Research Highlights
Quantum state manipulation detected by muon spin relaxation
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.
Physical Review Letters 129, 077201, (2022)
Probing quantum states with thermodynamic measurements
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.
Physical Review B, 104, 014418 (2021)
Electronic and magnetic structure of high-entropy alloys
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.
Physical Review B 102, 174405 (2020)
Physical Review Letters 124, 046402 (2020)
Magnetic domain imaging and structural studies of Nd-Fe-B sintered magnets
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.
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)
Electron-phonon superconductivity in intermetallic compounds
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.
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)
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.