|
|
Dennis Valbjørn
Christensen
,
Urs
Staub
,
T. R.
Devidas
,
Beena
Kalisky
,
Katja
Nowack
,
James Luke
Webb
,
Ulrik L.
Andersen
,
Alexander
Huck
,
David Aaron
Broadway
,
Kai
Wagner
,
Patrick
Maletinsky
,
Toeno
Van Der Sar
,
Chunhui
Du
,
Amir
Yacoby
,
David
Collomb
,
Simon J.
Bending
,
Ahmet
Oral
,
Hans Josef
Hug
,
Andrada Oana
Mandru
,
Volker
Neu
,
Hans Werner
Schumacher
,
Sibylle
Sievers
,
Hitoshi
Saito
,
Alexander Ako
Khajetoorians
,
Nadine
Hauptmann
,
Susanne
Baumann
,
Alexander
Eichler
,
Christian
Degen
,
Jeffrey
Mccord
,
Michael
Vogel
,
Manfred
Fiebig
,
Peter
Fischer
,
Aurelio
Hierro-Rodriguez
,
Simone
Finizio
,
Sarnjeet
Dhesi
,
Claire
Donnelly
,
Felix
Buttner
,
Ofer
Kfir
,
Wen
Hu
,
Sergey
Zayko
,
Stefan
Eisebitt
,
Bastian
Pfau
,
Robert
Frömter
,
Mathias
Klaui
,
Fehmi
Yasin
,
Benjamin J.
Mcmorran
,
Shinichiro
Seki
,
Xiuzhen
Yu
,
Axel
Lubk
,
Daniel
Wolf
,
Nini
Pryds
,
Denys
Makarov
,
Martino
Poggio
Open Access
Abstract: Considering the growing interest in magnetic materials for unconventional computing, data storage, and sensor applications, there is active research not only on material synthesis but also characterisation of their properties. In addition to structural and integral magnetic characterisations, imaging of magnetization patterns, current distributions and magnetic fields at nano- and microscale is of major importance to understand the material responses and qualify them for specific applications. In this roadmap, we aim to cover a broad portfolio of techniques to perform nano- and microscale magnetic imaging using SQUIDs, spin center and Hall effect magnetometries, scanning probe microscopies, x-ray- and electron-based methods as well as magnetooptics and nanoMRI. The roadmap is aimed as a single access point of information for experts in the field as well as the young generation of students outlining prospects of the development of magnetic imaging technologies for the upcoming decade with a focus on physics, materials science, and chemistry of planar, 3D and geometrically curved objects of different material classes including 2D materials, complex oxides, semi-metals, multiferroics, skyrmions, antiferromagnets, frustrated magnets, magnetic molecules/nanoparticles, ionic conductors, superconductors, spintronic and spinorbitronic materials.
|
Mar 2024
|
|
I06-Nanoscience (XPEEM)
|
M.
Jourdan
,
S.
Reimers
,
Y.
Lytvynenko
,
Y. R.
Niu
,
E.
Golias
,
B.
Sarpi
,
L. S. I.
Veiga
,
T.
Denneulin
,
A.
Kovács
,
R. E.
Dunin-Borkowski
,
J.
Bläßer
,
M.
Klaui
Diamond Proposal Number(s):
[30141]
Abstract: Antiferromagnets (AFMs) are promising for future spintronic applications because of their fast dynamics and lack of stray fields. For the required switching of the Néel vector (staggered magnetization), a current induced bulk Néel spin-orbit torque (NSOT) is most promising. Here we demonstrate current pulse induced complete, remanent, and reversible Néel vector switching of epitaxial Mn2Au(001) thin films. A current polarity dependence demonstrates an NSOT acting on AFM domain walls. We correlate direct imaging of the Néel vector reorientation by x-ray photoemission electron microscopy with measurements of the associated anisotropic magnetoresistance [1].
|
Sep 2023
|
|
I06-Nanoscience (XPEEM)
|
C.
Schmitt
,
L.
Sanchez-Tejerina
,
M.
Filianina
,
F.
Fuhrmann
,
H.
Meer
,
R.
Ramos
,
F.
Maccherozzi
,
D.
Backes
,
E.
Saitoh
,
G.
Finocchio
,
L.
Baldrati
,
M.
Klaui
Diamond Proposal Number(s):
[22448]
Abstract: The understanding of antiferromagnetic domain walls, which are the interface between domains with different Néel order orientations, is a crucial aspect to enable the use of antiferromagnetic materials as active elements in future spintronic devices. In this work, we demonstrate that in antiferromagnetic NiO/Pt bilayers arbitrary-shaped structures can be generated by switching driven by electrical current pulses. The generated domains are T domains, separated from each other by a domain wall whose spins are pointing toward the average direction of the two T domains rather than the common axis of the two planes. Interestingly, this direction is the same for the whole domain wall indicating the absence of strong Lifshitz invariants. The domain wall can be micromagnetically modeled by strain distributions in the NiO thin film induced by the MgO substrate, deviating from the bulk anisotropy. From our measurements we determine the domain-wall width to have a full width at half maximum of
Δ
=
98
±
10
nm, demonstrating strong confinement.
|
May 2023
|
|
I06-Nanoscience (XPEEM)
|
S.
Reimers
,
Y.
Lytvynenko
,
Y. R.
Niu
,
E.
Golias
,
B.
Sarpi
,
L. S. I.
Veiga
,
T.
Denneulin
,
A.
Kovács
,
R. E.
Dunin-Borkowski
,
J.
Bläßer
,
M.
Klaui
,
M.
Jourdan
Diamond Proposal Number(s):
[30141]
Open Access
Abstract: Current pulse driven Néel vector rotation in metallic antiferromagnets is one of the most promising concepts in antiferromagnetic spintronics. We show microscopically that the Néel vector of epitaxial thin films of the prototypical compound Mn2Au can be reoriented reversibly in the complete area of cross shaped device structures using single current pulses. The resulting domain pattern with aligned staggered magnetization is long term stable enabling memory applications. We achieve this switching with low heating of ≈20 K, which is promising regarding fast and efficient devices without the need for thermal activation. Current polarity dependent reversible domain wall motion demonstrates a Néel spin-orbit torque acting on the domain walls.
|
Apr 2023
|
|
I06-Nanoscience (XPEEM)
|
S. P.
Bommanaboyena
,
D.
Backes
,
L. S. I.
Veiga
,
S. S.
Dhesi
,
Y. R.
Niu
,
B.
Sarpi
,
T.
Denneulin
,
A.
Kovács
,
T.
Mashoff
,
O.
Gomonay
,
J.
Sinova
,
K.
Everschor-Sitte
,
D.
Schönke
,
R. M.
Reeve
,
M.
Klaui
,
H.-J.
Elmers
,
M.
Jourdan
Diamond Proposal Number(s):
[29305]
Open Access
Abstract: In antiferromagnetic spintronics, the read-out of the staggered magnetization or Néel vector is the key obstacle to harnessing the ultra-fast dynamics and stability of antiferromagnets for novel devices. Here, we demonstrate strong exchange coupling of Mn2Au, a unique metallic antiferromagnet that exhibits Néel spin-orbit torques, with thin ferromagnetic Permalloy layers. This allows us to benefit from the well-established read-out methods of ferromagnets, while the essential advantages of antiferromagnetic spintronics are only slightly diminished. We show one-to-one imprinting of the antiferromagnetic on the ferromagnetic domain pattern. Conversely, alignment of the Permalloy magnetization reorients the Mn2Au Néel vector, an effect, which can be restricted to large magnetic fields by tuning the ferromagnetic layer thickness. To understand the origin of the strong coupling, we carry out high resolution electron microscopy imaging and we find that our growth yields an interface with a well-defined morphology that leads to the strong exchange coupling.
|
Nov 2021
|
|
I06-Nanoscience (XPEEM)
|
C.
Schmitt
,
L.
Baldrati
,
L.
Sanchez-Tejerina
,
F.
Schreiber
,
A.
Ross
,
M.
Filianina
,
S.
Ding
,
F.
Fuhrmann
,
R.
Ramos
,
F.
Maccherozzi
,
D.
Backes
,
M.-A.
Mawass
,
F.
Kronast
,
S.
Valencia
,
E.
Saitoh
,
G.
Finocchio
,
M.
Klaui
Diamond Proposal Number(s):
[22448]
Abstract: Understanding the electrical manipulation of the antiferromagnetic order is a crucial aspect to enable the design of antiferromagnetic devices working at THz frequencies. Focusing on collinear insulating antiferromagnetic
Ni
O
/
Pt
thin films as a materials platform, we identify the crystallographic orientation of the domains that can be switched by currents and quantify the Néel-vector direction changes. We demonstrate electrical switching between different T domains by current pulses, finding that the Néel-vector orientation in these domains is along [
±
5
±
5
19], different compared to the bulk
⟨
112
⟩
directions. The final state of the in-plane component of the Néel vector
n
IP
after switching by current pulses
j
along the
[
1
±
1
0
]
directions is
n
IP
∥
j
. By comparing the observed Néel-vector orientation and the strain in the thin films, assuming that this variation arises solely from magnetoelastic effects, we quantify the order of magnitude of the magnetoelastic coupling coefficient as
b
0
+
2
b
1
=
3
×
10
7
J
/
m
3
. This information is key for the understanding of current-induced switching in antiferromagnets and for the design and use of such devices as active elements in spintronic devices.
|
Mar 2021
|
|
I06-Nanoscience (XPEEM)
|
Diamond Proposal Number(s):
[23819]
Abstract: Tm
Fe
O
3
(TFO) is a canted antiferromagnet that undergoes a spin reorientation transition (SRT) with temperature between 82 and 94 K in single crystals. In this temperature region, the Néel vector continuously rotates from the crystallographic
c
axis (below 82 K) to the
a
axis (above 94 K). The SRT allows for a temperature control of distinct antiferromagnetic states without the need for a magnetic field, making it apt for applications working at terahertz frequencies. For device applications, thin films of TFO are required as well as an electrical technique for read-out of the magnetic state. Here, we demonstrate that orthorhombic TFO thin films can be grown by pulsed laser deposition and the detection of the SRT in TFO thin films can be accessed by making use of the all-electrical spin Hall magnetoresistance, in good agreement for the temperature range where the SRT occurs in bulk crystals. Our results demonstrate that one can electrically detect the SRT in insulators.
|
Jan 2021
|
|
I06-Nanoscience (XPEEM)
|
Andrew
Ross
,
Romain
Lebrun
,
Lorenzo
Baldrati
,
Akashdeep
Kamra
,
Olena
Gomonay
,
Shilei
Ding
,
Felix
Schreiber
,
Dirk
Backes
,
Francesco
Maccherozzi
,
Daniel A.
Grave
,
Avner
Rothschild
,
Jairo
Sinova
,
Mathias
Klaui
Diamond Proposal Number(s):
[23819]
Abstract: We report room-temperature long-distance spin transport of magnons in antiferromagnetic thin-film hematite doped with Zn. The additional dopants significantly alter the magnetic anisotropies, resulting in a complex equilibrium spin structure that is capable of efficiently transporting spin angular momentum at room temperature without the need for a well-defined, pure easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion lengths of up to 1.5 μm, and magnetic domain governed decay lengths of 175 nm for the low-frequency magnons, through electrical transport measurements demonstrating that the introduction of nonmagnetic dopants does not strongly reduce the transport length scale, showing that the magnetic damping of hematite is not significantly increased. We observe a complex field dependence of the nonlocal signal independent of the magnetic state visible, in the local magnetoresistance and direct magnetic imaging of the antiferromagnetic domain structure. We explain our results in terms of a varying and applied field-dependent ellipticity of the magnon modes reaching the detector electrode allowing us to tune the spin transport.
|
Dec 2020
|
|
I06-Nanoscience (XPEEM)
|
Diamond Proposal Number(s):
[20534]
Abstract: The effects of current induced Néel spin-orbit torques on the antiferromagnetic domain structure of epitaxial Mn2Au thin films were investigated by x-ray magnetic linear dichroism–photoemission electron microscopy.We observed current induced switching of antiferromagnetic domains essentially corresponding to morphological features of the samples. Reversible as well as irreversible Néel vector reorientation was obtained in different parts of the samples and the switching of up to 30% of all domains in the field of view of 10 μm is demonstrated. Our direct microscopical observations are compared to and fully consistent with anisotropic magnetoresistance
effects previously attributed to current induced Néel vector switching in Mn2Au.
|
Apr 2019
|
|
I06-Nanoscience (XPEEM)
|
Diamond Proposal Number(s):
[17120]
Abstract: In the field of antiferromagnetic (AFM) spintronics, information about the Néel vector, AFM domain sizes,
and spin-flop fields is a prerequisite for device applications but is not available easily.We have investigated AFM domains and spin-flop-induced changes of domain patterns in Mn2Au(001) epitaxial thin films by x-ray magnetic linear dichroism photoemission electron microscopy (PEEM) using magnetic fields up to 70 T. As-prepared Mn2Au films exhibit AFM domains with an average size of 1μm. Application of a 30 T field, exceeding the spin-flop field, along a magnetocrystalline easy axis dramatically increases the AFM domain size with Néel vectors perpendicular to the applied field direction. The width of Néel-type domain walls (DW) is below the
spatial resolution of the PEEM and therefore can only be estimated from an analysis of the DW profile to be smaller than 80 nm. Furthermore, using the values for the DW width and the spin-flop field, we evaluate an in-plane anisotropy constant ranging between 1 and 17 eV/f.u..
|
Apr 2018
|
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