|
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Xiyang
Li
,
Shilei
Zhang
,
Hang
Li
,
Diego
Alba Venero
,
Jonathan S
White
,
Robert
Cubitt
,
Qingzhen
Huang
,
Jie
Chen
,
Lunhua
He
,
Gerrit
Van Der Laan
,
Wenhong
Wang
,
Thorsten
Hesjedal
,
Fangwei
Wang
Open Access
Abstract: A biskyrmion consists of two bound, topologically stable, skyrmion spin textures. These coffee‐bean‐shaped objects are observed in real space in thin plates using Lorentz transmission electron microscopy (LTEM). From LTEM imaging alone, it is not clear whether biskyrmions are surface‐confined objects, or, analogous to skyrmions in non-centrosymmetric helimagnets, 3D tube‐like structures in a bulk sample. Here, the biskyrmion form factor is investigated in single‐ and polycrystalline‐MnNiGa samples using small‐angle neutron scattering. It is found that biskyrmions are not long‐range ordered, not even in single crystals. Surprisingly all of the disordered biskyrmions have their in‐plane symmetry axis aligned along certain directions, governed by the magneto-crystalline anisotropy. This anisotropic nature of biskyrmions may be further exploited to encode information.
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Mar 2019
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I10-Beamline for Advanced Dichroism
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Wenjing
Li
,
Iuliia
Bykova
,
Shilei
Zhang
,
Guoqiang
Yu
,
Riccardo
Tomasello
,
Mario
Carpentieri
,
Yizhou
Liu
,
Yao
Guang
,
Joachim
Gräfe
,
Markus
Weigand
,
David M.
Burn
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Zhengren
Yan
,
Jiafeng
Feng
,
Caihua
Wan
,
Jinwu
Wei
,
Xiao
Wang
,
Xiaomin
Zhang
,
Hongjun
Xu
,
Chenyang
Guo
,
Hongxiang
Wei
,
Giovanni
Finocchio
,
Xiufeng
Han
,
Gisela
Schütz
Diamond Proposal Number(s):
[18898]
Abstract: Room temperature magnetic skyrmions in magnetic multilayers are considered as information carriers for future spintronic applications. Currently, a detailed understanding of the skyrmion stabilization mechanisms is still lacking in these systems. To gain more insight, it is first and foremost essential to determine the full real-space spin configuration. Here, two advanced X-ray techniques are applied, based on magnetic circular dichroism, to investigate the spin textures of skyrmions in [Ta/CoFeB/MgO]n multilayers. First, by using ptychography, a high-resolution diffraction imaging technique, the 2D out-of-plane spin profile of skyrmions with a spatial resolution of 10 nm is determined. Second, by performing circular dichroism in resonant elastic X-ray scattering, it is demonstrated that the chirality of the magnetic structure undergoes a depthdependent evolution. This suggests that the skyrmion structure is a complex 3D structure rather than an identical planar texture throughout the layer stack. The analyses of the spin textures confirm the theoretical predictions that the dipole–dipole interactions together with the external magnetic field play an important role in stabilizing sub-100 nm diameter skyrmions and the hybrid structure of the skyrmion domain wall. Our combined X-ray-based approach opens the door for in-depth studies of magnetic skyrmion systems, which allows for precise engineering of optimized skyrmion heterostructures.
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Feb 2019
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[7223]
Abstract: Efficient vacuum‐processed organic light‐emitting diodes are fabricated using a carbene–metal–amide material, CMA1. An electroluminescence (EL) external quantum efficiency of 23% is achieved in a host‐free emissive layer comprising pure CMA1. Furthermore external quantum efficiencies of up to 26.9% are achieved in host–guest emissive layers. EL spectra are found to depend on both the emissive‐layer doping concentration and the choice of host material, enabling tuning of emission color from mid‐green (Commission Internationale de l'Éclairage co‐ordinates [0.24, 0.46]) to sky blue ([0.22 0.35]) without changing dopant. This tuning is achieved without compromising luminescence efficiency (>80%) while maintaining a short radiative lifetime of triplets (<1 μs).
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Jul 2018
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I09-Surface and Interface Structural Analysis
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Philipp
Scheiderer
,
Matthias
Schmitt
,
Judith
Gabel
,
Michael
Zapf
,
Martin
Stuebinger
,
Philipp
Schütz
,
Lenart
Dudy
,
Christoph
Schlueter
,
Tien-lin
Lee
,
Michael
Sing
,
Ralph
Claessen
Diamond Proposal Number(s):
[14106, 15200, 15856, 18372]
Abstract: The Mott transistor is a paradigm for a new class of electronic devices—often referred to by the term Mottronics—which are based on charge correlations between the electrons. Since correlation‐induced insulating phases of most oxide compounds are usually very robust, new methods have to be developed to push such materials right to the boundary to the metallic phase in order to enable the metal–insulator transition to be switched by electric gating. Here, it is demonstrated that thin films of the prototypical Mott insulator LaTiO3 grown by pulsed laser deposition under oxygen atmosphere are readily tuned by excess oxygen doping across the line of the band‐filling controlled Mott transition in the electronic phase diagram. The detected insulator to metal transition is characterized by a strong change in resistivity of several orders of magnitude. The use of suitable substrates and capping layers to inhibit oxygen diffusion facilitates full control of the oxygen content and renders the films stable against exposure to ambient conditions. These achievements represent a significant advancement in control and tuning of the electronic properties of LaTiO3+x thin films making it a promising channel material in future Mottronic devices.
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May 2018
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I07-Surface & interface diffraction
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Víctor
Rubio-giménez
,
Marta
Galbiati
,
Javier
Castells-gil
,
Neyvis
Almora-barrios
,
José
Navarro-sánchez
,
Garin
Escorcia-ariza
,
Michele
Mattera
,
Thomas
Arnold
,
Jonathan
Rawle
,
Sergio
Tatay
,
Eugenio
Coronado
,
Carlos
Marti-gastaldo
Diamond Proposal Number(s):
[14495]
Abstract: Though generally considered insulating, recent progress on the discovery of conductive porous metal–organic frameworks (MOFs) offers new opportunities for their integration as electroactive components in electronic devices. Compared to classical semiconductors, these metal–organic hybrids combine the crystallinity of inorganic materials with easier chemical functionalization and processability. Still, future development depends on the ability to produce high-quality films with fine control over their orientation, crystallinity, homogeneity, and thickness. Here self-assembled monolayer substrate modification and bottom-up techniques are used to produce preferentially oriented, ultrathin, conductive films of Cu-CAT-1. The approach permits to fabricate and study the electrical response of MOF-based devices incorporating the thinnest MOF film reported thus far (10 nm thick).
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Jan 2018
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I07-Surface & interface diffraction
|
Baodan
Zhao
,
Mojtaba
Abdi-jalebi
,
Maxim
Tabachnyk
,
Hugh
Glass
,
Varun S.
Kamboj
,
Wanyi Andrew
Nie
,
J.
Pearson
,
Yuttapoom
Puttisong
,
Karl C.
Gödel
,
Harvey E.
Beere
,
David A.
Ritchie
,
Aditya D.
Mohite
,
Sian E.
Dutton
,
Richard H.
Friend
,
Aditya
Sadhanala
Diamond Proposal Number(s):
[12436]
Open Access
Abstract: Low-bandgap CH3NH3(Pb x Sn1– x )I3 (0 ≤ x ≤ 1) hybrid perovskites (e.g., ≈1.5–1.1 eV) demonstrating high surface coverage and superior optoelectronic properties have been fabricated. State-of-the-art photovoltaic (PV) performance is reported with power conversion efficiencies approaching 10% in planar heterojunction architecture with small (<450 meV) energy loss compared to the bandgap and high (>100 cm2 V−1 s−1) intrinsic carrier mobilities.
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Nov 2016
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I07-Surface & interface diffraction
|
Diamond Proposal Number(s):
[12895]
Abstract: A novel strategy for direct photoalignment of molecular materials using optothermal re-orientation is introduced. Photoalignment for molecular materials such as the organic semiconductor tetracene is shown, without relying on additional photoreactive dopants or alignment layers. Patterning and polarized light emission, e.g., for polarized organic light emitting diodes is demonstrated.
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Nov 2016
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I06-Nanoscience
|
Heng-jui
Liu
,
Jheng-cyuan
Lin
,
Yue-wen
Fang
,
Jing-ching
Wang
,
Bo-chao
Huang
,
Xiang
Gao
,
Rong
Huang
,
Philip R.
Dean
,
Peter
Hatton
,
Yi-ying
Chin
,
Hong-ji
Lin
,
Chien-te
Chen
,
Yuichi
Ikuhara
,
Ya-ping
Chiu
,
Chia-seng
Chang
,
Chun-gang
Duan
,
Qing
He
,
Ying-hao
Chu
Abstract: A novel artificially created MnO2 monolayer system is demonstrated in atomically controlled epitaxial perovskite heterostructures. With careful design of different electrostatic boundary conditions, a magnetic transition as well as a metal–insulator transition of the MnO2 monolayer is unveiled, providing a fundamental understanding of dimensionality-confined strongly correlated electron systems and a direction to design new electronic devices.
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Nov 2016
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I06-Nanoscience
|
Shengfu
Yang
,
Cheng
Feng
,
Daniel
Spence
,
Aula M. A. A.
Al Hindawi
,
Elspeth
Latimer
,
Andrew M.
Ellis
,
Chris
Binns
,
Davide
Peddis
,
Sarnjeet S.
Dhesi
,
Liying
Zhang
,
Yafei
Zhang
,
Kalliopi N.
Trohidou
,
Marianna
Vasilakaki
,
Nikolaos
Ntallis
,
Ian
Maclaren
,
Frank M. F.
De Groot
Diamond Proposal Number(s):
[11485]
Open Access
Abstract: Chromium nanoparticles are formed using superfluid helium droplets as the nanoreactors, which are strongly ferromagnetic. The transition from antiferromagentism to ferromagnetism is attributed to atomic scale disorder in chromium nanoparticles, leading to abundant unbalanced surface spins. Theoretical modeling confirms a frustrated aggregation process in superfluid helium due to the antiferromagnetic nature of chromium.
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Oct 2016
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Abstract: Insulating SrTiO3 (STO) can host 2D electron systems (2DESs) on its surfaces, caused by oxygen defects. This study shows that the STO surface exhibits phase separation once the 2DES is formed and relates this inhomogeneity to recently reported magnetic order at STO surfaces and interfaces. The results open pathways to exploit oxygen defects for engineering the electronic and magnetic properties of oxides.
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Sep 2016
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