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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