Conor McKeever passed his viva!

We are delighted to announce that Conor McKeever successfully defended his thesis on high frequency dynamics of nano magnetic particles last Friday, with minor corrections. His external examiner was Richard Evans (University of York) and internal examiner was Dr Eros Mariani.

Conor is author/co-author on the following publications:

Excursion to California: Beam-time at the Advanced Light Source in Berkeley.

David Newman

XM² PGR David Newman (1st year, supervised by Prof Rob Hicken and Dr Mustafa Aziz ) recently went to the Advanced Light Source in Berkeley, California where he was using X-ray magnetic circular dichroism (XMCD), X-ray ferromagnetic resonance (XFMR) and other magnetic spectroscopic techniques to characterise spin currents in ferromagnetic/anti-ferromagnetic/ferromagnetic trilayer structures and probe the dynamics of exchange spring meta-materials. He kicked off his PhD project by learning more about the software used, developing his magnetic spectroscopy skills and generally gaining experience for future beam-times in Berkeley.

New Publication: A Broadband Stripline Technique for Characterizing Relative Permittivity and Permeability

Congratulations to the XM² PGRs Cameron Gallagher and Conor McKeever for their publication on “A Broadband Stripline Technique for Characterizing Relative Permittivity and Permeability” in IEEE Transactions on Microwave Theory and Techniques: 10.1109/TMTT.2018.2851563

Abstract:

We present a stripline design and calibration method allowing the extraction of relative permittivity of single dielectric samples in the 200-MHz-50-GHz range. The simultaneous extraction of relative permittivity and permeability is also illustrated by characterizing a set of samples comprising magnetic inclusions over the same frequency range. The calibration method involves the use of seven measurements of the stripline scattering parameters (S-parameters) with different length shorts inserted. From these measurements, it is possible to determine the reflections at the transition regions of the stripline to correct the measured S-parameters for characterization. By quantifying a range of samples with increasing percentage volume filling of barium titanate in polyurethane for the case of dielectric samples, and carbonyl iron powder for magnetic samples, this paper demonstrates a reliable method for the broadband characterization of composite materials.

New Publication: From colloidal CdSe quantum dots to microscale optically anisotropic supercrystals through bottom-up self-assembly

Congratulations to XM² PGR Ben Hogan (4th year) who is co-author on an article that outlines the analysis of quantum dot self-assembly into ordered superstructures, along with the evolution of their morphological and optical properties. The work has just been published as accepted manuscript in the Journal of Materials Chemistry C: https://pubs.rsc.org/en/content/articlepdf/2018/tc/c8tc04780d

Abstract

The development of fabrication techniques for novel nanostructured materials is one of the key tasks of modern materials science. One pathway to successfully complete this task is the bottom-up assembly of colloidal nanoparticles into ordered superstructures, possessing both the properties of individual nanoparticles and further novel properties resulting from their interactions. However, nanoparticle self-assembly depends on a variety of parameters, which makes the precise control of this process a complicated problem. Here, the time course of quantum dot (QD) self-assembly into ordered superstructures has been analyzed, along with the evolution of their morphological and optical properties. QD self-assembly occurs through two distinct stages (homo-and hetero-geneous), leading to the formation of supercrystals with a layered morphology. Analysis of the optical properties throughout the superstructures’ growth has shown that the absorption and photoluminescence (PL) bands are blue shifted, retaining almost the same PL lifetimes as in the initial QD solution. The supercrystals formed possess a further unique optical property caused by their layered morphology; namely, a four-fold symmetry characterized by strong birefringence. Such supercrystals may be used for the fabrication of microscale optical paths with high extinction coefficients and specific polarization properties for novel optoelectronic devices.

New Publication: Investigation of the coupling between tunable split-ring resonator

Congratulations to  XM² PGR Milo Baraclough (3rd year) who published his first paper ‘Investigation of the coupling between tunable split-ring resonators‘ in Physical Review B. This paper examines how the coupling between a passive and an active Split ring resonator changes as the active ring is tuned through the frequency of the passive ring: https://bit.ly/2JeXYbC.

Abstract

Passive resonant metamaterials are limited by the narrow-band nature of the resonances they support. Here we show that by incorporating an active component into the structure of the commonly used split-ring resonator it is possible to tune the resonance frequency of this type of metamaterial atom. We make use of this tunability to examine the interaction between two resonators, one passive and one active, as the resonance frequency of the active resonator is swept through that of the passive resonator. The resultant modes of this coupled system exhibit an anticrossing and, by changing the separation between, and relative orientation of, the split-ring resonators, we investigate how the magnetic and electric coupling terms change. We find that the relative orientation of the resonators significantly effects the strength of the coupling. Through both structural and active tuning we are able to alter the relative sizes and signs of the coupling terms. We hope that the nature of these changes will be of use to those designing large actively tunable metamaterial systems.

Figure 1: Schematic to illustrate the dipole moments associated with a split-ring resonator. The magnetic (blue) and electric (red) dipole moments of a split-ring resonator are shown, along with the direction of the instantaneous current around the ring (green). Note that the electric dipole moment is localized around the split region where there is maximal charge accumulation, while the magnetic dipole moment passes through the center of the ring due to the circulating currents.

“Seven brief lessons on Physics” – a translation into Urdu

XM2 PGR Zahid Hussain (3rd year) has committed a substantial amount of energy and time towards the translation of Carlo Rovelli’s book “Seven Brief Lessons on Physics” into Urdu, the national language of Pakistan. Three chapters have so far been published online:

http://www.laaltain.com/khob-sorat-tareen-nazria/

http://www.laaltain.com/roshani-k-zarat/

http://www.laaltain.com/kainat-ki-sakht/

“Seven Brief Lessons on Physics” was originally published in Italian in 2014 and has to date been translated into 41 languages.

Zahid aims to complete the other chapter translations over the next few months. Negotiations are ongoing with a renowned publisher who showed interest to publish the translations as a print in 2019.

New Publication: Probing Raman Scattering for Particle Tracking: a novel spectrocscopic analysis method

XM² PGR Ben Hogan (4th year) recently published his work onProbing Raman Scattering for Particle Tracking: a novel spectrocscopic analysis method‘ as the cover story in Micrcoscopy and Analysis (Sep/Oct 2018): https://lnkd.in/dmsEkyd

The article presents a summary of the current achievements of the team’s ongoing investigations using Raman spectroscopy to characterise and track particles of different materials. Microscopy and Analysis is the leading international journal for microscopists, with over 46,000 subscribers and 120,000 readers worldwide. The journal is distributed free of charge.

 

XM2 PGR social – food, fight and pub quiz winners!

Peter Inzani and Jess Brown are currently leading on the XM² PGR social events organisation.
They have recently coordinated a welcome celebration to the new cohort with all other CDT PGRs at Mill on the Exe.  Their summary of the evening:
“There was a delicious buffet and a pub quiz. After 6 rounds of trivia, physics knowledge, music lyrics, flags and a very close fight, one team came out on top – congratulations to the winners, Frank, Lizzie, Shane, Ros and Milo, and enjoy your well-deserved chocolate! Our next big social will be our Christmas meal in December.”
Thanks to Jess and Peter for organising the event, and congratulations to the pub quiz winners – I am reassured that the “very close fight” bit is not to be taken too literally and all PGRs returned to their studies safe and sound.
Lizzie, Shane, Ros, Milo, and Frank (not on the ground for any other reasons than an entertaining picture!) – the pub quiz winners of 2018 🙂

Sam Shelley & Tim Spicer passed their vivas! Congratulations!

 

Tim Spicer at the ICMM conference http://blogs.exeter.ac.uk/xm2news/icmmbeyondaphd/
Sam Shelley submitting his PhD thesis.

Very many contragulations to both Sam Shelley and Tim Spicer who have recently passed their respective viva with minor corrections. Well done both!

Sam will continue to contribute his expertise at the University of Exeter as a postdoc. His work on “The Control of Fluid Flow Using Metamaterials Concepts”  (supervised by Roy Sambles (FRS), Alastair Hibbins and Simon Horsley) was assessed by Stephen Turnock (Southampton) and Sean Matt (Exeter).

Timothy Spicer’s work on “Excitation of picosecond magnetization dynamics by spin transfer torque” (supervised by Rob Hicken and Volodymyr Kruglyak)  was assessed by Thomas Moore (Leeds) and Euan Hendry (Exeter). We have recently encouraged him to consider a role at Flann Microwave and are awaiting the outcome of this.

We’d like to thank the assessors for their time committment and congratulate the PGRs once again to their great achievement.