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Creators/Authors contains: "Wang, Xinjun"

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  1. Abstract

    Spatial transcriptomics technologies have shed light on the complexities of tissue structures by accurately mapping spatial microenvironments. Nonetheless, a myriad of methods, especially those utilized in platforms like Visium, often relinquish spatial details owing to intrinsic resolution limitations. In response, we introduce TransformerST, an innovative, unsupervised model anchored in the Transformer architecture, which operates independently of references, thereby ensuring cost-efficiency by circumventing the need for single-cell RNA sequencing. TransformerST not only elevates Visium data from a multicellular level to a single-cell granularity but also showcases adaptability across diverse spatial transcriptomics platforms. By employing a vision transformer-based encoder, it discerns latent image-gene expression co-representations and is further enhanced by spatial correlations, derived from an adaptive graph Transformer module. The sophisticated cross-scale graph network, utilized in super-resolution, significantly boosts the model’s accuracy, unveiling complex structure–functional relationships within histology images. Empirical evaluations validate its adeptness in revealing tissue subtleties at the single-cell scale. Crucially, TransformerST adeptly navigates through image-gene co-representation, maximizing the synergistic utility of gene expression and histology images, thereby emerging as a pioneering tool in spatial transcriptomics. It not only enhances resolution to a single-cell level but also introduces a novel approach that optimally utilizes histology images alongside gene expression, providing a refined lens for investigating spatial transcriptomics.

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    Controlling magnetization dynamics is imperative for developing ultrafast spintronics and tunable microwave devices. However, the previous research has demonstrated limited electric-field modulation of the effective magnetic damping, a parameter that governs the magnetization dynamics. Here, we propose an approach to manipulate the damping by using the large damping enhancement induced by the two-magnon scattering and a nonlocal spin relaxation process in which spin currents are resonantly transported from antiferromagnetic domains to ferromagnetic matrix in a mixed-phased metallic alloy FeRh. This damping enhancement in FeRh is sensitive to its fraction of antiferromagnetic and ferromagnetic phases, which can be dynamically tuned by electric fields through a strain-mediated magnetoelectric coupling. In a heterostructure of FeRh and piezoelectric PMN-PT, we demonstrated a more than 120% modulation of the effective damping by electric fields during the antiferromagnetic-to-ferromagnetic phase transition. Our results demonstrate an efficient approach to controlling the magnetization dynamics, thus enabling low-power tunable electronics. 
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  5. Abstract

    Over the past decades, optical manipulation of magnetization by ultrafast laser pulses has attracted extensive interest. It not only shows intriguing fundamental science arising from the interactions between spins, electrons, phonons, and photons, but also manifests the potential to process and store data at a speed that is three orders of magnitude faster than the current technologies. In this paper, all‐optical helicity‐dependent switching (AO‐HDS) in hybrid metal–ferromagnet thin films, which consist of Co/Pt multilayers with perpendicular magnetic anisotropy and an Au film capping layer on the top, is experimentally demonstrated. The switching behaviors of the hybrid Co/Pt–Au material, with various laser repetition rates, scanning speeds, and fluencies, are systematically studied. In comparison with bare Co/Pt multilayers, the hybrid metal–ferromagnet thin films show pronounced AO‐HDS when the number of laser pulses per μm along the scanning direction gradually increases. In addition, the AO‐HDS effect is very robust against laser fluences. A possible mechanism is further proposed based on numerical simulations of the optomagnetic coupling model. These findings promise a new material system that exhibits stable AO‐HDS phenomena, and hence can transform future magnetic storage devices, especially with the addition of plasmonic nanostructures made of noble metals.

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  6. Abstract

    Magnetization dynamics induced by spin–orbit torques in a heavy‐metal/ferromagnet can potentially be used to design low‐power spintronics and logic devices. Recent computations have suggested that a strain‐mediated spin–orbit torque (SOT) switching in magnetoelectric (ME) heterostructures is fast, energy‐efficient, and permits a deterministic 180° magnetization switching. However, its experimental realization has remained elusive. Here, the coexistence of the strain‐mediated ME coupling and the SOT in a CoFeB/Pt/ferroelectric hybrid structure is shown experimentally. The voltage‐induced strain only slightly modifies the efficiency of SOT generation, but it gives rise to an effective magnetic anisotropy and rotates the magnetic easy axis which eliminates the incubation delay in current‐induced magnetization switching. The phase field simulations show that the electric‐field‐induced effective magnetic anisotropy field can reduce the switching time approximately by a factor of three for SOT in‐plane magnetization switching. It is anticipated that such strain‐mediated ME‐SOT hybrid structures may enable field‐free, ultrafast magnetization switching.

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