Using a data sample corresponding to an integrated luminosity of 2.93 fb −1 collected at a centerof-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider, we search for a scalar partner of the X(3872), denoted as X(3700), via ψ(3770) → γηη and γπ + π − J/ψ processes. No significant signals are observed and the upper limits of the product branching fractions B(ψ(3770) → γX(3700))•B(X(3700) → ηη ) and B(ψ(3770) → γX(3700))•B(X(3700) → π + π − J/ψ) are determined at the 90% confidence level, for the narrow X(3700) with a mass ranging from 3710 to 3740 MeV/c 2 , which are from 0.8 to 1.8 (×10 −5 ) and 0.9 to 3.4 (×10 −5 ), respectively.

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The magnetic exchange bias effect is one of the representative interlayer magnetic coupling phenomena and is widely utilized in numerous technological applications. However, its mechanism is still elusive even in a simple magnetic bilayered system because of the complex interface magnetic orders. Van der Waals layered magnetic materials may provide an essential platform for deeply understanding the detailed mechanism of the exchange bias owing to its ideal interface structure. Here we first observed the positive exchange-biased anomalous Hall effect (AHE) with a hopping switching behavior in the FeGeTe Van der Waals nano-flakes. After systemically studying the cooling field dependence properties of the exchange bias effect, we propose that the coexistence of stable and frustrated surface magnetization of the antiferromagnetic phase will modify the total interface coupling energy density between the ferromagnetic (FM) and antiferromagnetic (AFM) phases. This model could provide a consistent description for such unusual exchange bias effect based on microspin simulation.

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Understanding and manipulating the dynamic properties of the magnetic vortices stabilized in patterned ferromagnetic structures are of great interest owing to the superior resonant features with the high thermal stability and their flexible tunability. So far, numerous methods for investigating the dynamic properties of the magnetic vortex have been proposed and demonstrated. However, those techniques have some regulations such as spatial resolution, experimental facility and sensitivity. Here, we develop a simple and sensitive method for investigating the vortex-core dynamics by using the electrically separated excitation and detection circuits. We demonstrate that the resonant oscillation of the magnetic vortex induced by the amplitude- modulated alternating-sign magnetic field is efficiently picked up by the lock-in detection with the modulated frequency. By extending this method, we also investigate the size dependence and the influence of the magneto-static interaction in the resonant property of the magnetic vortex.