Mn12 and the dawn of single-molecule magnets
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Magnetic and mechanical hardening of nano-lamellar magnets using thermo-magnetic fields
High-performance magnetic materials based on rare-earth intermetallic compounds are critical for energy conversion technologies. However, the high cost and supply risks of rare-earth elements necessitate the development of affordable alternatives. Another challenge lies in the inherent brittleness of current magnets, which limits their applications for high dynamic mechanical loading conditions during service and complex shape design during manufacturing towards high efficiency and sustainability. Here, we propose a strategy to simultaneously enhance the magnetic and mechanical performance of a rare-earth-free multicomponent magnet. We achieve this by introducing nano-lamellar structures with high shape anisotropy into a cobalt–iron–nickel–aluminum material system through eutectoid decomposition under externally applied thermo-magnetic fields. Compared to the conventional thermally activated processing, the thermo-magnetic field accelerates phase decomposition kinetics, producing finer lamellae spacings and smaller eutectoid colonies. The well-tailored size, density, interface, and chemistry of the nano-lamellae enhance their pinning effect against the motion of both magnetic domain walls and dislocations, resulting in concurrent gains in coercivity and mechanical strength. Our work demonstrates a rational pathway to designing multifunctional rare-earth-free magnets for energy conversion devices such as high-speed motors and generators operating under harsh service conditions.
Current-induced motion of nanoscale magnetic torons over the wide range of the Hall angle
Current-driven dynamics of topological spin textures plays a pivotal role in potential applications for electronic devices. While two-dimensional magnetic skyrmions have garnered significant interest, their practical use is hindered by the skyrmion Hall effect—a transverse motion to the current direction that occurs as a counteraction to the topological Hall effect of electrons arising from the Berry phase effect. Here, we explore current-driven dynamics of three-dimensional topological spin textures, magnetic torons, composed of layered skyrmions with two singularities called Bloch points at their ends. Through extensive numerical simulations, we show that torons exhibit a unique Hall motion ranging from the zero Hall effect, a purely longitudinal motion, to the perfect Hall effect, a purely transverse motion accompanied by no longitudinal motion. Such flexible and controllable behaviors stem from anisotropic potential barriers on the discrete lattice for nanoscale torons. Our results provide a method to probe the topology of three-dimensional magnetic textures and contribute to advanced topological spintronics beyond the realm of skyrmions.
Achievement of a vacuum-levitated metal mechanical oscillator with ultra-low damping rate at room temperature
A vacuum-levitated metal mechanical oscillator with an ultra-low damping rate is an ideal tool for detecting mass-related short-range forces; however, its realization at room temperature has not yet been achieved, limiting its practical applications. In this study, we developed such an oscillator using a diamagnetically levitated bismuth sphere. We derived an accurate general formula for the sphere’s eddy current damping rate and, based on this, constructed the oscillator from microparticles, successfully reducing its damping rate experimentally to (144 ± 6) μHz—nearly three orders of magnitude lower than that of the untreated sphere. This improvement allows the sub-millimeter-sized levitated metal mechanical oscillator to theoretically achieve a force sensitivity of ((5.17pm 0.12),,{mbox{fN}}/sqrt{{mbox{Hz}},}) and an acceleration sensitivity of ((0.30pm 0.01),,{mbox{ng}}/sqrt{{mbox{Hz}},}) at room temperature. Calculations indicate that using this sphere as a test mass can detect gravitational forces from sub-milligram sources, highlighting its potential for short-range force sensing and the exploration of quantum gravity.
Diffraction minima resolve point scatterers at few hundredths of the wavelength
Resolving two or more constantly scattering identical point sources using freely propagating waves is limited by diffraction. Here we show that, by illuminating with a diffraction minimum, a given number of point scatterers can be resolved at distances of small fractions of the wavelength. Specifically, we identify an 8 nm distance, which corresponds to 1/80 of the employed 640 nm wavelength, between two constantly emitting fluorescent molecules in the focal plane of an optical microscope. We also measure 22 nm side length for a quadratic array of four molecules. Moreover, we show that the measurement precision improves with decreasing distance and with increased scatterer density. This work opens up the prospect of resolving individual scatterers in clusters that are far smaller than the wavelength.
Single-molecule live-cell RNA imaging with CRISPR–Csm
Understanding the diverse dynamic behaviors of individual RNA molecules in single cells requires visualizing them at high resolution in real time. However, single-molecule live-cell imaging of unmodified endogenous RNA has not yet been achieved in a generalizable manner. Here, we present single-molecule live-cell fluorescence in situ hybridization (smLiveFISH), a robust approach that combines the programmable RNA-guided, RNA-targeting CRISPR–Csm complex with multiplexed guide RNAs for direct and efficient visualization of single RNA molecules in a range of cell types, including primary cells. Using smLiveFISH, we track individual native NOTCH2 and MAP1B transcripts in living cells and identify two distinct localization mechanisms including the cotranslational translocation of NOTCH2 mRNA at the endoplasmic reticulum and directional transport of MAP1B mRNA toward the cell periphery. This method has the potential to unlock principles governing the spatiotemporal organization of native transcripts in health and disease.
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