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36. Thermal contribution in the electrical switching experiments with heavy metal/antiferromagnet structures.

Author

Sheng, Peng, Zhao, Zhengyang, Benally, Onri Jay, Zhang, Delin, and Wang, Jian-Ping

Subjects
ANTIFERROMAGNETIC materials, HEAVY metals, EXPERIMENTAL design, HEATING
Abstract

We examine the thermal origin of the detected "saw-tooth" shaped Hall resistance (R xy ) signals in the spin–orbit torque switching experiment for antiferromagnetic MnN. Compared with the results of the heavy metal/antiferromagnet bilayers (MnN/Ta), the qualitatively same "saw-tooth" shaped signals also appear in the samples with the heavy metal layer alone (either Ta or Pt) without the MnN layer. In addition, the R xy signal changes oppositely in the devices with Ta and Pt, due to the opposite temperature coefficient of resistivity of the two materials. All those results are consistent with the "localized Joule heating" mechanism in devices with Hall crosses geometry. Moreover, by utilizing a structure with separated writing current paths and Hall cross area, the quadratic relationship between Δ R xy and the writing current's amplitude is observed, which provides quantitative evidence of the thermal contribution. These results reveal the dominant thermal artifact in the widely used Hall crosses geometry for Néel vector probing and also provide a strategy to semi-quantitatively evaluate the thermal effect, which can shed light on a more conclusive experiment design. [ABSTRACT FROM AUTHOR]

Published
2022
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37. Influence of surface acoustic wave (SAW) on nanoscale in-plane magnetic tunnel junctions.

Author

Zink, Brandon, Ma, Bin, Zhang, Delin, Bhattacharya, Dhritiman, Abeed, Md Ahsanul, Bandyopadhyay, Supriyo, Atulasimha, Jayasimha, and Wang, Jian-Ping

Subjects
ACOUSTIC surface waves, MAGNETIC tunnelling, TUNNEL magnetoresistance, MAGNETIC control, SAWS
Abstract

The use of voltage induced strain to switch magnetic tunnel junctions (MTJs) is a promising solution for reducing the switching energy in MRAM technologies. The MTJ is integrated with a piezoelectric layer to generate the strain. A very thin layer is needed to switch with small voltages and small energy dissipation. It is challenging to synthesize ultrathin piezoelectric layers that retain a high degree of piezoelectricity. An alternate approach is to use time-varying strain generated by a surface acoustic wave (SAW). This approach does not require a thin piezoelectric layer since the SAW is confined to the surface of the layer. In this study, we fabricated in-plane MTJs on piezoelectric LiNbO3 substrates and used IDTs to generate the SAW signal within the substrate. Our results showed that the SAW signal had a significant influence on the resistance and the tunneling magnetoresistance (TMR) ratio of the MTJs. The influence was much less significant in nanometer size MTJs than in micrometer sized ones. Most surprisingly, the SAW signal caused the tunneling magnetoresistance ratio (TMR) to drop below zero for the micrometer size MTJ, meaning that the antiparallel resistance RAP is temporarily less than the parallel resistance RP under SAW excitation. Our results provide insight into the dynamic behavior of MTJs under periodic strain and the dependence of this behavior on the device dimensions as they are scaled down to nanometer sizes. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Enhancement of voltage controlled magnetic anisotropy (VCMA) through electron depletion.

Author

Peterson, Thomas J., Hurben, Anthony, Jiang, Wei, Zhang, Delin, Zink, Brandon, Chen, Yu-Chia, Fan, Yihong, Low, Tony, and Wang, Jian-Ping

Subjects
MAGNETIC anisotropy, MAGNETIC control, VOLTAGE control, MAGNETIC tunnelling, ELECTRONS, HALL effect, SPIN-orbit interactions
Abstract

Recent advancement in the switching of perpendicular magnetic tunnel junctions with an electric field has been a milestone for realizing ultra-low energy memory and computing devices. To integrate with current spin-transfer torque-magnetic tunnel junction and spin–orbit torque-magnetic tunnel junction devices, the typical linear fJ/V m range voltage controlled magnetic anisotropy (VCMA) needs to be significantly enhanced with approaches that include new materials or stack engineering. A possible bidirectional and 1.1 pJ/V m VCMA effect has been predicted by using heavily electron-depleted Fe/MgO interfaces. To improve upon existing VCMA technology, we have proposed inserting high work function materials underneath the magnetic layer. This will deplete electrons from the magnetic layer biasing the gating window into the electron-depleted regime, where the pJ/V m and bidirectional VCMA effect was predicted. We have demonstrated tunable control of the Ta/Pd(x)/Ta underlayer's work function. By varying the Pd thickness (x) from 0 to 10 nm, we have observed a tunable change in the Ta layer's work function from 4.32 to 4.90 eV. To investigate the extent of the electron depletion as a function of the Pd thickness in the underlayer, we have performed DFT calculations on supercells of Ta/Pd(x)/Ta/CoFe/MgO, which demonstrate that electron depletion will not be fully screened at the CoFe/MgO interface. Gated pillar devices with Hall cross geometries were fabricated and tested to extract the anisotropy change as a function of applied gate voltage for samples with various Pd thicknesses. The electron-depleted Pd samples show three to six times VCMA improvement compared to the electron accumulated Ta control sample. [ABSTRACT FROM AUTHOR]

Published
2022
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42. A classification based on tumor budding and immune score for patients with hepatocellular carcinoma

Author

Li Wei, Zhang Delin, Yuan Kefei, Wu Hong, Huang Jiwei, and Zhang Yange

Subjects
hepatocellular carcinoma, tumor budding, immune score, prognosis, whole exome sequencing, Immunologic diseases. Allergy, RC581-607, Neoplasms. Tumors. Oncology. Including cancer and carcinogens, RC254-282
Abstract

Background: The role of immune profiling and tumor budding in hepatocellular carcinoma (HCC) remains largely unknown. This study evaluated the association between tumor budding and lymphocytic infiltration in HCC. Meanwhile, HCC patients were stratified based on tumor budding grade and immune score. Patients and methods: A total of 423 HCC patients were divided into training (n = 212) and validation (n = 211) cohort. Tumor slides from resected HCC samples were used for tumor budding assessment. A prognosis-relevant immune score was developed based on five types of immune cells out of eleven immune markers. A classification based on tumor budding grade and immune type was established (IS-TB type). To explore the association of IS-TB type and molecular alterations of HCC, 100 HCC samples and adjacent non-tumor tissues from 100 patients were investigated by whole-exome sequencing. Results: Tumor budding was an independent adverse prognostic factor for OS and DFS in both of the training and validation cohorts (all P values

Published
2020
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45. WTAP–VIRMA counteracts dsDNA binding of the m6A writer METTL3–METTL14 complex and maintains N6-adenosine methylation activity.

Author

Yan, Xuhui, Liu, Feiqing, Yan, Junjun, Hou, Mengjun, Sun, Min, Zhang, Delin, Gong, Zhou, Dong, Xu, Tang, Chun, and Yin, Ping

Subjects
SMALL nuclear RNA, METHYLATION, NUCLEIC acids, GENE enhancers
Abstract

WTAP-VIRMA counteracts dsDNA binding of the m6A writer METTL3-METTL14 complex and maintains N6-adenosine methylation activity Therefore, the RGG of METTL14 helps METTL3-METTL14 bind to nucleic acids and supports the interaction between METTL3-METTL14 and WTAP-VIRMA. Upon addition of the unlabeled WTAP-VIRMA SP 381-1486 sp , ssRNA SB GGACU sb , ssRNA SB UUUUU sb , or dsDNA SB 50 sb to the SP 15 sp N-labeled RGG, a similar set of peaks were found to be perturbed, meaning that WTAP-VIRMA SP 381-1486 sp , dsDNA SB 50 sb , ssRNA SB GGACU sb , and ssRNA SB UUUUU sb interact with the RGG of METTL3-METTL14 via a similar interface, which may lead to their competitive binding to METTL3-METTL14. In METTL3-METTL14, two types of nucleic acid-binding domains were identified[2], including the zinc finger domain (ZFD) in METTL3 and the RGG motif (RGG) in METTL14. [Extracted from the article]

Published
2023
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46. Observation and enhancement of room temperature bilinear magnetoelectric resistance in sputtered topological semimetal Pt3Sn

Author

Fan, Yihong, Cresswell, Zach, Yang, Yifei, Jiang, Wei, Lv, Yang, Peterson, Thomas, Zhang, Delin, Liu, Jinming, Low, Tony, and Wang, Jian-ping

Subjects
Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Applied Physics (physics.app-ph), Physics - Applied Physics
Abstract

Topological semimetal materials have become a research hotspot due to their intrinsic strong spin-orbit coupling which leads to large charge-to-spin conversion efficiency and novel transport behaviors. In this work, we have observed a bilinear magnetoelectric resistance (BMER) of up to 0.1 nm2A-1Oe-1 in a singlelayer of sputtered semimetal Pt3Sn at room temperature. Different from previous observations, the value of BMER in sputtered Pt3Sn does not change out-of-plane due to the polycrystalline nature of Pt3Sn. The observation of BMER provides strong evidence of the existence of spin-momentum locking in the sputtered polycrystalline Pt3Sn. By adding an adjacent CoFeB magnetic layer, the BMER value of this bilayer system is doubled compared to the single Pt3Sn layer. This work broadens the material system in BMER study, which paves the way for the characterization of topological states and applications for spin memory and logic devices.

Published
2023

47. Robust negative longitudinal magnetoresistance and spin-orbit torque in sputtered Pt3Sn topological semimetal

Author

Zhang, Delin, Jiang, Wei, Yun, Hwanhui, Benally, Onri Jay, Peterson, Thomas, Cresswell, Zach, Fan, Yihong, Lv, Yang, Yu, Guichuan, Barriocanal, Javier Garcia, Swatek, Przemyslaw, Mkhoyan, K. Andre, Low, Tony, and Wang, Jian-Ping

Subjects
Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Contrary to topological insulators, topological semimetals possess a nontrivial chiral anomaly that leads to negative magnetoresistance and are hosts to both conductive bulk states and topological surface states with intriguing transport properties for spintronics. Here, we fabricate highly-ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering technology. Systematic angular dependence (both in-plane and out-of-plane) study of magnetoresistance presents surprisingly robust quadratic and linear negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x, respectively. We attribute the anomalous negative longitudinal magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or the formation of tunable Weyl semimetal phases through symmetry breaking processes, such as magnetic-atom doping, as confirmed by first-principles calculations. Furthermore, Pt3Sn and Pt3SnxFe1-x show the promising performance for facilitating the development of advanced spin-orbit torque devices. These results extend our understanding of chiral anomaly of topological semimetals and can pave the way for exploring novel topological materials for spintronic devices., 13 pages, 4 figures

Published
2023

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