2D materials exhibit superior properties in electronic and optoelectronic fields. The wide demand for high‐performance optoelectronic devices promotes the exploration of diversified 2D materials. Recently, 2D covalent organic frameworks (COFs) have emerged as next‐generation layered materials with predesigned π‐electronic skeletons and highly ordered topological structures, which are promising for tailoring their optoelectronic properties. However, COFs are usually produced as solid powders due to anisotropic growth, making them unreliable to integrate into devices. Here, by selecting tetraphenylethylene monomers with photoelectric activity, elaborately designed photosensitive 2D‐COFs with highly ordered donor‐acceptor topologies are in situ synthesized on graphene, ultimately forming COF‐graphene heterostructures. Ultrasensitive photodetectors are successfully fabricated with the COFETBC–TAPT‐graphene heterostructure and exhibited an excellent overall performance with a photoresponsivity of ≈3.2 × 107 A W−1 at 473 nm and a time response of ≈1.14 ms. Moreover, due to the high surface area and the polarity selectivity of COFs, the photosensing properties of the photodetectors can be reversibly regulated by specific target molecules. The research provides new strategies for building advanced functional devices with programmable material structures and diversified regulation methods, paving the way for a generation of high‐performance applications in optoelectronics and many other fields.

Ferromagnet/two-dimensional transition-metal dichalcogenide (FM/2D TMD) interfaces provide attractive opportunities to push magnetic information storage to the atomically thin limit. Existing work has focused on FMs contacted with mechanically exfoliated or chemically vapordeposition-grown TMDs, where clean interfaces cannot be guaranteed. Here, we report a reliable way to achieve contamination-free interfaces between ferromagnetic CoFeB and molecular-beam epitaxial MoSe 2 . We show a spin reorientation arising from the interface, leading to a perpendicular magnetic anisotropy (PMA), and reveal the CoFeB/2D MoSe 2 interface allowing for the PMA development in a broader CoFeB thickness-range than common systems such as CoFeB/MgO. Using X-ray magnetic circular dichroism analysis, we attribute generation of this PMA to interfacial d−d hybridization and deduce a general rule to enhance its magnitude. We also demonstrate favorable magnetic softness and considerable magnetic moment preserved at the interface and theoretically predict the interfacial band matching for spin filtering. Our work highlights the CoFeB/2D MoSe 2 interface as a promising platform for examination of TMD-based spintronic applications and might stimulate further development with other combinations of FM/2D TMD interfaces.

A series of Fe 3 O 4 particle chains with an average particle diameter of 150 nm and different lengths were synthesized by using the self-assembly method at reduced temperature in different synthesizing magnetic fields. The influence of synthesizing magnetic field on the properties of the magnetite particle chains was studied by structural analyses, magnetometry measurement, and ferromagnetic resonance. A uniaxial magnetic anisotropy in the saturation field (H s ), hysteresis loop, and ferromagnetic resonance were observed to increase with increasing synthesizing field. The saturation magnetization and g-factor were found to increase slightly with increasing synthesizing field. The demagnetizing fields and demagnetizing factors were determined from the experimental data of magnetometry measurement, ferromagnetic resonance, and also numerical calculation, which agreed reasonably well. It was found that the magnetization non-uniformity in the chains and the magnetostatic interaction among the chains have an important effect on the shape anisotropy of the chain assembly.

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Magnetic anisotropies of single crystal ultrathin Fe3O4 films on GaAs(100) have been studied by ferromagnetic resonance (FMR). The dependence of the FMR fields on the field orientation was measured both in plane and out of plane. The ultrathin films show predominantly an in-plane uniaxial magnetic anisotropy with the easy axis along the [0−11] direction of the GaAs substrate. The in-plane uniaxial anisotropy constant decreases with increasing thickness and changes from 7.1×104to2.1×104ergs∕cm3 when the thickness tFe varies from 4to8nm. An in-plane fourfold anisotropy due to cubic magnetocrystalline anisotropy coexists with the uniaxial magnetic anisotropy and increases with increasing film thickness. For tFe=8nm, the cubic anisotropy constant K1 reaches −8.4×104erg∕cm3, which is 76% of the value of bulk spinel Fe3O4. The out-of-plane measurements indicate a negative perpendicular anisotropy in these ultrathin Fe3O4 films.

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A 3.5 nm amorphous CoFeB film was sputtered on GaAs (001) wafer substrate without applying magnetic field during deposition, and a significant in-plane uniaxial magnetic anisotropy (UMA) field (Hu) of about 300 Oe could be achieved. To precisely determine the intrinsic Gilbert damping constant (α) of this film, both ferromagnetic resonance (FMR) and time-resolved magneto-optical Kerr effect (TRMOKE) techniques were utilized. With good fitting of the dynamic spectra of FMR and TRMOKE, α is calculated to be 0.010 and 0.013, respectively. Obviously, the latter is 30% larger than the former, which is due to the transient heating effect during the TRMOKE measurement. In comparison with ordinary amorphous CoFeB films with negligible magnetic anisotropies, α is enhanced significantly in the CoFeB/GaAs(001) film, which may be mainly resulted from the enhanced spin-orbit coupling induced by the CoFeB/GaAs interface. However, the significant in-plane UMA plays minor role in the enhancement of α.

The magnetic semiconductor with high critical temperature has long been the focus in material science and recently is also known as one of the fundamental questions in two-dimensional (2D) materials....