Spin current propagation through ultra-thin insulating layers in multilayered ferromagnetic systems

Spin current pumping from a ferromagnet through an insulating layer into a heavy metal was studied in a CoFeB/SiO2/Pt system in relation to the thickness and interfacial structure of the insulating layer. The propagation of spin current from the ferromagnet into the heavy metal falls rapidly with sub-nanometer thicknesses of SiO2 and is suppressed beyond a nominal thickness of 2 nm. Structural analysis shows that SiO2 only forms a complete barrier layer beyond around 2 nm, indicating that the presence of a discontinuous insulating barrier, and not tunneling or diffusion, explains the main observations of spin-pumping with thin insulating layers

Proximity-induced magnetism in Pt layered with rare-earth–transition-metal ferrimagnetic alloys

The proximity-induced moment (PIM) in heavy metal layers may play a significant role in heterostructured spintronic systems. In particular, the PIM of a heavy metal adjacent to a magnetic layer has been linked to interfacial spin transport behavior. Element-resolved x-ray magnetic measurements were used to investigate PIM in Pt layered with two different rare-earth (RE):3d transition-metal (TM) ferrimagnetic alloys in which the net moment was dominated by either the RE or the TM at room temperature. We observed significant PIM in Pt confined to a 2-nm interfacial region for Pt/Co77Gd23 and Pt/(Fe50Co50)77Gd23 and, in both cases, the PIM was parallel to the TM sublattice rather than the RE or the net moment. Our results highlight the prominence of the d−d mediated interactions between the Pt and the constituents of the ferrimagnetic RE:TM alloys over the net macroscopic moment

Magnetic damping in ferromagnetic/heavy-metal systems: The role of interfaces and the relation to proximity-induced magnetism

Damping and spin transport in spintronic multilayered systems continues to be a topic of active research. The enhancement of damping in ferromagnet (FM)/spacer layer (SL)/heavy-metal (HM) thin-film systems was studied for Co 25 Fe 75 / SL / Pt with a nonmagnetic (NM) SL of either Au or Cu with variable thickness, in order to understand the correlation with proximity-induced magnetism (PIM) in the HM. Structural, PIM and magnetic damping measurements were undertaken on the same samples. Specifically, secondary ion mass spectroscopy, element specific x-ray magnetic reflectivity and x-ray magnetic circular dichroism at the Pt and Au L 3 edges, and ferromagnetic resonance methods were used. With increasing thickness of a Cu or Au SL directly between the FM and the Pt layer, the Pt PIM and the damping both fall rapidly, with a relationship between damping and PIM that depends on the SL material. The PIM observed in the Au layer showed a complex dependence on the layer thickness, suggesting some hybridization with the Pt. The role of the number and location of interfaces on the damping was demonstrated with the addition of a SL within the Pt layer, which showed that the specific details of the NM/HM interface also affects the damping. The insertion of a Cu SL within the Pt showed a measurable increase in the overall enhancement of the damping while the insertion of a Au SL into Pt had almost no effect on the damping. Together these results demonstrate the role of both PIM and of additional interfaces in the enhancement of damping in FM/HM systems, which is not fully accounted for by existing theory

Proximity-induced magnetism in Pt layered with rare-earth–transition-metal ferrimagnetic alloys

The proximity-induced moment (PIM) in heavy metal layers may play a significant role in heterostructured spintronic systems. In particular, the PIM of a heavy metal adjacent to a magnetic layer has been linked to interfacial spin transport behavior. Element-resolved x-ray magnetic measurements were used to investigate PIM in Pt layered with two different rare-earth (RE): 3d transition-metal (TM) ferrimagnetic alloys in which the net moment was dominated by either the RE or the TM at room temperature. We observed significant PIM in Pt confined to a 2-nm interfacial region for Pt/Co77 Gd23 and Pt/(Fe50Co50)77 Gd23 and, in both cases, the PIM was parallel to the TM sublattice rather than the RE or the net moment. Our results highlight the prominence of the d−d mediated interactions between the Pt and the constituents of the ferrimagnetic RE:TM alloys over the net macroscopic moment

Switching the stereochemical outcome of 6-endo-trig cyclizations; Synthesis of 2,6-Cis-6-substituted 4-oxopipecolic acids

A base-mediated 6-endo-trig cyclization of readily accessible enone-derived α-amino acids has been developed for the direct synthesis of novel 2,6-cis-6- substituted-4-oxo-L-pipecolic acids. A range of aliphatic and aryl side chains were tolerated by this mild procedure to give the target compounds in good overall yields. Molecular modeling of the 6-endo-trig cyclization allowed some insight as to how these compounds were formed, with the enolate intermediate generated via an equilibrium process, followed by irreversible tautomerization/neutralization providing the driving force for product formation. Stereoselective reduction and deprotection of the resulting 2,6-cis-6-substituted 4-oxo-L-pipecolic acids to the corresponding 4-hydroxy-L-pipecolic acids was also performed

Non-uniform Gd distribution and magnetization profiles within GdCoFe alloy thin films

Rare earth (RE):transition metal (TM) ferrimagnetic alloys continue to attract significant attention for spintronics. This work focuses on the elemental distribution of RE and TM elements throughout the thickness of nominally uniform films and the resulting spatial variations of the magnetization within these layers. Samples of CoFe alloyed with Gd were studied using secondary ion mass spectroscopy, polarized neutron reflectometry, and x-ray resonant magnetic reflectivity. The samples were grown by magnetron co-sputtering to control the RE:TM alloy ratio of the ferrimagnetic layer, which was combined with W and Pt layers as either under or over-layers to create sample structures such as W/Gdx(Co70Fe30)100-x/Pt, wherex x=0,8, and 23 at. %. Results show that uniformly deposited thin-films have a significant variation in the distribution of the TM and RE through the film thickness, and this leads to a spatial distribution in the net magnetization profile and a non-uniform Gd magnetization profile within the layer. These findings have implications for the application RE:TM alloys in spintronics as they may impact the perpendicular magnetic anisotropy, the ferrimagnetic compensation temperature, and interfacial spin transport

Diagnosis and management of antiretroviral-therapy failure in resource-limited settings in sub-Saharan Africa: challenges and perspectives.

Despite the enormous progress made in scaling up antiretroviral therapy (ART) in sub-Saharan Africa, many challenges remain, not least of which are the identification and management of patients who have failed first-line therapy. Less than 3% of patients are receiving second-line treatment at present, whereas 15-25% of patients have detectable viral loads 12 months or more into treatment, of whom a substantial proportion might have virological failure. We discuss the reasons why virological ART failure is likely to be under-diagnosed in the routine health system, and address the current difficulties with standard recommended second-line ART regimens. The development of new diagnostic tools for ART failure, in particular a point-of-care HIV viral-load test, combined with simple and inexpensive second-line therapy, such as boosted protease-inhibitor monotherapy, could revolutionise the management of ART failure in resource-limited settings

A review of composite product data interoperability and product life-cycle management challenges in the composites industry

A review of composite product data interoperability and product life-cycle management challenges is presented, which addresses “Product Life-cycle Management”, developments in materials. The urgent need for this is illustrated by the life-cycle management issues faced in modern military aircraft, where in-service failure of composite parts is a problem, not just in terms of engineering understanding, but also in terms of the process for managing and maintaining the fleet. A demonstration of the use of ISO 10303-235 for a range of through-life composite product data is reported. The standardization of the digital representation of data can help businesses to automate data processing. With the development of new materials, the requirements for data information models for materials properties are evolving, and standardization drives transparency, improves the efficiency of data analysis, and enhances data accuracy. Current developments in Information Technology, such as big data analytics methodologies, have the potential to be highly transformative

A perspective on physical reservoir computing with nanomagnetic devices

Neural networks have revolutionized the area of artificial intelligence and introduced transformative applications to almost every scientific field and industry. However, this success comes at a great price; the energy requirements for training advanced models are unsustainable. One promising way to address this pressing issue is by developing low-energy neuromorphic hardware that directly supports the algorithm's requirements. The intrinsic non-volatility, non-linearity, and memory of spintronic devices make them appealing candidates for neuromorphic devices. Here, we focus on the reservoir computing paradigm, a recurrent network with a simple training algorithm suitable for computation with spintronic devices since they can provide the properties of non-linearity and memory. We review technologies and methods for developing neuromorphic spintronic devices and conclude with critical open issues to address before such devices become widely used