E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[23285]
Abstract: The ability to control the in-plane magnetic anisotropy of a thin film is important for magnetic device applications. One way of accomplishing this task is by glancing angle deposition (GLAD). In this study, thin Co layers have been deposited using GLAD magnetron sputtering on MgO(001) and MgO(110) substrates. For Co films on MgO(001), the in-plane anisotropy direction can be directly controlled via the deposition angle. In contrast, for Co on MgO(110), the anisotropy due to the deposition angle is competing with the anisotropy induced by the substrate, while the growth parameters determine which contribution dominates. On the other hand, while on MgO(001) the deposition angle as well as the film thickness affect the strength of the Co in-plane anisotropy, no influence of these parameters on the magnetic properties is found for films on MgO(110).
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Mar 2023
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I15-Extreme Conditions
I19-Small Molecule Single Crystal Diffraction
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David M.
Jarvis
,
Matthew J.
Coak
,
Hayrullo
Hamidov
,
Charles R. S.
Haines
,
Giulio I.
Lampronti
,
Cheng
Liu
,
Shiyu
Deng
,
Dominik
Daisenberger
,
David R.
Allan
,
Mark R.
Warren
,
Andrew R.
Wildes
,
Siddharth S.
Saxena
Diamond Proposal Number(s):
[15949, 23524]
Abstract: FePS
3
is a layered magnetic van der Waals compound that undergoes a Mott insulator-metal transition under applied pressure. The transition has an associated change in the crystal symmetry and magnetic structure. Understanding the underlying physics of these transitions requires a detailed understanding of the crystal structure as a function of pressure. Two conflicting models have previously been proposed for the evolution of the structure with pressure. To settle the disagreement, we present a study of the pressure-dependent crystal structures using both single-crystal and powder x-ray diffraction measurements. We show unambiguously that the highest-pressure transition involves a collapse of the interplanar spacing, along with an increase in symmetry from a monoclinic to a trigonal space group, to the exclusion of other models. Our collected results are crucial for understanding high-pressure behavior in these materials and demonstrate a clear and complete methodology for exploring complex two-dimensional material structures under pressure.
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Feb 2023
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I10-Beamline for Advanced Dichroism
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Xiaodong
Xie
,
Kejing
Ran
,
Yizhou
Liu
,
Raymond
Fan
,
Wancong
Tan
,
Haonan
Jin
,
Manuel
Valvidares
,
Nicolas
Jaouen
,
Haifeng
Du
,
Gerrit
Van Der Laan
,
Thorsten
Hesjedal
,
Shilei
Zhang
Diamond Proposal Number(s):
[20437, 26148, 22629]
Abstract: We identify a three-dimensional skyrmion side-face state in chiral magnets that consists of a thin layer of modulated surface spirals and an array of phase-locked skyrmion screws. Such chiral spin structures lead to a characteristic X-shaped magnetic diffraction pattern in resonant elastic x-ray scattering, reminiscent of Photo 51 of the DNA double-helix diffraction. By measuring both thin plates and bulk
Cu
2
OSeO
3
crystals in the field-in-plane geometry, we unambiguously identify the modulated skyrmion strings by retrieving their chirality and helix angle. The breaking of the translational symmetry along the side faces suppresses the bulk-favored conical state, providing a stabilization mechanism for the skyrmion lattice phase that has been overlooked so far.
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Feb 2023
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I06-Nanoscience
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Diamond Proposal Number(s):
[14135]
Abstract: The size of the orbital moment in
Fe
3
O
4
has been the subject of a long-standing and contentious debate. In this paper, we make use of ferromagnetic resonance (FMR) spectroscopy and x-ray magnetic circular dichroism (XMCD) to provide complementary determinations of the size of the orbital moment in “bulklike” epitaxial
Fe
3
O
4
films grown on yttria-stabilized zirconia (111) substrates. Annealing the 100 nm as-grown films to
1100
∘
C
in a reducing atmosphere improves the stoichiometry and microstructure of the films, allowing for bulklike properties to be recovered as evidenced by x-ray diffraction and vibrating sample magnetometry. In addition, in-plane angular FMR spectra exhibit a crossover from a fourfold symmetry to the expected sixfold symmetry of the (111) surface, together with an anomalous peak in the FMR linewidth at
∼
10
GHz; this is indicative of low Gilbert damping in combination with two-magnon scattering. For the bulklike annealed sample, a spectroscopic splitting factor
g
≈
2.18
is obtained using both FMR and XMCD techniques, providing evidence for the presence of a finite orbital moment in
Fe
3
O
4
.
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Feb 2023
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I05-ARPES
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Hongwei
Fang
,
Meng
Lyu
,
Hao
Su
,
Jian
Yuan
,
Yiwei
Li
,
Lixuan
Xu
,
Shuai
Liu
,
Liyang
Wei
,
Xinqi
Liu
,
Haifeng
Yang
,
Qi
Yao
,
Meixiao
Wang
,
Yanfeng
Guo
,
Wujun
Shi
,
Yulin
Chen
,
Enke
Liu
,
Zhongkai
Liu
Abstract: The kagome-lattice crystal hosts various intriguing properties including the frustrated magnetism, charge order, topological state, superconductivity and correlated phenomena. To achieve high-performance kagome-lattice compounds for electronic and spintronic applications, careful tuning of the band structure would be desired. Here, the electronic structures of kagome-lattice crystal Ni3In2S2 were investigated by transport measurements, angle-resolved photoemission spectroscopy as well as ab initio calculations. The transport measurements reveal Ni3In2S2 as a compensated semimetal with record-high carrier mobility (∼8683 and 7356 cm2 V−1 S−1 for holes and electrons) and extreme magnetoresistance (15,518% at 2 K and 13 T) among kagome-lattice materials. These extraordinary properties are well explained by its band structure with indirect gap, small electron/hole pockets and large bandwidth of the 3d electrons of Ni on the kagome lattice. This work demonstrates that the crystal field and doping serve as the key tuning knobs to optimize the transport properties in kagome-lattice crystals. Our work provides material basis and optimization routes for kagome-lattice semimetals towards electronics and spintronics applications.
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Feb 2023
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I11-High Resolution Powder Diffraction
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Abstract: A high-resolution synchrotron X-ray diffraction study of a single-crystal YCrO3 compound was employed to obtain its crystallographic information, such as lattice parameters, atomic positions, bond lengths and angles, and local crystalline distortion size and mode. The measurements were taken at 120 K (below the antiferromagnetic transition temperature TN ≃ 141.5 K), 300 K (between TN and the ferroelectric transition temperature TC ≃ 473 K) and 500 K (above TC). Using the high intensity of synchrotron X-rays, it was possible to refine collected patterns with the previously proposed noncentrosymmetric monoclinic structural model (P1211, No. 4) and determine detailed structural parameters. Meanwhile, for a controlled study, the data were refined with the centrosymmetric orthorhombic space group (Pmnb, No. 62). The lattice constants a, b and c and the unit-cell volume increased nearly linearly upon heating. With the P1211 space group, the distributions of bond lengths and angles, as well as local distortion strengths, were observed to be more dispersed. This implies that (i) the local distortion mode of Cr2O6 at 120 K correlates with the formation of canted antiferromagnetic order by Cr1–Cr2 spin interactions, primarily via intermediate O3 and O4 ions; and (ii) the previously reported dielectric anomaly may have a microscopic origin in the strain-balanced Cr1—O3(O4) and Cr2—O5(O6) bonds as well as the local distortion modes of Cr1O6 and Cr2O6 octahedra at 300 K. Local crystalline distortion is shown to be an important factor in the formation of ferroelectric order. The comprehensive set of crystallographic information reported here allows for a complete understanding of the unique magnetic and ferroelectric properties of YCrO3.
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Dec 2022
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I10-Beamline for Advanced Dichroism
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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
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Diamond Proposal Number(s):
[23784]
Open Access
Abstract: Magnetic skyrmions (skyrmions hereafter) are magnetization configurations, whose topological robustness and nanoscale size have led to speculation that they could find use as a next-generation information carrier. Skyrmions have been observed in magnetic multilayer materials that are thin compared to the radius of a skyrmion, and chiral cubic single crystals that can be far larger than any characteristic skyrmion scale. In these single crystals, one would expect that skyrmions could exhibit interesting three-dimensional (3D) characteristics. Here, the symmetry of the micromagnetic free energy is investigated. This symmetry permits a complex 3D modulation of a skyrmion string, which we show to be a requirement of a skyrmion coexisting with the conical state. We discuss the implications of this modulation with respect to Thiele's equation and interskyrmion interactions. Further to this internal modulation, we study theoretically and show experimentally that the strings themselves must contort towards the surfaces of their confining crystals.
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Dec 2022
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Abstract: The Bragg diffraction of neutrons and x rays are well suited to the task of determining the distribution of magnetization in crystals. Applications of the two techniques proceed by contrasting observed intensities with intensities calculated with a specific model, and changing the model as need be to achieve satisfactory agreement. An all-in–all-out (AIAO) magnetic configuration of magnetic dipoles on a cubic face-centered lattice with networks of corner-sharing tetrahedra is often mentioned in the context of pyrochlore oxides, for example, but the corresponding neutron and x-ray-diffraction patterns appear to not have been calculated. Our results for patterns of Bragg spots from an AIAO magnetic configuration defined by a magnetic space group are symmetry informed and yield exact reflection conditions. Specifically, a long-range order of magnetic dipoles is forbidden in our model. Bulk properties arise from higher-order multipoles that include quadrupoles and octupoles. Bragg spots that exclude all magnetic multipoles other than an octupole have been discovered, and they can be observed by both neutron diffraction and resonant x-ray diffraction. All magnetic multipoles allowed in diffraction by cerium ions
(
4
f
1
)
are presented in terms of coefficients in a well-documented and unusual magnetic ground state. Symmetry of the cerium site in the cubic structure constrains the coefficients. Our scattering amplitudes have an application in both neutron- and x-ray diffraction experiments on
Ce
2
Zr
2
O
7
, for example, and searches for the sought-after cerium octupole. Also presented for future use is a result for the total, energy-integrated magnetic neutron-scattering intensity by a powder sample.
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Dec 2022
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Open Access
Abstract: The technique of X-ray magnetic circular dichroism (XMCD) is presented from an experimental perspective. Absorption measurements in a net magnetic field can be performed using circularly polarized X-rays produced by bending magnets or insertion devices at the synchrotron and by employing detection methods such as X-ray transmission, total electron yield or fluorescence yield. XMCD is manifest in absorption edges of open-shell atoms, such as the K, L2,3 and M2,3 edges of transition metals, the L2,3, M4,5 and N4,5 edges of rare earths and the M4,5, N4,5 and O4,5 edges of actinides. The profoundly different characteristic line shapes provide a fingerprint for the spin and orbital character of the valence shell. The integrated intensities over the dichroic absorption edges can be related via sum rules to the expectation values of the spin and orbital magnetic moment in the ground state. The application of these sum rules has transformed XMCD into a powerful technique. This element-, site- and symmetry-specific technique enables a broad range of novel and exciting studies on the electronic and magnetic structure of modern materials.
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Dec 2022
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