I09-Surface and Interface Structural Analysis
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Prajwal M.
Laxmeesha
,
Rajesh
Dutta
,
Rajeev Kumar
Rai
,
Sharup
Sheikh
,
Michael F.
Discala
,
Uditha M.
Jayathilake
,
Alexander
Velič
,
Tarush
Tandon
,
Tessa D.
Tucker
,
Christoph
Klewe
,
Haile
Ambaye
,
Timothy
Charlton
,
Tien-Lin
Lee
,
Eric A.
Stach
,
Kemp W.
Plumb
,
Alexander X.
Gray
,
Steven J.
May
Diamond Proposal Number(s):
[40454]
Abstract: Kagome metals are an intriguing class of quantum materials as the presence of both flat bands and Dirac points provides access to functional properties present in strongly correlated and topological materials. To fully harness these electronic features, the ability to tune the Fermi level relative to the band positions is needed. Here, we explore the structural, electronic, and magnetic impacts of substitutional alloying within ferromagnetic kagome metal Fe3Sn2 in thin films grown by molecular beam epitaxy. Transition metals, Mn and Co, are chosen as substitutes for Fe to reduce or increase the d-band electron count, thereby moving the Fermi level accordingly. We find that Co is not incorporated into the Fe3Sn2 structure but instead results in a two-phase Fe–Co and (Fe,Co)Sn composite. In contrast, Fe3−xMnxSn2 films are realized with x of up to 1.0, retaining crystalline quality comparable with the parent phase. The incorporation of Mn repositions the flat bands relative to the Fermi level in a manner consistent with hole-doping, as revealed by hard x-ray photoemission and density functional theory. The Fe3−xMnxSn2 films retain room temperature ferromagnetism, with x-ray magnetic circular dichroism measurements confirming that the Fe and Mn moments are ferromagnetically aligned. The ability to hole-dope this magnetic kagome metal provides a platform for tuning properties, such as anomalous Hall and Nernst responses.
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Jan 2026
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I10-Beamline for Advanced Dichroism - scattering
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Connor
Sait
,
Maciej
Dabrowski
,
Jade N.
Scott
,
William R.
Hendren
,
David G.
Newman
,
Alpha T.
N'Diaye
,
Christoph
Klewe
,
Padraic
Shafer
,
Gerrit
Van Der Laan
,
Paul S.
Keatley
,
Robert
Bowman
,
Robert J.
Hicken
Diamond Proposal Number(s):
[30343]
Open Access
Abstract: Nickel-platinum-based synthetic ferrimagnets (SFi's) are highly tunable and rare-earth-free materials that allow ultrafast all optical control of magnetism to be explored. This study considers a SFi composed of a ferromagnetic [Ni/Pt] multilayer and a ferromagnetic Co layer, separated by an Ir layer that mediates an antiferromagnetic coupling. Helicity-independent all optical switching (HI-AOS) between two antiparallel magnetization states is observed. AOS may be realized at increased temperature through reduction of the thickness of the Pt layers. Switching is unidirectional and has a strong dependence on the applied magnetic field history, which suggests the possible presence of a nanoscale magnetic texture that may be important in controlling AOS in SFi systems.
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Apr 2024
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I10-Beamline for Advanced Dichroism - scattering
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Margaret R.
Mccarter
,
Kook Tae
Kim
,
Vladimir A.
Stoica
,
Sujit
Das
,
Christoph
Klewe
,
Elizabeth P.
Donoway
,
David M.
Burn
,
Padraic
Shafer
,
Fanny
Rodolakis
,
Mauro A. p.
Gonçalves
,
Fernando
Gómez-Ortiz
,
Jorge
Íñiguez
,
Pablo
García-Fernández
,
Javier
Junquera
,
Stephen W.
Lovesey
,
Gerrit
Van Der Laan
,
Se Young
Park
,
John W.
Freeland
,
Lane W.
Martin
,
Dong Ryeol
Lee
,
Ramamoorthy
Ramesh
Diamond Proposal Number(s):
[24797]
Abstract: An escalating challenge in condensed-matter research is the characterization of emergent order-parameter nanostructures such as ferroelectric and ferromagnetic skyrmions. Their small length scales coupled with complex, three-dimensional polarization or spin structures makes them demanding to trace out fully. Resonant elastic x-ray scattering (REXS) has emerged as a technique to study chirality in spin textures such as skyrmions and domain walls. It has, however, been used to a considerably lesser extent to study analogous features in ferroelectrics. Here, we present a framework for modeling REXS from an arbitrary arrangement of charge quadrupole moments, which can be applied to nanostructures in materials such as ferroelectrics. With this, we demonstrate how extended reciprocal space scans using REXS with circularly polarized x rays can probe the three-dimensional structure and chirality of polar skyrmions. Measurements, bolstered by quantitative scattering calculations, show that polar skyrmions of mixed chirality coexist, and that REXS allows valuation of relative fractions of right- and left-handed skyrmions. Our quantitative analysis of the structure and chirality of polar skyrmions highlights the capability of REXS for establishing complex topological structures toward future application exploits.
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Dec 2022
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I10-Beamline for Advanced Dichroism - scattering
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Kook Tae
Kim
,
Margaret R.
Mccarter
,
Vladimir A.
Stoica
,
Sujit
Das
,
Christoph
Klewe
,
Elizabeth P.
Donoway
,
David M.
Burn
,
Padraic
Shafer
,
Fanny
Rodolakis
,
Mauro A. P.
Gonçalves
,
Fernando
Gómez-Ortiz
,
Jorge
Íñiguez
,
Pablo
García-Fernández
,
Javier
Junquera
,
Sandhya
Susarla
,
Stephen W.
Lovesey
,
Gerrit
Van Der Laan
,
Se Young
Park
,
Lane W.
Martin
,
John W.
Freeland
,
Ramamoorthy
Ramesh
,
Dong Ryeol
Lee
Diamond Proposal Number(s):
[24797]
Open Access
Abstract: Resonant elastic X-ray scattering (REXS) offers a unique tool to investigate solid-state systems providing spatial knowledge from diffraction combined with electronic information through the enhanced absorption process, allowing the probing of magnetic, charge, spin, and orbital degrees of spatial order together with electronic structure. A new promising application of REXS is to elucidate the chiral structure of electrical polarization emergent in a ferroelectric oxide superlattice in which the polarization vectors in the REXS amplitude are implicitly described through an anisotropic tensor corresponding to the quadrupole moment. Here, we present a detailed theoretical framework and analysis to quantitatively analyze the experimental results of Ti L-edge REXS of a polar vortex array formed in a PbTiO3/SrTiO3 superlattice. Based on this theoretical framework, REXS for polar chiral structures can become a useful tool similar to x-ray resonant magnetic scattering (XRMS), enabling a comprehensive study of both electric and magnetic REXS on the chiral structures.
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Apr 2022
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Open Access
Abstract: Ferromagnetic resonance (FMR) and x-ray detected FMR (XFMR) results for Permalloy (Py) and [Co/Pt]10/Py films, with and without thin Pt spacers between the [Co/Pt]10 and Py layers, are presented and discussed. The first layer [Co/Pt]10 was chosen due its characteristic perpendicular anisotropy, with the potential to pin neighboring Py spins. However, in practice, the FMR results were found to be dominated by the 50-nm-thick Py films, especially when the thickness of the Pt spacer exceeds 1.5 nm. Nonetheless, out-of-plane FMR measurements reveal interesting behavior. In particular, the uniform k=0 mode is extremely sensitive to the alignment of the magnetic field normal to the film. Misalignment by just 3° shifts the cusp, at Bappz ~ μ0M in the plot of resonance frequency against applied field, upwards to ~ 6 GHz. In addition, out-of-plane VNA-FMR maps reveal the presence of additional modes. For example, a perpendicular standing spin-wave (PSSW)-state, above the cusp at Bappz ≥ μ0M, is clearly identified. However, as the magnetic field is reduced below the cusp, the PSSW state morphs, continuously, through a series of canted spin-wave states (CSSW) into a horizontal standing spin-wave (HSSW) state, increasing in frequency to ~ 9.5 GHz. Finally, the PSSW, CSSW and HSSW states, are accurately interpreted, using a multi-layer model of the Py film.
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Jan 2021
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I16-Materials and Magnetism
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Stephan
Geprags
,
Christoph
Klewe
,
Sibylle
Meyer
,
Dominik
Graulich
,
Felix
Schade
,
Marc
Schneider
,
Sonia
Francoual
,
Stephen P.
Collins
,
Katharina
Ollefs
,
Fabrice
Wilhelm
,
Andrei
Rogalev
,
Yves
Joly
,
Sebastian T. B.
Goennenwein
,
Matthias
Opel
,
Timo
Kuschel
,
Rudolf
Gross
Diamond Proposal Number(s):
[12772]
Abstract: The magnetic state of heavy metal Pt thin films in proximity to the ferrimagnetic insulator
Y
3
Fe
5
O
12
has been investigated systematically by means of x-ray magnetic circular dichroism and x-ray resonant magnetic reflectivity measurements combined with angle-dependent magnetotransport studies. To reveal intermixing effects as the possible cause for induced magnetic moments in Pt, we compare thin film heterostructures with different orders of the layer stacking and different interface properties. For standard Pt layers on
Y
3
Fe
5
O
12
thin films, we do not detect any static magnetic polarization in Pt. These samples show an angle-dependent magnetoresistance behavior, which is consistent with the established spin Hall magnetoresistance. In contrast, for the inverted layer sequence,
Y
3
Fe
5
O
12
thin films grown on Pt layers, Pt displays a finite induced magnetic moment comparable to that of all-metallic Pt/Fe bilayers. This magnetic moment is found to originate from finite intermixing at the
Y
3
Fe
5
O
12
/
Pt
interface. As a consequence, we found a complex angle-dependent magnetoresistance indicating a superposition of the spin Hall and the anisotropic magnetoresistance in these types of samples. Both effects can be disentangled from each other due to their different angle dependence and their characteristic temperature evolution.
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Dec 2020
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I10-Beamline for Advanced Dichroism - scattering
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Maciej
Dabrowski
,
Andreas
Frisk
,
David M.
Burn
,
David G.
Newman
,
Christoph
Klewe
,
Alpha T.
N’diaye
,
Padraic
Shafer
,
Elke
Arenholz
,
Graham J.
Bowden
,
Thorsten
Hesjedal
,
Gerrit
Van Der Laan
,
Gino
Hrkac
,
Robert J.
Hicken
Diamond Proposal Number(s):
[17745, 19116, 20760]
Abstract: Microwave and heat-assisted magnetic recordings are two competing technologies that have greatly increased the capacity of hard disk drives. The efficiency of the magnetic recording process can be further improved by employing non-collinear spin structures that combine perpendicular and in-plane magnetic anisotropy. Here, we investigate both microwave and optically excited magnetization dynamics in [Co/Pt]/NiFe exchange spring samples. The resulting canted magnetization within the nanoscale [Co/Pt]/NiFe interfacial region allows for optically stimulated magnetization precession to be observed for an extended magnetic field and frequency range. The results can be explained by formation of an imprinted domain structure, which locks the magnetization orientation and makes the structures more robust against external perturbations. Tuning the canted interfacial domain structure may provide greater control of optically excited magnetization reversal and optically generated spin currents, which are of paramount importance for future ultrafast magnetic recording and spintronic applications.
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Nov 2020
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I10-Beamline for Advanced Dichroism - scattering
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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.
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May 2020
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I10-Beamline for Advanced Dichroism - scattering
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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]
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Apr 2020
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I06-Nanoscience (XPEEM)
I10-Beamline for Advanced Dichroism - scattering
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C. J.
Durrant
,
L. R.
Shelford
,
R. A. J.
Valkass
,
R. J.
Hicken
,
A. I.
Figueroa
,
A. A.
Baker
,
G.
Van Der Laan
,
L. B.
Duffy
,
P.
Shafer
,
C.
Klewe
,
E.
Arenholz
,
S. A.
Cavill
,
J. R.
Childress
,
J. A.
Katine
Diamond Proposal Number(s):
[8782, 11585]
Abstract: Spin pumping has been studied within Ta / Ag / Ni81Fe19 (0–5 nm) / Ag (6 nm) / Co2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni81Fe19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNAFMR)
experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfer torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and super-paramagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR line width that we attribute to improved interface quality. This study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.
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Oct 2017
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