Chirality-Induced Noncollinear Magnetization and Asymmetric Domain-Wall Propagation in Hydrogenated CoPd Thin Films.

Array-patterned CoPd-based heterostructures are created through e-beam lithography and plasma pretreatment that induces oxidation with depth gradient in the CoPd alloy films, breaking the central symmetry of the structure. Effects on the magnetic properties of the follow-up hydrogenation of the thin film are observed via magneto-optic Kerr effect microscopy. The system exhibits a strong vertical and lateral antiferromagnetic coupling in the perpendicular component between the areas with and without plasma pretreatment, and asymmetric domain-wall propagation in the plasma-pretreated areas during magnetization reversal. These phenomena exhibit evident magnetic chirality and can be interpreted with the Ruderman-Kittel-Kasuya-Yosida coupling and the Dzyaloshinskii-Moriya interaction (DMI). The sample processing demonstrated in this study allows easy incorporation of lithography techniques that can define areas with or without DMI to create intricate magnetic patterns on the sample, which provides an avenue toward more sophisticated control of canted spin textures in future spintronic devices.

Magnetic patterning through graphene protection against oxidation and interlayer diffusion.

Graphene (Gr) has been demonstrated to protect metallic thin films against oxidation. Based on this idea, we propose a new method to fabricate microstructured magnetic domains using patterned single-layer Gr. In the first experiment, single-layer Gr was transferred onto a CoPd alloy film pregrown on a SiO2/Si(001) substrate. Subsequently, the single-layer Gr was patterned through electron beam lithography followed by oxygen plasma etching to expose selective micron-sized areas of CoPd. The exposed areas of CoPd were more easily oxidized compared to the areas protected by Gr, which is found to result in significant magnetic contrast between the protected and surface-oxidized areas of CoPd. In the second experiment, a lithographically-patterned Gr layer was placed between the Fe and CoPd layers to block interlayer diffusion area-selectively during sample annealing. Magnetic contrast is observed to be established between the Pd/Fe/Gr/CoPd and Pd/Fe/CoPd areas, leading to a magnetic structure that matches the pattern of the lithographed Gr. These observations demonstrate that Gr patterning is a simple and powerful method for magnetic patterning, which can be applied in the fabrication of future data-storage and spintronic devices.

Multiphoton dynamic imaging of the effect of chronic hepatic diseases on hepatobiliary metabolism in vivo.

In this study, intravital multiphoton microscopy was used to quantitatively investigate hepatobiliary metabolism in chronic pathologies of the liver. Specifically, through the use of the probe molecule 6-carboxyfluorescein diacetate, the effects of liver fibrosis, fatty liver, and hepatocellular carcinoma on the metabolic capabilities of mouse liver were investigated. After the acquisition of time-lapse images, a first order kinetic model was used to calculate rate constant resolved images of various pathologies. It was found that the ability of the liver to metabolically process the probe molecules varies among different pathologies, with liver fibrosis and fatty liver disease negatively impacted the uptake, processing, and excretion of molecules. The approach demonstrated in this work allows the study of the response of hepatic functions to different pathologies in real time and is useful for studying processes such as pharmacokinetics through direct optical imaging.