2 Charged particles exhibit the Hall effect in the presence of magnetic fields. Analogously, ferromagnetic skyrmions with non-zero topological charges and finite fictitious magnetic fields exhibit the skyrmion Hall effect, which is detrimental for applications. The skyrmion Hall effect has been theoretically predicted to vanish for antiferromagnetic skyrmions because the fictitious magnetic field, proportional to net spin density, is zero. We experimentally confirm this prediction by observing currentdriven transverse elongation of pinned ferrimagnetic bubbles. Remarkably, the skyrmion Hall effect, estimated with the angle between the current and bubble elongation directions, vanishes at the angular momentum compensation temperature where the net spin density vanishes. This study establishes a direct connection between the fictitious magnetic field and spin density, offering a pathway towards the realization of skyrmionic devices.

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Enzyme-containing polymer−single walled carbon nanotube (SWNT) composites have been explored as unique biocatalytic materials. The biocatalytic composites were prepared by suspending SWNT and r-chymotrypsin (CT) directly into a poly(methyl methacrylate) solution in toluene. The activity of the resulting CT−polymer−nanotube films was observed to be higher than both polymer−CT and polymer−graphite−CT films. The effect of SWNT loading on biocatalytic activity was also studied, and the optimal SWNT loading was used to compare the biocatalytic performance of different polymer−SWNT systems. In all polymers tested, SWNT-containing composites show higher enzyme activity than the non-SWNT preparations. This was most likely due to a reduction in the leaching of enzyme from the film in the former, perhaps caused by the adsorption of enzyme molecules onto highly structured and high energy SWNTs within the polymer matrix. Investigation of different polymer composites indicates that SWNTs may be used to improve the performance of a wide range of biocatalytic composites for applications ranging from antifouling surface coatings to sensor elements.

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