I06-Nanoscience
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O. J.
Amin
,
S. F.
Poole
,
S.
Reimers
,
L. X.
Barton
,
A.
Dal Din
,
F.
Maccherozzi
,
S. S.
Dhesi
,
V.
Novák
,
F.
Krizek
,
J. S.
Chauhan
,
R. P.
Campion
,
A. W.
Rushforth
,
T.
Jungwirth
,
O. A.
Tretiakov
,
K. W.
Edmonds
,
P.
Wadley
Diamond Proposal Number(s):
[26255, 27845]
Open Access
Abstract: Topologically protected magnetic textures are promising candidates for information carriers in future memory devices, as they can be efficiently propelled at very high velocities using current-induced spin torques. These textures—nanoscale whirls in the magnetic order—include skyrmions, half-skyrmions (merons) and their antiparticles. Antiferromagnets have been shown to host versions of these textures that have high potential for terahertz dynamics, deflection-free motion and improved size scaling due to the absence of stray field. Here we show that topological spin textures, merons and antimerons, can be generated at room temperature and reversibly moved using electrical pulses in thin-film CuMnAs, a semimetallic antiferromagnet that is a testbed system for spintronic applications. The merons and antimerons are localized on 180° domain walls, and move in the direction of the current pulses. The electrical generation and manipulation of antiferromagnetic merons is a crucial step towards realizing the full potential of antiferromagnetic thin films as active components in high-density, high-speed magnetic memory devices.
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May 2023
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I10-Beamline for Advanced Dichroism
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Diamond Proposal Number(s):
[21872, 27487]
Open Access
Abstract: The topological surface states (TSSs) in topological insulators (TIs) offer exciting prospects for dissipationless spin transport. Common spin-based devices, such as spin valves, rely on trilayer structures in which a non-magnetic (NM) layer is sandwiched between two ferromagnetic (FM) layers. The major disadvantage of using high-quality single-crystalline TI films in this context is that a single pair of spin-momentum locked channels spans across the entire film, meaning that only a very small spin current can be pumped from one FM to the other, along the side walls of the film. On the other hand, using nanocrystalline TI films, in which the grains are large enough to avoid hybridization of the TSSs, will effectively increase the number of spin channels available for spin pumping. Here, we used an element-selective, x-ray based ferromagnetic resonance technique to demonstrate spin pumping from a FM layer at resonance through the TI layer and into the FM spin sink.
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Mar 2023
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I19-Small Molecule Single Crystal Diffraction
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Haofan
Yang
,
Chao
Li
,
Tao
Liu
,
Thomas
Fellowes
,
Samantha Y.
Chong
,
Luca
Catalano
,
Mounib
Bahri
,
Weiwei
Zhang
,
Yongjie
Xu
,
Lunjie
Liu
,
Wei
Zhao
,
Adrian M.
Gardner
,
Rob
Clowes
,
Nigel D.
Browning
,
Xiaobo
Li
,
Alexander J.
Cowan
,
Andrew I.
Cooper
Abstract: Molecular packing controls optoelectronic properties in organic molecular nanomaterials. Here we report a donor–acceptor organic molecule (2,6-bis(4-cyanophenyl)-4-(9-phenyl-9H-carbazol-3-yl)pyridine-3,5-dicarbonitrile) that exhibits two aggregate states in aqueous dispersions: amorphous nanospheres and ordered nanofibres with π–π molecular stacking. The nanofibres promote sacrificial photocatalytic H2 production (31.85 mmol g−1 h−1) while the nanospheres produce hydrogen peroxide (H2O2) (3.20 mmol g−1 h−1 in the presence of O2). This is the first example of an organic photocatalyst that can be directed to produce these two different solar fuels simply by changing the molecular packing. These different packings affect energy band levels, the extent of excited state delocalization, the excited state dynamics, charge transfer to O2 and the light absorption profile. We use a combination of structural and photophysical measurements to understand how this influences photocatalytic selectivity. This illustrates the potential to achieve multiple photocatalytic functionalities with a single organic molecule by engineering nanomorphology and solid-state packing.
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Jan 2023
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Ian
Vidamour
,
Matthew O. A.
Ellis
,
David
Griffin
,
Guru
Venkat
,
Charles
Swindells
,
Richard W. S.
Dawidek
,
Thomas J
Broomhall
,
Nina-Juliane
Steinke
,
Joshaniel
Cooper
,
Francesco
Maccherozzi
,
Sarnjeet
Dhesi
,
Susan
Stepney
,
Eleni
Vasilaki
,
Dan A.
Allwood
,
Tom James
Hayward
Open Access
Abstract: Devices based on arrays of interconnected magnetic nano-rings with emergent magnetization dynamics have recently been proposed for use in reservoir computing applications, but for them to be computationally useful it must be possible to optimise their dynamical responses. Here, we use a phenomenological model to demonstrate that such reservoirs can be optimised for classification tasks by tuning hyperparameters that control the scaling and input-rate of data into the system using rotating magnetic fields. We use task-independent metrics to assess the rings' computational capabilities at each set of these hyperparameters and show how these metrics correlate directly to performance in spoken and written digit recognition tasks. We then show that these metrics, and performance in tasks, can be further improved by expanding the reservoir's output to include multiple, concurrent measures of the ring arrays' magnetic states.
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Aug 2022
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I14-Hard X-ray Nanoprobe
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Kyle
Frohna
,
Miguel
Anaya
,
Stuart
Macpherson
,
Jooyoung
Sung
,
Tiarnan A. S.
Doherty
,
Yu-Hsien
Chiang
,
Andrew J.
Winchester
,
Kieran W. P.
Orr
,
Julia E.
Parker
,
Paul D.
Quinn
,
Keshav M.
Dani
,
Akshay
Rao
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[19023, 20420]
Abstract: Halide perovskites perform remarkably in optoelectronic devices. However, this exceptional performance is striking given that perovskites exhibit deep charge-carrier traps and spatial compositional and structural heterogeneity, all of which should be detrimental to performance. Here, we resolve this long-standing paradox by providing a global visualization of the nanoscale chemical, structural and optoelectronic landscape in halide perovskite devices, made possible through the development of a new suite of correlative, multimodal microscopy measurements combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements. We show that compositional disorder dominates the optoelectronic response over a weaker influence of nanoscale strain variations even of large magnitude. Nanoscale compositional gradients drive carrier funnelling onto local regions associated with low electronic disorder, drawing carrier recombination away from trap clusters associated with electronic disorder and leading to high local photoluminescence quantum efficiency. These measurements reveal a global picture of the competitive nanoscale landscape, which endows enhanced defect tolerance in devices through spatial chemical disorder that outcompetes both electronic and structural disorder.
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Nov 2021
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William
Liu
,
Salida
Mirzoeva
,
Ye
Yuan
,
Junjing
Deng
,
Si
Chen
,
Barry
Lai
,
Stefan
Vogt
,
Karna
Shah
,
Rahul
Shroff
,
Reiner
Bleher
,
Qiaoling
Jin
,
Nghia
Vo
,
Remon
Bazak
,
Carissa
Ritner
,
Stanley
Gutionov
,
Sumita
Raha
,
Julia
Sedlmair
,
Carol
Hirschmugl
,
Chris
Jacobsen
,
Tatjana
Paunesku
,
John
Kalapurkal
,
Gayle E.
Woloschak
Open Access
Abstract: Background: Neuroblastoma is the most common extracranial solid malignancy in childhood which, despite the current progress in radiotherapy and chemotherapy protocols, still has a high mortality rate in high risk tumors. Nanomedicine offers excit- ing and unexploited opportunities to overcome the shortcomings of conventional medicine. The photocatalytic properties of Fe O core-TiO shell nanocomposites and
3 4 2
their potential for cell specific targeting suggest that nanoconstructs produced using
Fe3O4 core-TiO2 shell nanocomposites could be used to enhance radiation effects in neuroblastoma. In this study, we evaluated bare, metaiodobenzylguanidine (MIBG) and 3,4-Dihydroxyphenylacetic acid (DOPAC) coated Fe3O4@TiO2 as potential radiosensitiz- ers for neuroblastoma in vitro.
Results: The uptake of bare and MIBG coated nanocomposites modestly sensitized neuroblastoma cells to ionizing radiation. Conversely, cells exposed to DOPAC coated nanocomposites exhibited a five-fold enhanced sensitivity to radiation, increased numbers of radiation induced DNA double-strand breaks, and apoptotic cell death. The addition of a peptide mimic of the epidermal growth factor (EGF) to nanoconju- gates coated with MIBG altered their intracellular distribution. Cryo X-ray fluorescence microscopy tomography of frozen hydrated cells treated with these nanoconjugates revealed cytoplasmic as well as nuclear distribution of the nanoconstructs.
Conclusions: The intracellular distribution pattern of different nanoconjugates used in this study was different for different nanoconjugate surface molecules. Cells exposed to DOPAC covered nanoconjugates showed the smallest nanoconjugate uptake,
with the most prominent pattern of large intracellular aggregates. Interestingly, cells treated with this nanoconjugate also showed the most pronounced radiosensitiza- tion effect in combination with the external beam x-ray irradiation. Further studies
are necessary to evaluate mechanistic basis for this increased radiosensitization effect. Preliminary studies with the nanoparticles carrying an EGF mimicking peptide showed.
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May 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[14099]
Open Access
Abstract: Two-dimensional (2D) hexagonal boron nitride (h-BN) is becoming increasingly interesting for wider engineering applications. Thermal exfoliation is being suggested as a facile technology to produce large quantities of 2D h-BN. Further optimization of the process requires fundamental understanding of the exfoliation mechanism, which is hardly realized by ex-situ techniques. In this study, time resolved in-situ synchrotron X-ray powder diffraction experiments are conducted while heat treating bulk h-BN up to 1273 K. During the heating process, linear expansion of c-axis is observed and the contraction of a-axis up to around 750 K is consistent with previous research. However, a changing behavior from contraction to expansion in a- axis direction is newly observed when heating over 750 K. With the consideration of previous thermally oxidation studies, a hypothesis of thermal assisted exfoliation with oxygen interstitial and substitution of nitrogen at high temperature is proposed.
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Nov 2020
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Michaela
Sulikova
,
Zuzana
Molčanová
,
Beata
Ballóková
,
Juraj
Durisin
,
Slávka
Martinková
,
Dagmara
Varcholová
,
Stefan
Michalik
,
Robert Tang
Kong
,
Logan
Ward
,
Apurva
Mehta
,
Katarína
Sulova
,
Miloš
Fejercak
,
Andrea
Lachova
,
Róbert
Džunda
,
Karel
Saksl
Abstract: In surgery, in addition to joint replacement, which requires permanent implantation of the prosthesis into the human body, there are many other clinical cases where fixation or mechanical support are only temporarily needed during the healing process of the injured or pathological tissue. In this case, biodegradable materials are the optimal choice as these materials do their job and degrade in the human body thereafter. Amorphous magnesium-zinc based alloys are nowadays a very promising group of metallic glasses (MGs). Unfortunately, the brittleness of Mg-Zn MGs and poor glass forming ability (GFA) have hindered their further application. We have developed a composition series of completely new (not published) ternary Mg-Zn-Sr alloys with attractive properties in terms of possible future applications (density comparable to human bones, wide supercooled liquid region, low rate of degradability, etc.). These ternary alloys will serve as precursors for design of future highly alloyed systems with tuned mechanical properties and dissociation rate in human body.
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Nov 2020
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[13740]
Open Access
Abstract: We studied the structural and electronic properties of 2,3,9,10-tetrafluoropentacene (F4PEN) on Ag(111) via X-ray standing waves (XSW), low-energy electron diffraction (LEED) as well as ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS). XSW revealed that the adsorption distances of F4PEN in (sub)monolayers on Ag(111) were 3.00 Å for carbon atoms and 3.05 Å for fluorine atoms. The F4PEN monolayer was essentially lying on Ag(111), and multilayers adopted π-stacking. Our study shed light not only on the F4PEN–Ag(111) interface but also on the fundamental adsorption behavior of fluorinated pentacene derivatives on metals in the context of interface energetics and growth mode.
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Sep 2020
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E02-JEM ARM 300CF
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Astrid
Weston
,
Yichao
Zou
,
Vladimir
Enaldiev
,
Alex
Summerfield
,
Nicholas
Clark
,
Viktor
Zólyomi
,
Abigail
Graham
,
Celal
Yelgel
,
Samuel
Magorrian
,
Mingwei
Zhou
,
Johanna
Zultak
,
David
Hopkinson
,
Alexei
Barinov
,
Thomas H.
Bointon
,
Andrey
Kretinin
,
Neil R.
Wilson
,
Peter H.
Beton
,
Vladimir I.
Fal’ko
,
Sarah J.
Haigh
,
Roman
Gorbachev
Diamond Proposal Number(s):
[19315, 21597]
Abstract: Van der Waals heterostructures form a unique class of layered artificial solids in which physical properties can be manipulated through controlled composition, order and relative rotation of adjacent atomic planes. Here we use atomic-resolution transmission electron microscopy to reveal the lattice reconstruction in twisted bilayers of the transition metal dichalcogenides, MoS2 and WS2. For twisted 3R bilayers, a tessellated pattern of mirror-reflected triangular 3R domains emerges, separated by a network of partial dislocations for twist angles θ < 2°. The electronic properties of these 3R domains, featuring layer-polarized conduction-band states caused by lack of both inversion and mirror symmetry, appear to be qualitatively different from those of 2H transition metal dichalcogenides. For twisted 2H bilayers, stable 2H domains dominate, with nuclei of a second metastable phase. This appears as a kagome-like pattern at θ ≈ 2°, transitioning at θ → 0 to a hexagonal array of screw dislocations separating large-area 2H domains. Tunnelling measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties.
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May 2020
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