetic hyperfine splitting
Hext=0Hext=20 kOe
spin aligned to Hext
frozen spintransverse to Hext
J. Lauer and W. KeunePhys. Rev. Lett. 48, 1850 (1982)
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Kubo-Toyabe function : static zero-field relaxation function of random field with Gaussian distribution
P. Dalmas de Réotier. Introduction to muon spin rotation and relaxation(μSR). 6
1 at.% Fe-Au
static field
νa
decay rate
Zero field spin-relaxation function calculation for μ+ in dilute random moments
Uemura, Y. J. Phys. Rev. Lett. 45 (1980): 583 7
Dynamic field
𝜏𝜏𝑐𝑐 =1ν
8P. Dalmas de Réotier. Introduction to muon spin rotation and relaxation(μSR).
Experimental example 2. Superconductor-LE μSR
Suter, A., et al. Physical review letters 92.8 (2004): 087001
λ𝐿𝐿 = 18𝑛𝑛𝑛𝑛ξ0 = 1600𝑛𝑛𝑛𝑛
T=3.05 KHext=8.82 mT
Pb
YBa2Cu3O75.2 keV
14.8 keV
solid curve: BCS fitdashed curve: exponential dependence 9
ISIS facility (UK)P. Dalmas de Réotier. Introduction to muon spin rotation and relaxation(μSR). https://mars.nasa.gov/mer/mission/instruments/mb/
Mössbauer Spectrometer on the Mars Exploration Rovers, Spirit and Opportunity
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http://www.particleadventure.org/index.html
Thank you. Questions?11
Extra slides
https://www.rsc.org/Membership/Networking/InterestGroups/MossbauerSpect/part2.asp
𝐼𝐼 𝑜𝑜:𝑛𝑛: 𝑖𝑖 = 3:4𝑠𝑠𝑖𝑖𝑛𝑛2𝜃𝜃
1 + 𝑐𝑐𝑜𝑜𝑠𝑠2𝜃𝜃: 1
position: splitting of energy levelintensity: angle θ between γ ray and nuclear spin moment
o m i
middle peak vanish: θ=0the external magnetic field is parallel with γ ray
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