Two-dimensional van der Waals (2D vdW) magnets have attracted great attention recently and possess the unprecedented advantages of incorporating high-quality vdW heterostructures and homostructures into spintronic devices, and exploring various physical phenomena or technologies. Among them, Fe₅GeTe₂ (F5GT) has ferromagnetic order close to room temperature, however the magnetic properties near its intrinsic transitions and F5GT-based 2D devices remain mostly unexplored. Here, we systematically demonstrate the peculiar magnetic properties of Fe₅GeTe₂ nanoflakes near its intrinsic transition temperature (T_p) which is far lower than its Curie temperature (T_C) of ~ 265 K, and firstly discover anomalous magnetoresistance effect in F5GT homo-junctions by magneto-transport measurements. The strongest anomalous Hall effect occurs around T_p which is located in a temperature range from 130 to 160 K for the F5GT nanoflakes with different thicknesses. Furthermore, negative magnetoresistance (N-MR) and butterfly-shaped magnetoresistance (B-MR) are observed in F5GT homo-junction devices, and they appeared only in an intermediate temperature range from 110 to 160 K, noticeably showing the maxima near the T_p rather than the lowest temperature. Our experimental results clearly reveal the significant influence of intrinsic transitions on magnetic properties of F5GT and magnetoresistance effect in F5GT homo-junction devices, which imply a new strategy to achieve high-performance 2D spintronic devices by tuning intrinsic magnetic or structural transitions in 2D vdW magnets.

Tunable behavior in electrocatalysis by external multifields, such as magnetic field, thermal field, and electric field, is the most promising strategy to expand the theory, design, and synthesis of state-of-the-art catalysts and the cell in the near future. Here, a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions (MOR) in magnetic nanoparticles is reported. For Co₄₂Pt₅₈ truncated octahedral nanoparticles (TONPs), the catalytic performance in MOR is greatly increased to the maximum of 14.1% by applying a magnetic field up to 3000 Oe, and it shows a monotonical increase with increasing working temperature. The magnetic enhanced effect is closely related to the Co content of Co_xPt_100-x TONPs. Furthermore, the enhancement effect under a magnetic field is more obvious for Co₄₂Pt₅₈ TONPs annealed at 650 ℃. First-principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier, where OH_ad intermediates on Co sites play a more important role. The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells, which will accelerate their potential applications.