Due to its inherent superior perpendicular magnetocrystalline anisotropy, the FePt in L10 phase enables magnetic storage and memory devices with ultrahigh capacity. However, reversing the FePt magnetic state, and therefore encoding information, has proven to be extremely difficult. Here, it is demonstrated that an electric current can exert a large spin torque on an L10 FePt magnet, ultimately leading to reversible magnetization switching. The spin torque monotonically increases with increasing FePt thickness, exhibiting a bulk characteristic. Meanwhile, the spin torque effective fields and switching efficiency increase as the FePt approaches higher chemical ordering with stronger spin–orbit coupling. The symmetry breaking that generates spin torque within L10 FePt is shown to arise from an inherent structural gradient along the film normal direction. By artificially reversing the structural gradient, an opposite spin torque effect in L10 FePt is demonstrated. At last, the role of the disorder gradient in generating a substantial torque in a single ferromagnet is supported by theoretical calculations. These results will push forward the frontier of material systems for generating spin torques and will have a transformative impact on magnetic storage and spin memory devices with simple architecture, ultrahigh density, and readily application.

An unprecedented ligand-controlled regiodivergent Cu(I)-catalyzed asymmetric intermolecular (3 + 2) cycloaddition reaction of α-substituted iminoesters with β-fluoromethyl β,β-disubstituted enones was developed. This novel strategy provides an efficient method for the enantioselective regiodivergent synthesis of pyrrolidines bearing two adjacent quaternary stereocenters or two discrete quaternary stereocenters, opening up a new era for medicinal chemistry and diversity-oriented synthesis. DFT calculations showed that the P,N-ligand L2 acts as a pseudobidentate ligand. The formation of a O-Cu bond with the carbonyl oxygen atom of the enone and dissociation of the amine nitrogen of L2 from the Cu(I) center occurs during the catalytic cycle; this is the main reason for the tuning the regioselectivity of the cycloaddition reaction caused by switching of the ligand. The salient features of this work include high yields (up to >99%), a general substrate scope, the use of commercially available ligands, and high regio-(up to >20:1 rr), diastereo- (up to >20:1 dr), and enantioselectivity (up to >99% ee).

In transport, the topological Hall effect (THE) presents itself as nonmonotonic features (or humps and dips) in the Hall signal and is widely interpreted as a sign of chiral spin textures, like magnetic skyrmions. However, when the anomalous Hall effect (AHE) is also present, the coexistence of two AHEs could give rise to similar artifacts, making it difficult to distinguish between genuine THE with AHE and two-component AHE. Here, we confirm genuine THE with AHE by means of transport and magneto-optical Kerr effect (MOKE) microscopy, in which magnetic skyrmions are directly observed, and find that genuine THE occurs in the transition region of the AHE. In sharp contrast, the artifact “THE” or two-component AHE occurs well beyond the saturation of the “AHE component” (under the false assumption of THE + AHE). Furthermore, we distinguish artifact “THE” from genuine THE by three methods: (1) minor loops, (2) temperature dependence, and (3) gate dependence. Minor loops of genuine THE with AHE are always within the full loop, while minor loops of the artifact “THE” may reveal a single loop that cannot fit into the “AHE component”. In addition, the temperature or gate dependence of the artifact “THE” may also be accompanied by a polarity change of the “AHE component”, as the nonmonotonic features vanish, while the temperature dependence of genuine THE with AHE reveals no such change. Our work may help future researchers to exercise caution and use these methods for careful examination in order to ascertain the genuine THE.

Reported herein is an asymmetric [3+2] cycloaddition reaction of azomethine ylides with β-trifluoromethyl β,β-disubstituted enones, a reaction which is enabled by a Ming-Phos-derived copper(I) catalyst (Ming-Phos=chiral sulfinamide monophosphines, Figure ). This method provides scalable and efficient access to the highly substituted pyrrolidines with a trifluoromethylated, all-carbon quaternary stereocenter in good yields with up to greater than 20:1 d.r. and 98 % ee. The reaction has a broad substrate scope and tolerates a wide range of functional groups.

Summary In this paper, we propose a simulation model to study real‐world replication workflows for cloud storage systems. With this model, we present three new methods to maximize the storage space usage during replica creation, and two novel QoS aware greedy algorithms for replica placement optimization. By using a simulation method, our algorithms are evaluated, through a comparison with the existing placement algorithms, to show that (i) a more evenly distributed replicas for a data set can be achieved by using round‐robin methods in replica creation phase and (ii) the two proposed greedy algorithms, named GS_QoS and GS_QoS_C1, not only have more economical results than those from Chen et al., but also guarantee the QoS for clients. Copyright © 2016 John Wiley & Sons, Ltd.

The employment of β,β-disubstituted enones as dipolarophiles poses a considerable challenge due to their steric hindrance and low reactivity. A copper-catalyzed asymmetric exo-selective dipolar cycloaddition of β-trifluoromethyl β,β-disubstituted enones with azomethine ylides was developed, which provides an efficient access to valuable pyrrolidines bearing a trifluoromethylated all-carbon quaternary stereocenter. Up to quantitative yields with up to >20 : 1 dr and 99% ee were delivered. A broad substrate scope, good functional group tolerance, high stereoselectivity, as well as diverse synthetically valuable transformations of the products make this approach highly attractive.

The employment of α-trifluoromethyl α,β-unsaturated esters as dipolarophiles pose considerable challenge due to expeditious defluorination and intrinsic steric hindrance. The present work provides an efficient access to valuable pyrrolidines bearing a trifluoromethylated all-carbon quaternary stereocenter through copper/M7-catalyzed asymmetric dipolar cycloaddition of α-trifluoromethyl α,β-unsaturated esters with azomethine ylides. The products were obtained in up to 98% yield with up to >20:1 d.r. and 99% ee. A broad substrate scope, good functional group tolerance, high stereoselectivity, as well as diverse synthetically valuable transformations of the products make this approach highly attractive.

No abstract