I10-Beamline for Advanced Dichroism
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Zihan
Li
,
Shanshan
Liu
,
Jiabao
Sun
,
Jiayi
Zhu
,
Yanhui
Chen
,
Yunkun
Yang
,
Linfeng
Ai
,
Enze
Zhang
,
Ce
Huang
,
Pengliang
Leng
,
Minhao
Zhao
,
Xiaoyi
Xie
,
Yuda
Zhang
,
Nesta Benno
Joseph
,
Rajdeep
Banerjee
,
Awadhesh
Narayan
,
Jin
Zou
,
Wenqing
Liu
,
Xiaodong
Xu
,
Faxian
Xiu
Diamond Proposal Number(s):
[22532]
Abstract: Two-dimensional (2D) magnets offer valuable electrical and mechanical properties, and could be used to create 2D nanoelectromechanical systems. However, the low Curie temperature of most 2D magnets limits practical applications. Here we report van der Waals ferromagnetic low-pass filters based on wafer-scale iron germanium telluride (Fe5+xGeTe2) thin films grown by molecular-beam epitaxy. We show that the Curie temperature of the Fe5+xGeTe2 system can be continuously modulated from 260 to 380 K via in situ iron doping. Few-layer Fe5+xGeTe2 is used to fabricate planar spiral inductors, with the 2D magnetic core providing inductance enhancement of 74% at room temperature compared with an inductor without the core. Low-pass Butterworth filters are then created from inductance–capacitance circuits built with these inductors. The filters offer a broad dynamic range of around 40 dB, and the –3 dB cut-off frequency can be tuned from 18 to 30 Hz by using different inductors in the inductance–capacitance circuit.
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Mar 2023
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I10-Beamline for Advanced Dichroism
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Xiaoqian
Zhang
,
Wenqing
Liu
,
Wei
Niu
,
Qiangsheng
Lu
,
Wei
Wang
,
Ali
Sarikhani
,
Xiaohua
Wu
,
Chunhui
Zhu
,
Jiabao
Sun
,
Mitchel
Vaninger
,
Paul. F.
Miceli
,
Jianqi
Li
,
David J.
Singh
,
Yew San
Hor
,
Yue
Zhao
,
Chang
Liu
,
Liang
He
,
Rong
Zhang
,
Guang
Bian
,
Dapeng
Yu
,
Yongbing
Xu
Diamond Proposal Number(s):
[22532]
Abstract: One of the most promising avenues in 2D materials research is the synthesis of antiferromagnets employing 2D van der Waals (vdW) magnets. However, it has proven challenging, due in part to the complicated fabrication process and undesired adsorbates as well as the significantly deteriorated ferromagnetism at atomic layers. Here, the engineering of the antiferromagnetic (AFM) interlayer exchange coupling between atomically thin yet ferromagnetic CrTe2 layers in an ultra-high vacuum-free 2D magnetic crystal, Cr5Te8 is reported. By self-introducing interstitial Cr atoms in the vdW gaps, the emergent AFM ordering and the resultant giant magnetoresistance effect are induced. A large negative magnetoresistance (10%) with a plateau-like feature is revealed, which is consistent with the AFM interlayer coupling between the adjacent CrTe2 main layers in a temperature window of 30 K below the Néel temperature. Notably, the AFM state has a relatively weak interlayer exchange coupling, allowing a switching between the interlayer AFM and ferromagnetic states at moderate magnetic fields. This work represents a new route to engineering low-power devices that underpin the emerging spintronic technologies, and an ideal laboratory to study 2D magnetism.
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May 2022
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I10-Beamline for Advanced Dichroism
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Diamond Proposal Number(s):
[16538]
Open Access
Abstract: As an emerging class of two-dimensional (2D) materials, van der Waals (vdW) magnets have attracted a lot of research attention since they can give access to fundamental physics and potential spintronic device applications. Among these 2D vdW magnets, CrSiTe3, as an intrinsic ferromagnetic semiconductor, exhibits great potentials in low-dimensional spintronics. Of particular interest in this 2D vdW magnet is the electronic and magnetic properties at the atomic-scale, which has yet been fully explored so far. Here, combing angle-resolved photoemission spectroscopy, bulk magnetic measurements, and synchrotron-based x-ray techniques, an unambiguous picture of the electronic and magnetic states of CrSiTe3 is presented. Hybridization of Cr-3d and Te-5p orbitals and the semiconducting behavior are confirmed by the band structure detection. Intrinsic ferromagnetism with a magnetic anisotropy constant of 1.56 × 105 erg/cm3 is attributed to the superexchange interaction of the Cr3+ ions. In addition, temperature-dependent spin and orbital moments are determined, and a fitted critical exponent of 0.169 implies that CrSiTe3 is in good agreement with the 2D Ising model. More remarkably, unquenched orbital moments are experimentally evidenced, bringing CrSiTe3 with orbital-dependent intriguing effects and great potentials toward the spintronic devices.
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Oct 2021
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I10-Beamline for Advanced Dichroism
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Xiaoqian
Zhang
,
Qiangsheng
Lu
,
Wenqing
Liu
,
Wei
Niu
,
Jiabao
Sun
,
Jacob
Cook
,
Mitchel
Vaninger
,
Paul F.
Miceli
,
David J.
Singh
,
Shang-Wei
Lian
,
Tay-Rong
Chang
,
Xiaoqing
He
,
Jun
Du
,
Liang
He
,
Rong
Zhang
,
Guang
Bian
,
Yongbing
Xu
Diamond Proposal Number(s):
[22532]
Open Access
Abstract: While the discovery of two-dimensional (2D) magnets opens the door for fundamental physics and next-generation spintronics, it is technically challenging to achieve the room-temperature ferromagnetic (FM) order in a way compatible with potential device applications. Here, we report the growth and properties of single- and few-layer CrTe2, a van der Waals (vdW) material, on bilayer graphene by molecular beam epitaxy (MBE). Intrinsic ferromagnetism with a Curie temperature (TC) up to 300 K, an atomic magnetic moment of ~0.21 𝜇B
μ
B
/Cr and perpendicular magnetic anisotropy (PMA) constant (Ku) of 4.89 × 105 erg/cm3 at room temperature in these few-monolayer films have been unambiguously evidenced by superconducting quantum interference device and X-ray magnetic circular dichroism. This intrinsic ferromagnetism has also been identified by the splitting of majority and minority band dispersions with ~0.2 eV at Г point using angle-resolved photoemission spectroscopy. The FM order is preserved with the film thickness down to a monolayer (TC ~ 200 K), benefiting from the strong PMA and weak interlayer coupling. The successful MBE growth of 2D FM CrTe2 films with room-temperature ferromagnetism opens a new avenue for developing large-scale 2D magnet-based spintronics devices.
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May 2021
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I10-Beamline for Advanced Dichroism
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Wei
Niu
,
Yue‐wen
Fang
,
Xiaoqian
Zhang
,
Yakui
Weng
,
Yongda
Chen
,
Hui
Zhang
,
Yulin
Gan
,
Xiao
Yuan
,
Shengjie
Zhang
,
Jiabao
Sun
,
Yile
Wang
,
Lujun
Wei
,
Yongbing
Xu
,
Xuefeng
Wang
,
Wenqing
Liu
,
Yong
Pu
Diamond Proposal Number(s):
[20748]
Abstract: Transition‐metal oxide (TMO) heterostructures provide fertile grounds for creating and manipulating intriguing properties and functionalities. At the interface of TMO heterostructures, electronic reconstructions generally occur via charge transfer and lead to an extraordinary spectrum of emergent phenomena but unattainable in their bulk constituents. However, the basic mechanism of charge transfer at the interface is not fully determined or even understood in heterostructures, which may hide the underlying mechanisms and intriguing physics. Herein, an intrinsic charge transfer and resultant exotic ferromagnetism are unambiguously observed in the heterostructures between the nonmagnetic LaCoO3 (LCO) and SrTiO3 (STO). Combining element‐specific X‐ray absorption spectroscopy and atomic multiplet fitting, direct evidence of charge transfer‐induced multivalence of cobalt ions, interactions of which would contribute to the novel magnetism beyond the intuition, in concert with first‐principles density‐functional‐theory calculations, is demonstrated. Beyond LCO/STO system, a more broadly applicable principle for the heterostructures between 3d TMO and STO where charge transfer and resultant multivalence or conducting interfaces are coexistent is establish. This study represents an advance that the electronic reconstruction and the multiple electron configurations of 3d transition metal ions will constitute a powerful tool for the designs of functional materials and creations of unconventional physical properties.
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Nov 2020
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I06-Nanoscience
I10-Beamline for Advanced Dichroism
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Zhongchong
Lin
,
Liang
Zha
,
Fanggui
Wang
,
Zhou
Liu
,
Rui
Wu
,
Jie
Yang
,
Mingzhu
Xue
,
Wenyun
Yang
,
Guang
Tian
,
Xiaobai
Ma
,
Liang
Qiao
,
Alexandra
Franz
,
Qi
An
,
Wenqing
Liu
,
Changsheng
Wang
,
Jinbo
Yang
Diamond Proposal Number(s):
[16538]
Abstract: The effect of Ce substitution on the structural and magnetic properties of (Nd1-δCeδ)2Fe14B (0 < δ < 1) series was systematically studied using neutron diffraction, 57Fe Mössbauer spectroscopy and X-ray magnetic circular dichroism (XMCD). An anomaly in the lattice parameters was observed in a sample with composition in the range of 0.2 < δ < 0.4, where a phase separation happens and the 2:14:1 isostructural dual-main-phases (IDMPs) appear. Outside this composition range, Ce shows a preferential occupation at the 4g site than the 4f site and a preferable Ce3+ valence state. The average magnetic moments of Nd/Ce and Fe atoms decrease with the increasing of δ. The magnitude of the Fe moments at non-equivalent sites is related to several factors, such as the Fe coordination number, the Wigner-Seitz cell volume, and the Boron atom effect. These results reveal the microscopic mechanisms for the structural and magnetic properties of Ce-substitution Nd2Fe14B, providing perspective on developing the next-generation low-cost and high-performance permanent magnetic materials.
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Nov 2020
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I10-Beamline for Advanced Dichroism
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Zhendong
Chen
,
Wenqing
Liu
,
Peng
Chen
,
Xuezhong
Ruan
,
Jiabao
Sun
,
Ruobai
Liu
,
Cunxu
Gao
,
Jun
Du
,
Bo
Liu
,
Hao
Meng
,
Rong
Zhang
,
Yongbing
Xu
Diamond Proposal Number(s):
[22532]
Abstract: Compensated ferrimagnetic Heusler compounds with high spin polarization and a low net magnetic moment are strategically important materials for spin-logic and further energy-efficient spintronic applications. However, the element-resolved magnetic ordering of these compensated ferrimagnets remains an open issue. Here, we report a direct observation of the spin and orbital moments of the B2 phase Mn2CoAl thin film using the synchrotron-based x-ray magnetic circular dichroism technique. An ferrimagnetic ordering between Mn and Co elements and a compensated-ferrimagnet-like small net magnetic moment of only 0.34 μB/f.u. were observed unambiguously in B2 Mn2CoAl. Antiparallel coupling between Mn and Co is attributed to the mixture of the Mn(B) and Al occupation in the B2 phase Mn2CoAl lattice. This work demonstrates great potential of the compensated ferrimagnetic half-metallic inverse Heusler compounds Mn2CoAl for spintronic applications.
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Jul 2020
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Zhonghui
Nie
,
Ion Cristian Edmond
Turcu
,
Yao
Li
,
Xiaoqian
Zhang
,
Liang
He
,
Jian
Tu
,
Zhiqiang
Ni
,
Huangfeng
Xu
,
Yequan
Chen
,
Xuezhong
Ruan
,
Fabio
Frassetto
,
Paolo
Miotti
,
Nicola
Fabris
,
Luca
Poletto
,
Jing
Wu
,
Qiangsheng
Lu
,
Chang
Liu
,
Thorsten
Kampen
,
Ya
Zhai
,
Wenqing
Liu
,
Cephise
Cacho
,
Xuefeng
Wang
,
Fengqiu
Wang
,
Yi
Shi
,
Rong
Zhang
,
Yongbing
Xu
Open Access
Abstract: A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the “Ultrafast Spintronic Materials Facility”, dedicated to engineering ultrafast materials. This facility provides a fast and in-situ analysis and development of new materials. The EUV source based on high harmonic generation process emits 2.3 × 1011 photons/second (2.3 × 108 photons/pulse) at H23 (35.7 eV) and its photon energy ranges from 10 eV to 75 eV, which enables surface sensitive studies of the electronic structure dynamics. The EUV monochromator provides the narrow bandwidth of the EUV beamline while preserving its pulse duration in an energy range of 10–100 eV. Ultrafast surface photovoltaic effect with ~650 fs rise-time was observed in p-GaAs (100) from time-resolved ARPES spectra. The data acquisition time could be reduced by over two orders of magnitude by scaling the laser driver from 1 KHz, 4W to MHz, KW average power.
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Jan 2019
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