posted on 2021-12-02, 11:50authored byChristopher D.W. Cox
The growth and optimisation of Co2MnSi thin films fabricated by PLD have been
investigated of application in spin Seebeck Effect (SSE) devices. The results of
structural, magnetic and thermal transport measurement of the optimisation of
deposition and post-deposition annealing treatments have been presented. In addition, the Co2MnSi films were fabricated as part of SSE devices, [Co2MnSi:Pt]n
multilayers, which were fabricated and analysed to investigate the possibility of an
enhancement in the thermoelectric signal. The films have been analysed using x-ray
diffraction (XRD), x-ray reflectivity (XRR), polarised neutron reflectometry (PNR),
magnetometry (SQuID, VSM-SQuID and MOKE) and the contributions from the
anomalous Nernst and spin Seebeck effects were analysed on in-house thermal transport equipment.
The Co2MnSi films deposited on glass were found to exhibit a development of
the atomic site ordering with both deposition and annealing temperature. At an
annealing temperature of 300◦C the films grew with a (220) texture and in the B2
phase. At an annealing temperature of 450◦C the films grew with a (220) texture
and in the L21 phase. The SSE measurements suggested that bilayers annealed at
300◦C exhibited a larger response than those annealed at 450◦C because the interface
quality and width was a more determinant factor in the SSE than the bulk atomic
ordering of the film.
The multilayers annealed at 450◦C showed absolutely no enhancement from the
single bilayer, echoing the need for interface engineering rather than spin generation
optimisation. However, the multilayers annealed at 300◦C (with cleaner interfaces)
exhibited a thermoelectric enhancement, twice that of the single bilayers.
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Publication date
2018
Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.