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James Wilman


I graduated from The University of Sheffield in 2012 with an MPhys degree and I am currently studying for a PhD at The University of Nottingham under the supervision of Dr Walter Kockenberger, Dr. Lyudmila Turyanska and Dr Josef Granwehr.



Developing magnetic resonance instrumentation and multidimensional methods to study samples with mixed magnetic phases

Paramagnetically doped diamagnetic materials have a wide range of applications, such as for heterogeneous catalysis or as functional materials. Identifying the structural and mechanistic features that are responsible for their properties remains a challenging task, yet is indispensable for a systematic improvement of existing materials or for their adaptation towards novel applications. Temperature dependent magnetic susceptibility measurements, where an external magnetic field is modulated and the response from a magnetic material is measured with a coil parallel to the external field, are commonly used for studying the magnetism and indirectly also the structure of such materials, especially for high dopant concentrations and for dopants that tend to form clusters. However, for complex heterogeneous materials, conventional magnetic susceptibility experiments merely provide a statistical indication of the dominant phases with different degree of ordering, e.g. Paramagnetic and superparamagnetic phases, coexist and, potentially, interact with each other.

The same coil oriented parallel to the external magnetic field that is used to detect magnetic ordering in a susceptibility experiment can also be used for detecting magnetic resonance. In my project, methods and instrumentation will be developed to identify and quantify interactions between paramagnetic and ordered magnetic phases. A modular multi-purpose probe will be designed and built that can be set up for a very fast response time or, alternatively, to facilitate fast field jump experiments. In addition, generating field jumps requires setting up the electronics for fast switching of large current pulses. This setup will then be used to identify interactions between different magnetic phases by correlating the response of a sample to mw irradiation with its response to a field jump.  

Electron Spin Resonance of Tuneable Magnetically Doped Colloidal Quantum Dots

Controlling the size, shape or chemical composition of quantum dots allows for the manipulation of electronic, optical and magnetic properties leading to the possibility for novel applications. However, the exact effect of changing the quantum dot structure and composition, and of incorporating different magnetic impurities, is as yet unknown and requires further study.

Colloidal quantum dots (QDs) allow for the tuning of dopant concentration as well as flexibility in the engineering of the surrounding medium. This work focuses on the potential of a new type of magnetically doped colloidal QD, PbS:Mn, for use in quantum information processing (QIP). The Mn2+ concentration and QD morphology are used as a tool to investigate the limiting factors and mechanisms affecting the duration of the phase memory time (TM). Electron spin resonance techniques will be used in order to determine the phase memory time and to establish a means of initializing, manipulating and reading-out qubits.


Publications

Fabrizio Moro, Lyudmila Turyanska, James Wilman, Alistair J. Fielding, Michael W. Fay, Josef Granwehr, Amalia Patanè; Electron spin coherence near room temperature in magnetic quantum dots. Sci. Rep. 5, 10855; doi: 10.1038/srep10855 (2015).

Fabrizio Moro, Lyudmila Turyanska, James Wilman, Huw E. L. Williams, Alistair J. Fielding, Amalia Patanè; Surface Sensing of Quantum Dots by Electron Spins. Nano Lett., 2016, 16 (10), pp 6343–6348; DOI: 10.1021/acs.nanolett.6b02727


Contact:
ppxjw2 at nottingham dot uk dot ac