Optical Switching in Tb/Co-Multilayer Based Nanoscale Magnetic Tunnel Junctions

Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory devices. For high-speed and low-power data storage and processing applications, fast reversal by an ultrashort laser pulse is extremely important. We demonstrate optical switching of Tb/Comultilayer-based nanoscale MTJs by combining optical writing and electrical read-out methods. A 90 fs-long laser pulse switches the magnetization of the storage layer (SL). The change in magnetoresistance between the SL and a reference layer (RL) is probed electrically across the tunnel barrier. Single-shot switching is demonstrated by varying the cell diameter from 300 nm to 20 nm. The anisotropy, magnetostatic coupling, and switching probability exhibit cell-size dependence. By suitable association of laser fluence and magnetic field, successive commutation between high-resistance and low-resistance states is achieved. The switching dynamics in a continuous film is probed with the magneto-optical Kerr effect technique. Our experimental findings provide strong support for the growing interest in ultrafast spintronic devices.Comment: total pages 22, Total figure

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

A chemoenzymatic synthesis of the title compound has been developed using an efficient and highly enantioselective lipase-catalyzed acylation in a hydrophobic ionic liquid, [bmim][PF6], followed by a diastereoselective asymmetric dihydroxylation as the key steps for incorporating the stereogenic centers. The further conversion to the appropriate intermediates and subsequent acylation with lauric acid furnished the target compound

Progress toward picosecond on-chip magnetic memory

We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as a pathway to high-performance, energy-efficient, and non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such as spin-transfer-torque magnetic-resistive random-access memory (STT-MRAM) and spin-orbit torque MRAM, are promising due to their non-volatility, energy-efficiency, and high endurance. STT-MRAMs are now entering into the commercial market; however, they are limited in write speed to the nanosecond timescale. Improvement in the write speed of spintronic devices can significantly increase their usefulness as viable alternatives to the existing CMOS-based devices. In this article, we discuss recent studies that advance the field of ultrafast spintronics and opto-magnetism. An optimized ferromagnet-ferrimagnet exchange-coupled magnetic stack, which can serve as the free layer of a magnetic tunnel junction (MTJ), can be optically switched in as fast as ∼3 ps. Integration of ultrafast magnetic switching of a similar stack into an MTJ device has enabled electrical readout of the switched state using a relatively larger tunneling magnetoresistance ratio. Purely electronic ultrafast spin-orbit torque induced switching of a ferromagnet has been demonstrated using ∼6 ps long charge current pulses. We conclude our Perspective by discussing some of the challenges that remain to be addressed to accelerate ultrafast spintronics technologies toward practical implementation in high-performance digital information processing systems

Reactivity of nickel metal precursors towards amido linked <i>N</i>-heterocyclic carbenes and their catalytic studies for cross coupling reactions

The refluxing of chloroacetamide derivatives with n-butyl imidazole resulted in their corresponding salt of composition 1-(n-butyl)-3-N-(2-Ar)acetamido-1, 3-imidazolium chloride (Ar = furylmethyl (1a); phenylmethyl (1b)). The latter salt on treatment with DBU followed by the addition of chalcogen atom resulted into a compound [(1-(n-butyl)-3-N-(2-Ar)acetamido-1,3-imidazol-3-ylidine)E] (Ar = furylmethyl; E = S (2a); Ar = phenylmthyl; E = Se (2b)). Similarly, the reaction of the imidazolium salts with, excess K2CO3 and NiCl2·6H2O yielded compounds [(1-(n-butyl)-3-N-(2-Ar)acetamido-1,3-imidazol-3-ylidine)]2Ni (Ar = furylmethyl (3a); phenylmethyl (3b)). The latter complexes have also been isolated by using Ni(II) phosphine precursors [NiCl2(PP)] (PP = PPh3, dppf). The molecular structure of [(1-(n-butyl)-3-N-(2-furylmethyl)acetamido-1, 3-imidazol-3-ylidine)]2Ni and [(1-(n-butyl)-3-N-(2-phenylmethyl)acetamido-1, 3-imidazol-3-ylidine)]2Ni were established by single crystal X-ray diffraction analysis. The catalytic property of complex 3a and 3b for cross coupling reactions has been studied

Reactivity of nickel metal precursors towards amido linked N-heterocyclic carbenes and their catalytic studies for cross coupling reactions

One of the authors (RSC) is grateful to DST for the financial support under the DST young scientist scheme YSS/2014/000797.The refluxing of chloroacetamide derivatives with n-butyl imidazole resulted in their corresponding salt of composition 1-(n-butyl)-3-N-(2-Ar)acetamido-1, 3-imidazolium chloride (Ar = furylmethyl (1a); phenylmethyl (1b)). The latter salt on treatment with DBU followed by the addition of chalcogen atom resulted into a compound [(1-(n-butyl)-3-N-(2-Ar)acetamido-1,3-imidazol-3-ylidine)E] (Ar = furylmethyl; E = S (2a); Ar = phenylmthyl; E = Se (2b)). Similarly, the reaction of the imidazolium salts with, excess K2CO3 and NiCl2·6H2O yielded compounds [(1-(n-butyl)-3-N-(2-Ar)acetamido-1,3-imidazol-3-ylidine)]2Ni (Ar = furylmethyl (3a); phenylmethyl (3b)). The latter complexes have also been isolated by using Ni(II) phosphine precursors [NiCl2(PP)] (PP = PPh3, dppf). The molecular structure of [(1-(n-butyl)-3-N-(2-furylmethyl)acetamido-1, 3-imidazol-3-ylidine)]2Ni and [(1-(n-butyl)-3-N-(2-phenylmethyl)acetamido-1, 3-imidazol-3-ylidine)]2Ni were established by single crystal X-ray diffraction analysis. The catalytic property of complex 3a and 3b for cross coupling reactions has been studied.PostprintPeer reviewe

A Chemoenzymatic Synthesis of Hept-6-ene-2,5-diol Stereomers: Application to Asymmetric Synthesis of Decarestrictine L, Pyrenophorol, and Stagonolide E

The stereomers of hept-6-ene-2,5-diol derivatives were conceived as useful chiral intermediates and were synthesized starting from sulcatol using two lipase-catalyzed acylation reactions as the key steps. The versatility of the intermediates was demonstrated by converting them to the titled tetrahydropyran, macrolide, and macrodiolide compounds using standard synthetic protocols

Synthesis of palladium complexes derived from amido linked N-heterocyclic carbenes and their use in Suzuki cross coupling reactions

Treatment of 1-(n-butyl)-3-N-(2-Ar)acetamido-1, 3-imidazolium chloride (Ar=furylmethyl,phenylmethyl) with excess K2CO3 and [PdCl2(L−L)] (L−L=2 PPh3, dppf) afforded orange compounds of composition [(1-(n-butyl)-3-N-(2-Ar)acetamido-1,3-imidazol-2-ylidene)]2Pd (Ar=furylmethyl; phenylmethyl). These complexes were characterized by NMR (1H and 13C{1H} NMR), IR and micro-analysis data. Subsequently, the catalytic efficiency of these complexes for cross coupling reactions between 4-haloarenens (halo=Br, I) and phenylboronic acid was studied under different solvents (acetonitrile, THF and DMF), temperatures with different catalyst loadings. The molecular structure of [(1-(n-butyl)-3-N-(2-furylmethyl)acetamido-1, 3-imidazol-2-ylidene)]2Pd was established by single crystal X-ray diffraction analysis

Impact of water addition on fluctuation dynamics in viscous solvents with varied heterogeneity: A 2D IR spectroscopic study

The addition of cosolvent, such as water, influences the overall fluctuation dynamics as sensed by the probe. It is crucial to unravel the fluctuation dynamics when water is added, particularly in viscous solvents with varying degrees of heterogeneity. In this study, we employed two-dimensional infrared spectroscopy to examine the solvation dynamics of two viscous solvents: glycerol, a molecular solvent, and malicine, an acid-based deep eutectic solvent. Additionally, we explored the relative changes in fluctuation dynamics upon water addition. Our results indicate that water disrupts the hydrogen bond network in glycerol, but no significant effect is observed in malicine. Our experimental findings align well with previously reported simulation studies