Research Highlights
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Quantum state manipulation detected by muon spin relaxation
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The muon spin relaxation technique utilises the muon spin to probe the local magnetism within a condensed matter system. Placing a coil of wire within the muon spin relaxation sample environment allows the application of magnetic excitation fields. By carefully controlling the frequency and amplitude of the excitation field, I showed how it is experimentally possible to manipulate quantum state populations allowing a spectroscopic probe of entangled quantum states.
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Physical Review Letters 129, 077201, (2022)
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Probing quantum states with thermodynamic measurements
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Alternating current magnetic susceptometry is usually thought of as a thermodynamic probe of magnetic susceptibility at finite frequencies. At very high probe frequencies, it is no longer possible for the magnetic spins to equilibrate though spin-spin or spin-lattice relaxation, and in this regime we measure a so-called isolated susceptibility which we have shown is a quantitative probe of state populations and concurrence.
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Physical Review B, 104, 014418 (2021)
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Electronic and magnetic structure of high-entropy alloys
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High-entropy alloys are metallic compounds that contain typically five or more chemical elements e.g. the so-called Cantor alloy NiFeCoCrMn. These crystals have long-range ordered lattices but possess complete site disorder. Using a combination of x-ray Compton scattering, x-ray magnetic circular dichroism spectroscopy and state-of-the-art electronic structure calculations, I probed the electronic and magnetic structure of these alloys.
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Physical Review B 102, 174405 (2020)
Physical Review Letters 124, 046402 (2020)
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Magnetic domain imaging and structural studies of Nd-Fe-B sintered magnets
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Nd-Fe-B permanent magnets with their high energy densities and large stray magnetic fields are one of the most technologically important materials of the modern age. While working at the SPring-8 synchrotron in Japan, I performed a number of experiments that used high-field x-ray magnetic microscopy to map how the magnetic domain structure changes throughout the demagnetisation process. I also performed temperature-dependent X-ray diffraction measurements to understand the changes in constituent phases throughout the sintering and annealing processes which vastly improve the performance of these magnets.
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Journal of Magnetism and Magnetic Materials 538, 168308 (2021)
Acta Materialia 205, 116517 (2021)
Acta Materialia 181, 530-536 (2019)
Acta Materialia 178, 90-98 (2019)
Acta Materialia 162, 1-9 (2019)
Physical Review Materials 2, 104413 (2018)
Journal of Synchrotron Radiation 25, 1444-1449 (2018)
Acta Materialia 154, 25-32 (2018)
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Electron-phonon superconductivity in intermetallic compounds
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Density functional perturbation theory is a powerful computational technique for studying the linear response of a material to some perturbation. For crystals, it allows us to calculate the frequencies of the lattice vibrations (phonons) and to determine the electron-phonon coupling which can be used to determine the superconducting critical temperature of conventional superconductors.
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Journal of Physics: Condensed Matter 28, 395702 (2016)
Philosophical Magazine 95, 1728-1737 (2015)
Journal of the Physical Society of Japan 83, 044710 (2014)
Superconductor Science and Technology 26, 085007 (2013)
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Keywords:
Electronic structure; Strongly correlated electron systems; Fermi surface; Magnetism; Magnetic frustration; Superconductivity; Low temperatures; X-ray Compton scattering; X-ray magnetic circular dichroism (XMCD); X-ray absorption spectroscopy (XAS); X-ray magnetic spectromicroscopy; Muon spin relaxation; Neutron diffraction; Positron annihilation; Magnetometry; Magnetic susceptometry; Density functional theory; Dynamical mean field theory; Electron-phonon coupling.