Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.

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Diabetes mellitus is a chronic disease affecting patients' daily life and increasing patients' risk of other complication. Dipeptidyl peptidase-4 (DPP-4) is a serine aminopeptidase, which is one of the validated targets for Type 2 diabetes therapy due to its regulatory effect of incretin hormone. Seven DPP-4 inhibitors are commercially available nowadays on the market as Type 2 diabetes drugs. They are all chemically synthesized compounds with good therapeutic effects, but long-term safety remains unknown. On the other hand, nature provides a rich source for search of desired safe and effective medications; and actually more than half of the drugs on market are natural product related. Therefore, a systematic search for new DPP-4 inhibitors from nature sources seems to be of great utility for developing novel antidiabetic drugs. This review summarized recent progress of DPP-4 inhibitors from natural products, revealed that both pure natural products and the crude extracts of herbs or the hydrolyzates of proteins are active as DPP-4 inhibitors. Therefore, both could be served as useful clues for developing next generation of antidiabetes medicines via inhibiting DPP-4 activity.

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Optical control of spin is of central importance in the research of ultrafast spintronic devices utilizing spin dynamics at short time scales. Recently developed optical approaches such as ultrafast demagnetization, spin-transfer and spin-orbit torques open new pathways to manipulate spin through its interaction with photon, orbit, charge or phonon. However, these processes are limited by either the long thermal recovery time or the low-temperature requirement. Here we experimentally demonstrate ultrafast coherent spin precession via optical charge-transfer processes in the exchange-coupled Fe/CoO system at room temperature. The efficiency of spin precession excitation is significantly higher and the recovery time of the exchange-coupling torque is much shorter than for the demagnetization procedure, which is desirable for fast switching. The exchange coupling is a key issue in spin valves and tunnelling junctions, and hence our findings will help promote the development of exchange-coupled device concepts for ultrafast coherent spin manipulation.