I10-Beamline for Advanced Dichroism - scattering
|
Bin
He
,
Haonan
Jin
,
Dongfeng
Zheng
,
Yizhou
Liu
,
Jialiang
Li
,
Yue
Hu
,
Yuqiang
Wang
,
Junwei
Zhang
,
Yong
Peng
,
Caihua
Wan
,
Tao
Zhu
,
Xiufeng
Han
,
Shilei
Zhang
,
Guoqiang
Yu
Diamond Proposal Number(s):
[27692]
Abstract: Antiferromagnetic (AFM) skyrmions are magnetic vortices composed of antiparallell-aligned neighboring spins. In stark contrast to conventional skyrmions based on ferromagnetic order, AFM skyrmions have vanished stray fields, higher response frequencies, and rectified translational motion driven by an external force. Therefore, AFM skyrmions promise highly efficient spintronics devices with high bit mobility and density. Nevertheless, the experimental realization of intrinsic AFM skyrmions remains elusive. Here, we show that AFM skyrmions can be nucleated via interfacial exchange coupling at the surface of a room-temperature AFM material, IrMn, exploiting the particular response from uncompensated moments to the thermal annealing and imprinting effects. Further systematic magnetic characterizations validate the existence of such an AFM order at the IrMn/CoFeB interfaces. Such AFM skyrmions have a typical size of 100 nm, which presents pronounced robustness against field and temperature. Our work opens new pathways for magnetic topological devices based on AFM skyrmions.
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Feb 2024
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I06-Nanoscience (XPEEM)
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Xinqi
Liu
,
Puyang
Huang
,
Yunyouyou
Xia
,
Lei
Gao
,
Liyang
Liao
,
Baoshan
Cui
,
Dirk
Backes
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Yuchen
Ji
,
Peng
Chen
,
Yifan
Zhang
,
Fan
Wu
,
Meixiao
Wang
,
Junwei
Zhang
,
Guoqiang
Yu
,
Cheng
Song
,
Yulin
Chen
,
Zhongkai
Liu
,
Yumeng
Yang
,
Yong
Peng
,
Gang
Li
,
Qi
Yao
,
Xufeng
Kou
Abstract: To harness the intriguing properties of 2D van der Waals (vdW) ferromagnets (FMs) for versatile applications, the key challenge lies in the reliable material synthesis for scalable device production. Here, the epitaxial growth of single-crystalline 1T-CrTe2 thin films on 2-inch sapphire substrates are demonstrated. Benefiting from the uniform surface energy of the dangling bond-free Al2O3(0001) surface, the layer-by-layer vdW growth mode is observed right from the initial growth stage, which warrants precise control of the sample thickness beyond three monolayer and homogeneous surface morphology across the entire wafer. Moreover, the presence of the Coulomb interaction at the CrTe2/Al2O3 interface plays an important role in tailoring the anomalous Hall response, and the structural optimization of the CrTe2-based spin-orbit torque device leads to a substantial switching power reduction by 54%. The results may lay out a general framework for the design of energy-efficient spintronics based on configurable vdW FMs.
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Sep 2023
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I10-Beamline for Advanced Dichroism - scattering
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Haonan
Jin
,
Wancong
Tan
,
Yizhou
Liu
,
Kejing
Ran
,
Raymond
Fan
,
Yanyan
Shangguan
,
Yao
Guang
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Jinsheng
Wen
,
Guoqiang
Yu
,
Shilei
Zhang
Diamond Proposal Number(s):
[27692, 28933, 30749]
Open Access
Abstract: Topological defects are fundamental concepts in physics, but little is known about the transition between distinct types across different dimensionalities. In topological magnetism, as in field theory, the transition between 1D strings and 0D monopoles is a key process whose observation has remained elusive. Here, we introduce a novel mechanism that allows for the controlled stabilization of emergent monopoles and show that magnetic skyrmion strings can be folded into monopoles. Conversely, they act as seeds out of which the entire string structure can unfold, containing its complete information. In chiral magnets, this process can be observed by resonant elastic X-ray scattering when the objects are in proximity to a polarized ferromagnet, whereby a pure monopole lattice is emerging on the surface. Our experimental proof of the reversible evolution from monopole to string sheds new light on topological defects and establishes the emergent monopole lattice as a new 3D topological phase.
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Jun 2023
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I10-Beamline for Advanced Dichroism - scattering
|
Peng
Chen
,
Qi
Yao
,
Junqi
Xu
,
Qiang
Sun
,
Alexander J.
Grutter
,
Patrick
Quarterman
,
Purnima P.
Balakrishnan
,
Christy J.
Kinane
,
Andrew J.
Caruana
,
Sean
Langridge
,
Ang
Li
,
Barat
Achinuq
,
Emily
Heppell
,
Yuchen
Ji
,
Shanshan
Liu
,
Baoshan
Cui
,
Jiuming
Liu
,
Puyang
Huang
,
Zhongkai
Liu
,
Guoqiang
Yu
,
Faxian
Xiu
,
Thorsten
Hesjedal
,
Jin
Zou
,
Xiaodong
Han
,
Haijun
Zhang
,
Yumeng
Yang
,
Xufeng
Kou
Diamond Proposal Number(s):
[30262]
Abstract: The intrinsic magnetic topological insulator MnBi2Te4 (MBT) provides a platform for the creation of exotic quantum phenomena. Novel properties can be created by modification of the MnBi2Te4 framework, but the design of stable magnetic structures remains challenging. Here we report ferromagnet-intercalated MnBi2Te4 superlattices with tunable magnetic exchange interactions. Using molecular beam epitaxy, we intercalate ferromagnetic MnTe layers into MnBi2Te4 to create [(MBT)(MnTe)m]N superlattices and examine their magnetic interaction properties using polarized neutron reflectometry and magnetoresistance measurements. Incorporation of the ferromagnetic spacer tunes the antiferromagnetic interlayer coupling of the MnBi2Te4 layers through the exchange-spring effect at MnBi2Te4/MnTe hetero-interfaces. The MnTe thickness can be used to modulate the relative strengths of the ferromagnetic and antiferromagnetic order, and the superlattice periodicity can tailor the spin configurations of the synthesized multilayers.
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Dec 2022
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I10-Beamline for Advanced Dichroism - scattering
|
Diamond Proposal Number(s):
[26148]
Open Access
Abstract: A major challenge in topological magnetism lies in the three-dimensional (3D) exploration of their magnetic textures. A recent focus has been the question of how 2D skyrmion sheets vertically stack to form distinct types of 3D topological strings. Being able to manipulate the vertical coupling should therefore provide a route to the engineering of topological states. Here, we present a new type of axially bound magnetic skyrmion string state in which the strings in two distinct materials are glued together across their interface. With quasi-tomographic resonant elastic X-ray scattering, the 3D skyrmion profiles before and after their binding across the interface were unambiguously determined and compared. Their attractive binding is accompanied by repulsive twisting; i.e., the coupled skyrmions mutually affect each other via a compensating twisting. This state exists in chiral magnet–magnetic thin film heterostructures, providing a new arena for the engineering of 3D topological phases.
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Apr 2022
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I10-Beamline for Advanced Dichroism - scattering
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Yao
Guang
,
Kejing
Ran
,
Junwei
Zhang
,
Yizhou
Liu
,
Senfu
Zhang
,
Xuepeng
Qiu
,
Yong
Peng
,
Xixiang
Zhang
,
Markus
Weigand
,
Joachim
Gräfe
,
Gisela
Schütz
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Shilei
Zhang
,
Guoqiang
Yu
,
Xiufeng
Han
Diamond Proposal Number(s):
[23785]
Abstract: A three-dimensional singular point that consists of two oppositely aligned emergent monopoles is identified in continuous CoTb thin films, as confirmed by complementary techniques of resonant elastic x-ray scattering, Lorentz transmission electron microscopy, and scanning transmission x-ray microscopy. This new type of topological defect can be regarded as a superposition of an emergent magnetic monopole and an antimonopole, around which the source and drain of the magnetic flux overlap in space. We experimentally prove that the observed spin twist seen in Lorentz transmission electron microscopy reveals the cross section of the superimposed three-dimensional structure, providing a straightforward strategy for the observation of magnetic singularities. Such a quasiparticle provides an excellent platform for studying the rich physics of emergent electromagnetism.
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Nov 2021
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I10-Beamline for Advanced Dichroism - scattering
|
Diamond Proposal Number(s):
[20182]
Open Access
Abstract: A chiral bobber is a localized three-dimensional magnetization configuration, terminated by a singularity. Chiral bobbers coexist with magnetic skyrmions in chiral magnets, lending themselves to new types of skyrmion-complementary bits of information. However, the on-demand creation of bobbers, as well as their direct observation remained elusive. Here, we introduce a new mechanism for creating a stable chiral bobber lattice state via the proximity of two skyrmion species with comparable size. This effect is experimentally demonstrated in a
Cu
2
OSeO
3
/
[
Ta
/
CoFeB
/
MgO
]
4
heterostructure in which an exotic bobber lattice state emerges in the phase diagram of
Cu
2
OSeO
3
. To unambiguously reveal the existence of the chiral bobber lattice state, we have developed a novel characterization technique, magnetic truncation rod analysis, which is based on resonant elastic x-ray scattering.
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Jan 2021
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I10-Beamline for Advanced Dichroism - scattering
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Yao
Guang
,
Yong
Peng
,
Zhengren
Yan
,
Yizhou
Liu
,
Junwei
Zhang
,
Xue
Zeng
,
Senfu
Zhang
,
Shilei
Zhang
,
David M.
Burn
,
Nicolas
Jaouen
,
Jinwu
Wei
,
Hongjun
Xu
,
Jiafeng
Feng
,
Chi
Fang
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Baoshan
Cui
,
Xixiang
Zhang
,
Guoqiang
Yu
,
Xiufeng
Han
Diamond Proposal Number(s):
[20183, 21868]
Abstract: The emergence of magnetic skyrmions, topological spin textures, has aroused tremendous interest in studying the rich physics related to their topology. While skyrmions promise high‐density and energy‐efficient magnetic memory devices for information technology, the manifestation of their nontrivial topology through single skyrmions and ordered and disordered skyrmion lattices could also give rise to many fascinating physical phenomena, such as chiral magnon and skyrmion glass states. Therefore, generating skyrmions at designated locations on a large scale, while controlling the skyrmion patterns, is the key to advancing topological magnetism. Here, a new, yet general, approach to the “printing” of skyrmions with zero‐field stability in arbitrary patterns on a massive scale in exchange‐biased magnetic multilayers is presented. By exploiting the fact that the antiferromagnetic order can be reconfigured by local thermal excitations, a focused electron beam with a graphic pattern generator to “print” skyrmions is used, which is referred to as skyrmion lithography. This work provides a route to design arbitrary skyrmion patterns, thereby establishing the foundation for further exploration of topological magnetism.
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Aug 2020
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I10-Beamline for Advanced Dichroism - scattering
|
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]
Open Access
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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