Spin Dynamics of Polarised Fermi-liquid 3He

Nyman, Robert Andrew (2003) Spin Dynamics of Polarised Fermi-liquid 3He. PhD thesis, University of Nottingham.

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Abstract

The spin-dynamics of Fermi-liquid helium-3 in pure form and in its

mixtures with helium-4 are considered in this thesis. A linearised

model of the spin dynamics is developed from Leggett's equation of

motion, including spin-diffusion, the Leggett-Rice spin-rotation

effect and cylindrical boundary conditions . The equations are

solved using a matrix formalism, allowing simulation of FIDs, NMR

spectra and spin-echoes. The boundary conditions are shown to

cause deviations of spin-echo amplitude and phase from the

predictions of Leggett and Rice, for realistic experiments. The

model is extended to include the demagnetising field (dipolar

field) due to the magnetisation of the sample itself. Simulations

show that, when the demagnetising field is strong, spectral

clustering is present and sharp peaks are observed in the NMR

spectrum.

Data from NMR experiments on 3He and 3He-4He mixtures in

an 11.3T magnetic field, performed in Nottingham in 1999/2000, are

analysed. The analysis of 6.2% 3He mixture is predominantly by

least-squares fitting of the model (excluding demagnetising field)

to spin-echo data, yielding the transverse spin-diffusion

coefficient and spin-rotation parameter as functions of

temperature down to 3.4mK. Parameters are seen to deviate from the

1/Ta^2 characteristic of Fermi-liquid transport parameters, with

a 1/(T^2+Ta^2) form, indicative of spin-transport anisotropy.

The anisotropy temperature scale Ta is found to be 6+-1 mK.

Analysis of pure 3He experiments is by qualitative comparison

of spectroscopic data with the model (including demagnetising

field): many observed features are reproduced by the simulation.

Item Type:Thesis (PhD)
Supervisors:Owers-Bradley, John
Bowley, Roger
Uncontrolled Keywords:ultra-low temperature, NMR, spin dynamics, spin diffusion, Leggett-Rice effect, Helium-3, 3He, Helium mixtures, Fermi liquid
Faculties/Schools:UK Campuses > Faculty of Science > School of Physics and Astronomy
ID Code:42
Deposited By:Robert Andrew Nyman
Deposited On:05 Dec 2003
Last Modified:06 Feb 2009 14:43

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