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Abstract Current induced spin-orbit torque (SOT) holds great promise for next generation magnetic-memory technology. Field-free SOT switching of perpendicular magnetization requires the breaking of in-plane symmetry, which can be artificially introduced by external magnetic field, exchange coupling or device asymmetry. Recently it has been shown that the exploitation of inherent crystal symmetry offers a simple and potentially efficient route towards field-free switching. However, applying this approach to the benchmark SOT materials such as ferromagnets and heavy metals is challenging. Here, we present a strategy to break the in-plane symmetry of Pt/Co heterostructures by designing the orientation of Burgers vectors of dislocations. We show that the lattice of Pt/Co is tilted by about 1.2° when the Burgers vector has an out-of-plane component. Consequently, a tilted magnetic easy axis is induced and can be tuned from nearly in-plane to out-of-plane, enabling the field-free SOT switching of perpendicular magnetization components at room temperature with a relatively low current density (~10¹¹A/m²) and excellent stability (> 10⁴cycles). This strategy is expected to be applicable to engineer a wide range of symmetry-related functionalities for future electronic and magnetic devices. 

ABSTRACT Wind-driven upwelling followed by relaxation results in cycles of cold nutrient-rich water fueling intense phytoplankton blooms followed by nutrient depletion, bloom decline, and sinking of cells. Surviving cells at depth can then be vertically transported back to the surface with upwelled waters to seed another bloom. As a result of these cycles, phytoplankton communities in upwelling regions are transported through a wide range of light and nutrient conditions. Diatoms appear to be well suited for these cycles, but their responses to them remain understudied. To investigate the bases for diatoms’ ecological success in upwelling environments, we employed laboratory simulations of a complete upwelling cycle with a common diatom, Chaetoceros decipiens , and coccolithophore, Emiliania huxleyi . We show that while both organisms exhibited physiological and transcriptomic plasticity, the diatom displayed a distinct response enabling it to rapidly shift-up growth rates and nitrate assimilation when returned to light and available nutrients following dark nutrient-deplete conditions. As observed in natural diatom communities, C. decipiens highly expresses before upwelling, or frontloads, key transcriptional and nitrate assimilation genes, coordinating its rapid response to upwelling conditions. Low-iron simulations showed that C. decipiens is capable of maintaining this response when iron is limiting to growth, whereas E. huxleyi is not. Differential expression between iron treatments further revealed specific genes used by each organism under low iron availability. Overall, these results highlight the responses of two dominant phytoplankton groups to upwelling cycles, providing insight into the mechanisms fueling diatom blooms during upwelling events. IMPORTANCE Coastal upwelling regions are among the most biologically productive ecosystems. During upwelling events, nutrient-rich water is delivered from depth resulting in intense phytoplankton blooms typically dominated by diatoms. Along with nutrients, phytoplankton may also be transported from depth to seed these blooms then return to depth as upwelling subsides creating a cycle with varied conditions. To investigate diatoms’ success in upwelling regions, we compare the responses of a common diatom and coccolithophore throughout simulated upwelling cycles under iron-replete and iron-limiting conditions. The diatom exhibited a distinct rapid response to upwelling irrespective of iron status, whereas the coccolithophore’s response was either delayed or suppressed depending on iron availability. Concurrently, the diatom highly expresses, or frontloads, nitrate assimilation genes prior to upwelling, potentially enabling this rapid response. These results provide insight into the molecular mechanisms underlying diatom blooms and ecological success in upwelling regions. 

Abstract While most models agree that the Atlantic meridional overturning circulation (AMOC) becomes weaker under greenhouse gas emission and is likely to weaken over the twenty-first century, they disagree on the projected magnitudes of AMOC weakening. In this work, CMIP6 models with stronger climatological AMOC are shown to project stronger AMOC weakening in both 1% ramping CO₂and abrupt CO₂quadrupling simulations. A physical interpretation of this result is developed. For models with stronger mean state AMOC, stratification in the upper Labrador Sea is weaker, allowing for stronger mixing of the surface buoyancy flux. In response to CO₂increase, surface warming is mixed to the deeper Labrador Sea in models with stronger upper-ocean mixing. This subsurface warming and corresponding density decrease drives AMOC weakening through advection from the Labrador Sea to the subtropics via the deep western boundary current. Time series analysis shows that most CMIP6 models agree that the decrease in subsurface Labrador Sea density leads AMOC weakening in the subtropics by several years. Also, idealized experiments conducted in an ocean-only model show that the subsurface warming over 500–1500 m in the Labrador Sea leads to stronger AMOC weakening several years later, while the warming that is too shallow (<500 m) or too deep (>1500 m) in the Labrador Sea causes little AMOC weakening. These results suggest that a better representation of mean state AMOC is necessary for narrowing the intermodel uncertainty of AMOC weakening to greenhouse gas emission and its corresponding impacts on future warming projections.