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Barton, Luke (2023) Sb Doped CuMnAs for Antiferromagnetic Spintronics. PhD thesis, University of Nottingham.

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Abstract

Enhancement of conventional electronic logic devices has been achieved with the consideration of electron spin, predominantly in ferromagnetic (FM) materials, for more than a decade. In computation and logic devices antiferromagnet (AF) materials have been a more recent hot topic after demonstrating the writing and reading of information with electrical current pulses on thin films of single crystal collinear AF CuMnAs. Desirable for their robust resistance to external fields, terahertz dynamics and lack of stray field, AFs have opened up new avenues for efficient spintronic devices.

In search of high quality, easily synthesised single crystal AF material and greater understanding of the spintronic variables accessible through manipulation of material properties thin film CuMnAs layers were grown via molecular beam epitaxy with an additional Sb doping flux. Producing CuMnAs(1-x)Sbx layers on GaAs at three levels of Sb flux the dopant was successfully incorporated into the tetragonal structure of CuMnAs with the preservation of crystal quality at lower fluxes. FM secondary phase growth was a ubiquitous issue amongst the layers and impacted the surface quality. Evidence of the magnetic phase transition from AF order to a paramagnetic material occurring at a lower temperature with Sb doping flux was found. Polarised X-ray microscopy revealed larger AF domains than observed in CuMnAs layers on the same substrate without Sb but was not yet able to match the highest quality CuMnAs. Recent trends in the electrical writing pulse replicated in the layers but significant improvement in the writing and reading of information was not achieved.

As magnetic materials have been investigated for their use in efficient next generation logical processing so they have also found potential use in improving efficiency through waste thermal energy recovery. Methods in characterising the efficiency of FM conductors for these applications have been applied to Fe79Ga21 thin films with a comparison to Fe, both capped with non-magnetic metals during sputter deposition. Fe79Ga21 holds promise for efficient thermal energy recovery by harnessing an established large anomalous Nernst effect and complimentary longitudinal spin Seebeck effect. While spin caloritronics measurements confirmed that Fe79Ga21 poses a significant improvement over Fe in waste thermal energy recovery the characterisation approach was found to be flawed. Anomalous peaks observed in the in-plane voltage of Fe samples during in-plane magnetic field sweeps are determined to be an artefact of magnetisation reversal within the thin film layer.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Rushforth, Andrew Campion, Richard
Keywords:	MBE growth, antiferromagnetic spintronics, Sb doping, thin film, spin caloritronics, galfenol, longitudinal spin Seebeck effect
Subjects:	Q Science > QC Physics > QC350 Optics. Light, including spectroscopy T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800 Electronics
Faculties/Schools:	UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID:	76653
Depositing User:	Barton, Luke
Date Deposited:	21 Mar 2024 13:29
Last Modified:	21 Mar 2024 13:29
URI:	https://eprints.nottingham.ac.uk/id/eprint/76653

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