Electrical control of metallic heavy-metal/ferromagnet interfacial states

Voltage control effects provide an energy-efficient means of tailoring material properties, especially in highly integrated nanoscale devices. However, only insulating and semiconducting systems can be controlled so far. In metallic systems, there is no electric field due to electron screening effects and thus no such control effect exists. Here we demonstrate that metallic systems can also be controlled electrically through ionic not electronic effects. In a Pt/Co structure, the control of the metallic Pt/Co interface can lead to unprecedented control effects on the magnetic properties of the entire structure. Consequently, the magnetization and perpendicular magnetic anisotropy of the Co layer can be independently manipulated to any desired state, the efficient spin toques can be enhanced about 3.5 times, and the switching current can be reduced about one order of magnitude. This ability to control a metallic system may be extended to control other physical phenomena.Comment: 20 pages, 7 figures, Accepted by Physical Review Applied (2017

Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy

Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Neel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems

Left and right ventricular myocardial deformation and late gadolinium enhancement:incremental prognostic value in amyloid light-chain amyloidosis

Background: Previous cardiac magnetic resonance (CMR) studies have shown that both late gadolinium enhancement (LGE) and left ventricular (LV) strain have prognostic value in amyloid light-chain (AL) amyloidosis, but the right ventricular (RV) strain has not yet been studied. We aim to determine the incremental prognostic value of LV and RV LGE and strain in AL amyloidosis. Methods: This prospective study recruited 87 patients (age, 56.9 +/- 9.1 years; M/F, 56/31) and 20 healthy subjects (age, 52.7 +/- 8.1 years; M/F, 11/9) who underwent CMR. The LV LGE was classified into no, patchy and global groups. The RV LGE was classified into negative and positive groups. Myocardial deformation was measured using a dedicated software. Follow-up was performed for all-cause mortality using Cox proportional hazards regression and Kaplan-Meier curves. Results: During a median follow-up of 21 months, 34 deaths occurred. Presence of LV LGE [HR 2.44, 95% confidence interval (CI), 1.10-5.45, P=0.029] and global longitudinal strain (GLS) (HR 1.13 per 1% absolute decrease, 95% CI, 1.02-1.25, P=0.025) were independent LV predictors. RV LGE (HR 4.07, 95% CI, 1.09-15.24, P=0.037) and GLS (HR 1.10 per 1% absolute decrease, 95% CI, 1.00-1.21, P=0.047) were independent RV predictors. Complementary to LV LGE, LV GLS impairment or RV LGE further reduced survival (both log rank P Conclusions: This study confirms the incremental prognostic value of LV GLS and RV LGE in AL amyloidosis, which refines the conventional risk evaluation based on LV LGE. GLS based on non-contrast-enhanced CMR are promising new predictors

Comparing Day 5 versus Day 6 euploid blastocyst in frozen embryo transfer and developing a predictive model for optimizing outcomes: a retrospective cohort study

BackgroundOptimal protocols for frozen-thawed embryo transfer (FET) after preimplantation genetic testing (PGT) remain unclear. This study compared Day 5 (D5) and Day 6 (D6) blastocysts and evaluated predictors of FET success.MethodsA total of 870 patients with genetic diseases or chromosomal translocations who received PGT at the First Affiliated Hospital of Zhengzhou University from January 2015 to December 2019 were recruited. All patients underwent at least one year of follow-up. Patients were divided into groups according to the blastocyst development days and quality. Univariate and multivariate logistic regression were applied to identify risk factors that affect clinical outcomes and to construct a predictive nomogram model. Area under the curve (AUC) of the subject’s operating characteristic curve and GiViTI calibration belt were conducted to determine the discrimination and fit of the model.ResultsD5 blastocysts, especially high-quality D5, resulted in significantly higher clinical pregnancy (58.4% vs 49.2%) and live birth rates (52.5% vs 45%) compared to D6. Multivariate regression demonstrated the number of blastocysts, endometrial preparation protocol, days of embryonic development and the quality of blastocysts independently affected live birth rates (P<0.05). A nomogram integrating these factors indicated favorable predictive accuracy (AUC=0.598) and fit (GiViTI, P=0.192).ConclusionsTransferring high-quality D5 euploid blastocysts after PGT maximizes pregnancy outcomes. Blastocyst quality, blastocyst development days, endometrial preparation protocols, and number of blastocysts, independently predicted outcomes. An individualized predictive model integrating these factors displayed favorable accuracy for counseling patients and optimizing clinical management

Tm3Fe5O12/Pt Heterostructures with Perpendicular Magnetic Anisotropy for Spintronic Applications

With recent developments in the field of spintronics, ferromagnetic insulator (FMI) thin films have emerged as an important component of spintronic devices. Ferrimagnetic yttrium iron garnet in particular is an excellent insulator with low Gilbert damping and a Curie temperature well above room temperature, and has been incorporated into heterostructures that exhibit a plethora of spintronic phenomena including spin pumping, spin Seebeck, and proximity effects. However, it has been a challenge to develop high quality sub-10 nm thickness FMI garnet films with perpendicular magnetic anisotropy (PMA) and PMA garnet/heavy metal heterostructures to facilitate advances in spin-current and anomalous Hall phenomena. Here, robust PMA in ultrathin thulium iron garnet (TmIG) films of high structural quality down to a thickness of 5.6 nm are demonstrated, which retain a saturation magnetization close to bulk. It is shown that TmIG/Pt bilayers exhibit a large spin Hall magnetoresistance (SMR) and SMR-driven anomalous Hall effect, which indicates efficient spin transmission across the TmIG/Pt interface. These measurements are used to quantify the interfacial spin mixing conductance in TmIG/Pt and the temperature-dependent PMA of the TmIG thin film

Structure Study of Magnetic Thin Films for Voltage Controlled Spintronics by Scanning Transmission Electron Microscopy Experiment and Density Functional Theory Calculations

We have studied magnetic thin films for voltage controlled magnetic tunnel junctions (MTJs) by advanced scanning transmission electron microscopy (STEM) and density functional theory (DFT) simulations. MTJs are the prototypical spintronic device and manipulation of magnetism by electrical means is among the most promising approaches to novel voltage-controlled spin electronics. Compared with the present metal-oxide-semiconductor devices, voltage-controlled spintronics have great advantage of reducing power consumption and enhancing processing speed. The voltage controlled magnetic effect can be achieved across many different materials systems, such as voltage-induced magnetization phase transitions, electric-field control of coercivity and electric control of magnetic anisotropy, all of which depend on high-quality thin films with minimum crystallographic defects. Cr2O3 is antiferromagnetic in bulk but ferromagnetic on the (0001) surface. Bulk Cr2O3 has two degenerate antiferromagnetic states with opposite (0001) surface spin polarization. As Cr2O3 is also magnetoelectric, the degenerate antiferromagnetic states can be lifted by manipulating the free-energy gain ΔF=aEH. Therefore, the surface ferromagnetism can be controlled by changing the sign of applied electric field. Compared with bulk Cr2O3, high leakage current, low breakdown voltage, low magnetic ordering temperature and high EH products to observe magnetoelectric effect are commonly observed in Cr2O3 thin films. Hence, it is essential to understand the film microstructure and its relationship to the substrate conditions. We have observed vertical grain boundaries in Cr2O3/Al2O3 systems that are related with a 60 in-plane rotation by diffraction contrast TEM image. STEM as a function of scattering angle points out a simultaneous 1⁄3[101 ̅0] basal plane shift. Local boundary electron energy loss spectroscopy (EELS) shows a pre-peak on the O K-edge arising from unoccupied O 2p states, indicating a reduced bandgap along the boundary that provides potential breakdown paths in Cr2O3 thin films. B doping of Cr2O3 is known to increase the Néel temperature. B was found to form either BCr4 tetrahedra or BO3 triangles in the Cr2O3 lattice, with σ^* and π^* bonds exhibiting different energy loss features. Modeling the experimental spectra as a linear combination of simulated B K edges reproduces the experimental π^* / σ^* ratios for 12 to 43 % of the B in the sample occupying BCr4 sites. Simulated BCr4 fraction / total B as a function of oxygen partial pressures supports the EELS results and indicates further increase of Néel temperature can be achieved by optimizing oxygen partial pressures. We also investigated the GdOx/Co/Pt systems, in which the voltage effect comes from the oxygen migration through the Co layer to the Co/Pt interface. Hybridization between O 2p and Co 3d states modifies the energy of Co 3d orbitals, introducing crystal field effects that favor 3d orbital anisotropy. STEM EELS were performed to study spatial oxidization heterogeneity by voltage-induced oxygen migration in 4 nm Co films that results in tunable perpendicular. Depth profiles of oxygen migration under applied voltage histories, as well as the structural origin of perpendicular magnetic anisotropy (PMA) is revealed. Particularly, an intermediate PMA state was achieved by a combination of negative and positive voltages, with residual CoOx at Pt/Co interface and abrupt oxygen concentration boundary in the Co layer.  C-SPIN Starnet Center, supported by SRC and DARP

Impact of Process Technology on Properties of Large-Scale Wind Turbine Blade Composite Spar Cap

As wind turbine blade length increases, reconciling lightweight design with strength necessitates continuous advancements in process technology. The impact of three different process technologies–vacuum-assisted resin transfer moulding (VARTM), prepreg, and pultrusion–on the properties of wind turbine blade composite spar caps was investigated using scanning electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and static and fatigue testing. The results demonstrated that the fibre weight content and 0° tensile modulus of the VARTM and pultrusion composites increased as compared to those of the prepreg samples. Subsequently, the properties of a 94-m blade were analysed using the Ansys Composite PrepPost (ACP) and static structure modules in Ansys simulations, and the weights of the spar cap were compared with test data of materials under different process technologies. The results showed that the masses of the spar cap of a 94-m blade in the pultrusion, VARTM, and prepreg processes were 7965, 9170, and 9942 kg, respectively. The quantitative influence rules on the weight of the wind turbine blade spar cap prepared through different process technologies were formulated. The findings of this study are promising and are expected to aid the development of wind turbine blade process technologies

Conditional Deletion of <i>Foxg1</i> Delayed Myelination during Early Postnatal Brain Development

FOXG1 (forkhead box G1) syndrome is a neurodevelopmental disorder caused by variants in the Foxg1 gene that affect brain structure and function. Individuals affected by FOXG1 syndrome frequently exhibit delayed myelination in neuroimaging studies, which may impair the rapid conduction of nerve impulses. To date, the specific effects of FOXG1 on oligodendrocyte lineage progression and myelination during early postnatal development remain unclear. Here, we investigated the effects of Foxg1 deficiency on myelin development in the mouse brain by conditional deletion of Foxg1 in neural progenitors using NestinCreER;Foxg1fl/fl mice and tamoxifen induction at postnatal day 0 (P0). We found that Foxg1 deficiency resulted in a transient delay in myelination, evidenced by decreased myelin formation within the first two weeks after birth, but ultimately recovered to the control levels by P30. We also found that Foxg1 deletion prevented the timely attenuation of platelet-derived growth factor receptor alpha (PDGFRα) signaling and reduced the cell cycle exit of oligodendrocyte precursor cells (OPCs), leading to their excessive proliferation and delayed maturation. Additionally, Foxg1 deletion increased the expression of Hes5, a myelin formation inhibitor, as well as Olig2 and Sox10, two promoters of OPC differentiation. Our results reveal the important role of Foxg1 in myelin development and provide new clues for further exploring the pathological mechanisms of FOXG1 syndrome