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Abstract Cr_xPt_1−xTe₂is a recently developed van der Waals magnetic alloy noted for its stability under ambient conditions. Here, we report the emergence of an exchange bias effect in Cr_xPt_1−xTe₂, without typical exchange bias sources such as an adjacent antiferromagnetic layer. We find that the exchange bias is present forx = 0.45 and absent forx = 0.35, which is correlated to the presence of a Cr modulation where the Cr concentration alternates each vdW layer (modulation period of 2 layers) forx ≥ 0.4. We perform Monte Carlo simulations utilizing exchange parameters from first-principles calculations, which recreate the exchange bias in hysteresis loops of Cr_0.45Pt_0.55Te₂. From our simulations, we infer the source of exchange bias to be magnetic moments locked into free energy minima that resist magnetization reversal. This work presents a way to introduce desirable magnetic properties to van der Waals magnets. 

Kagome lattices have garnered substantial interest because their band structure consists of topological flat bands and Dirac cones. The RMn6Sn6 (R = rare earth) compounds are particularly interesting because of the existence of the large intrinsic anomalous Hall effect (AHE), which originates from the gapped Dirac cones near the Fermi level. This makes RMn6Sn6 an outstanding candidate for realizing the high-temperature quantum AHE. The growth of RMn6Sn6 thin films is beneficial for both fundamental research and potential applications. However, most of the studies on RMn6Sn6 have focused on bulk crystals, and the synthesis of RMn6Sn6 thin films has not been reported so far. Here, we report the atomic layer molecular beam epitaxy growth, structural and magnetic characterizations, and transport properties of ErMn6Sn6 and TbMn6Sn6 thin films. It is especially noteworthy that TbMn6Sn6 thin films have out-of-plane magnetic anisotropy, which is important for realizing the quantum AHE. Our work paves the avenue toward the control of the AHE using devices patterned from RMn6Sn6 thin films. 

One of the most fundamental goals of modern biology is to achieve a deep understanding of the origin and maintenance of biodiversity. It has been observed that in some mixed-species animal societies, there appears to be a drive towards some degree of phenotypic trait matching, such as similar coloration or patterning. Here we build on these observations and hypothesize that selection in mixed-species animal societies, such as mixed-species bird flocks, may drive diversification, potentially leading to speciation. We review evidence for possible convergent evolution and even outright mimicry in flocks from southwestern China, where we have observed several cases in which species and subspecies differ from their closest relatives in traits that match particular flock types. However, understanding whether this is phenotypic matching driven by convergence, and whether this divergence has promoted biodiversity, requires testing multiple facets of this hypothesis. We propose a series of steps that can be used to tease apart alternative hypotheses to build our understanding of the potential role of convergence in diversification in participants of mixed-species societies. Even if our social convergence/divergence hypothesis is not supported, the testing at each step should help highlight alternative processes that may affect mixed-species flocks, trait evolution and possible convergence. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’. 

The urgency for remote, reliable and scalable biodiversity monitoring amidst mounting human pressures on ecosystems has sparked worldwide interest in Passive Acoustic Monitoring (PAM), which can track life underwater and on land. However, we lack a unified methodology to report this sampling effort and a comprehensive overview of PAM coverage to gauge its potential as a global research and monitoring tool. To address this gap, we created the Worldwide Soundscapes project, a collaborative network and growing database comprising metadata from 416 datasets across all realms (terrestrial, marine, freshwater and subterranean).