I10-Beamline for Advanced Dichroism
|
Sheng-qun
Su
,
Shu-qi
Wu
,
Michael L.
Baker
,
Peter
Bencok
,
Nobuaki
Azuma
,
Yuji
Miyazaki
,
Motohiro
Nakano
,
Soonchul
Kang
,
Yoshihito
Shiota
,
Kazunari
Yoshizawa
,
Shinji
Kanegawa
,
Osamu
Sato
Diamond Proposal Number(s):
[17723]
Abstract: Orbital angular momentum plays a vital role in various applications, especially magnetic and spintronic properties. There-fore, controlling orbital angular momentum is of paramount importance to both fundamental science and new technologi-cal applications. Many attempts have been made to modulate the ligand-field induced quenching effects of orbital angular momentum to manipulate magnetic properties. However, to date, reported changes in the magnitude of orbital angular momentum are small in both molecular and solid-state magnetic materials. Moreover, no effective methods currently exist to modulate orbital angular momentum. Here, we report a dynamic bond approach to realize a large change in orbital angu-lar momentum. We have developed a Co(II) complex that exhibits coordination number switching between six and seven. This cooperative dynamic bond switching induces considerable modulation of the ligand field, thereby leading to substantial quenching and restoration of the orbital angular momentum. This switching mechanism is entirely different from those of spin-crossover and valence tautomeric compounds, which exhibit switching in spin multiplicity.
|
Jun 2020
|
|
I08-Scanning X-ray Microscopy beamline (SXM)
I10-Beamline for Advanced Dichroism
|
Open Access
Abstract: Atypical low-oxidation-state iron phases in Alzheimer’s disease (AD) pathology are implicated in disease pathogenesis, as they may promote elevated redox activity and convey toxicity. However, the origin of low-oxidation-state iron and the pathways responsible for its formation and evolution remain unresolved. Here we investigate the interaction of the AD peptide β-amyloid (Aβ) with the iron storage protein ferritin, to establish whether interactions between these two species are a potential source of low-oxidation-state iron in AD. Using X-ray spectromicroscopy and electron microscopy we found that the co-aggregation of Aβ and ferritin resulted in the conversion of ferritin’s inert ferric core into more reactive low-oxidation-states. Such findings strongly implicate Aβ in the altered iron handling and increased oxidative stress observed in AD pathogenesis. These amyloid-associated iron phases have biomarker potential to assist with disease diagnosis and staging, and may act as targets for therapies designed to lower oxidative stress in AD tissue.
|
Jun 2020
|
|
I05-ARPES
I10-Beamline for Advanced Dichroism
|
Matthew D.
Watson
,
Igor
Markovic
,
Federico
Mazzola
,
Akhil
Rajan
,
Edgar A.
Morales
,
David
Burn
,
Thorsten
Hesjedal
,
Gerrit
Van Der Laan
,
Saumya
Mukherjee
,
Timur K.
Kim
,
Chiara
Bigi
,
Ivana
Vobornik
,
Monica
Ciomaga Hatnean
,
Geetha
Balakrishnan
,
Philip D. C.
King
Diamond Proposal Number(s):
[21986, 22794, 23785]
Abstract: We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, CrGeTe3. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through TC. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te 5p and the Cr eg orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr t2g states that carry the majority of the spin moment. The t2g states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.
|
May 2020
|
|
I10-Beamline for Advanced Dichroism
|
Maciej
Dabrowski
,
Takafumi
Nakano
,
David
Burn
,
Andreas
Frisk
,
David G.
Newman
,
Christoph
Klewe
,
Qian
Li
,
Mengmeng
Yang
,
Padraic
Shafer
,
Elke
Arenholz
,
Thorsten
Hesjedal
,
Gerrit
Van Der Laan
,
Zi Q.
Qiu
,
Robert J.
Hicken
Diamond Proposal Number(s):
[17745, 19116, 20760]
Abstract: Insulating antiferromagnets have recently emerged as efficient and robust conductors of spin current. Element-specific and phase-resolved x-ray ferromagnetic resonance has been used to probe the injection and transmission of ac spin current through thin epitaxial NiO(001) layers. The spin current is found to be mediated by coherent evanescent spin waves of GHz frequency, rather than propagating magnons of THz frequency, paving the way towards coherent control of the phase and amplitude of spin currents within an antiferromagnetic insulator at room temperature.
|
May 2020
|
|
I10-Beamline for Advanced Dichroism
|
Shu-qi
Wu
,
Meijiao
Liu
,
Kaige
Gao
,
Shinji
Kanegawa
,
Yusuke
Horie
,
Genki
Aoyama
,
Hajime
Okajima
,
Akira
Sakamoto
,
Michael L.
Baker
,
Myron S.
Huzan
,
Peter
Bencok
,
Tsukasa
Abe
,
Yoshihito
Shiota
,
Kazunari
Yoshizawa
,
Wenhuang
Xu
,
Hui-zhong
Kou
,
Osamu
Sato
Diamond Proposal Number(s):
[21117]
Open Access
Abstract: Polarization change induced by directional electron transfer attracts considerable attention owing to its fast switching rate and potential light control. Here, we investigate electronic pyroelectricity in the crystal of a mononuclear complex, [Co(phendiox)(rac-cth)](ClO4)·0.5EtOH (1·0.5EtOH, H2phendiox = 9, 10-dihydroxyphenanthrene, rac-cth = racemic 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane), which undergoes a two-step valence tautomerism (VT). Correspondingly, pyroelectric current exhibits double peaks in the same temperature domain with the polarization change consistent with the change in dipole moments during the VT process. Time-resolved Infrared (IR) spectroscopy shows that the photo-induced metastable state can be generated within 150 ps at 190 K. Such state can be trapped for tens of minutes at 7 K, showing that photo-induced polarization change can be realized in this system. These results directly demonstrate that a change in the molecular dipole moments induced by intramolecular electron transfer can introduce a macroscopic polarization change in VT compounds.
|
Apr 2020
|
|
I10-Beamline for Advanced Dichroism
|
Christoph
Klewe
,
Qian
Li
,
Mengmeng
Yang
,
Alpha T.
N’diaye
,
David M.
Burn
,
Thorsten
Hesjedal
,
Adriana
Figueroa
,
Chanyong
Hwang
,
Jia
Li
,
Robert J.
Hicken
,
Padraic
Shafer
,
Elke
Arenholz
,
Gerrit
Van Der Laan
,
Ziqiang
Qiu
Diamond Proposal Number(s):
[18542, 19116, 20483, 20493, 21616]
|
Apr 2020
|
|
I10-Beamline for Advanced Dichroism
|
M. T.
Birch
,
D.
Cortés-ortuño
,
L. A.
Turnbull
,
M. N.
Wilson
,
F.
Groß
,
N.
Träger
,
A.
Laurenson
,
N.
Bukin
,
S. H.
Moody
,
M.
Weigand
,
G.
Schütz
,
H.
Popescu
,
R.
Fan
,
P.
Steadman
,
J. A. T.
Verezhak
,
G.
Balakrishnan
,
J. C.
Loudon
,
A. C.
Twitchett-harrison
,
O.
Hovorka
,
H.
Fangohr
,
F. Y.
Ogrin
,
J.
Gräfe
,
P. D.
Hatton
Diamond Proposal Number(s):
[20866]
Open Access
Abstract: Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they are commonly portrayed as two dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the host material. The study of this skyrmion tube state (SkT) is vital for furthering the understanding of skyrmion formation and dynamics for future applications. However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure. The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigation into this unexplored dimension of the skyrmion spin texture.
|
Apr 2020
|
|
I09-Surface and Interface Structural Analysis
I10-Beamline for Advanced Dichroism
|
Georgios
Araizi-kanoutas
,
Jaap
Geessinck
,
Nicolas
Gauquelin
,
Steef
Smit
,
Xanthe H.
Verbeek
,
Shrawan K.
Mishra
,
Peter
Bencok
,
Christoph
Schlueter
,
Tien-lin
Lee
,
Dileep
Krishnan
,
Jarmo
Fatermans
,
Jo
Verbeeck
,
Guus
Rijnders
,
Gertjan
Koster
,
Mark S.
Golden
Abstract: We report charge transfer up to a single electron per interfacial unit cell across nonpolar heterointerfaces from the Mott insulator
LaTi
O
3
to the charge transfer insulator
LaCo
O
3
. In high-quality bi- and trilayer systems grown using pulsed laser deposition, soft x-ray absorption, dichroism, and scanning transmission electron microscopy-electron energy loss spectroscopy are used to probe the cobalt-
3
d
electron count and provide an element-specific investigation of the magnetic properties. The experiments show the cobalt valence conversion is active within 3 unit cells of the heterointerface, and able to generate full conversion to
3
d
7
divalent Co, which displays a paramagnetic ground state. The number of
LaTi
O
3
/
LaCo
O
3
interfaces, the thickness of an additional, electronically insulating “break” layer between the
LaTi
O
3
and
LaCo
O
3
, and the
LaCo
O
3
film thickness itself in trilayers provide a trio of control knobs for average charge of the cobalt ions in
LaCo
O
3
, illustrating the efficacy of
O
−
2
p
band alignment as a guiding principle for property design in complex oxide heterointerfaces.
|
Feb 2020
|
|
I06-Nanoscience
I10-Beamline for Advanced Dichroism
|
Yu
Yan
,
Xianyang
Lu
,
Bo
Liu
,
Xiaoqian
Zhang
,
Xiangyu
Zheng
,
Hao
Meng
,
Wenqing
Liu
,
Junlin
Wang
,
Iain G.
Will
,
Jing
Wu
,
Ping Kwan Johnny
Wong
,
Jianwang
Cai
,
Jun
Du
,
Rong
Zhang
,
Yongbing
Xu
Diamond Proposal Number(s):
[16538]
Abstract: Perpendicular magnetic anisotropy (PMA) in the Ta/CoFeB/MgO system has been studied using x-ray magnetic circular dichroism and vibrating sample magnetometry. The ratios of the orbital to spin magnetic moments of Co atoms in the Ta/CoFeB/MgO structures with PMA have been found to be enhanced by 100%, compared with the Ta/CoFeB/Ta structure without PMA. The orbital moments of Co are as large as
0.30
μ
B
0.30μB
, more than half of their spin moments in the perpendicularly magnetized Ta/CoFeB/MgO structures. The results indicate that the PMA observed in the CoFeB/MgO structures is related to the increased spin–orbital coupling of the Co atoms. This work offers experimental evidence of the correlation between PMA and the element-specific spin and orbital moments in the Ta/CoFeB/MgO systems.
|
Feb 2020
|
|
I10-Beamline for Advanced Dichroism
|
Peng
Chen
,
Yong
Zhang
,
Qi
Yao
,
Fugu
Tian
,
Lun
Li
,
Zhengkun
Qi
,
Xiaoyang
Liu
,
Liyang
Liao
,
Cheng
Song
,
Jingyuan
Wang
,
Jing
Xia
,
Gang
Li
,
David M.
Burn
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Shilei
Zhang
,
Xufeng
Kou
Diamond Proposal Number(s):
[21875, 23895]
Abstract: Engineering the anomalous Hall effect (AHE) is the key to manipulate the magnetic orders in the emerging magnetic topological insulators (MTIs). In this letter, we synthesize the epitaxial Bi2Te3/MnTe magnetic heterostructures and observe pronounced AHE signals from both layers combined together. The evolution of the resulting hybrid AHE intensity with the top Bi2Te3 layer thickness manifests the presence of an intrinsic ferromagnetic phase induced by the topological surface states at the heterolayer interface. More importantly, by doping the Bi2Te3 layer with Sb, we are able to manipulate the sign of the Berry phase-associated AHE component. Our results demonstrate the unparalleled advantages of MTI heterostructures over magnetically doped TI counterparts in which the tunability of the AHE response can be greatly enhanced. This in turn unveils a new avenue for MTI heterostructure-based multifunctional applications.
|
Feb 2020
|
|
