Magnetization switching by the interaction between spins and charges has greatly brightened the future of spintronic memories. [1][2][3][4][5][6] This has been evident in the rapid development of spin transfer torque-magnetic random-access memory (STT-MRAM) as a mainstream non-volatile memory technology, in which a spin-polarized current is injected into magnetic tunnel junctions (MTJs) for cell programming. 7-18 However, as cell areas scale down to meet density and power demands, conventional STT-MRAM suffers from serious endurance and reliability issues due to the aging of the ultrathin MgO barrier and read disturbance. The challenge of lowering STT switching current densities to further reduce power consumption is still yet to be met. [19][20][21] The discovery of spin-orbit torque (SOT) switching in heavy metal/ferromagnetic metal/oxide heterostructures by applying an in-plane charge current to three-terminal devices provides a promising alternative mechanism. 22-28 It shows the potential to enhance the endurance and reliability of MRAM, while improving speed and reducing power consumption. [29][30][31][32] Thus, considerable research has been triggered to further elucidate the mechanism of SOT switching, which is currently described as magnetic reversal via two vector components, the damping-like (DL) and field-like (FL) torques. 33,34 Since the demonstration of perpendicular-anisotropy MgO/CoFeB MTJs (p-MTJs), the switching of perpendicular magnetization by SOT has become of particular interest. [33][34][35][36][37][38] However, an external magnetic field collinear with the charge current is required to execute deterministic switching of p-MTJs. This intrinsic constraint, combined with the three-terminal device configuration, is limiting the practical application of SOT-MRAM. [26][27][28]35 Great efforts have been made to eliminate the need

Perpendicular magnetic tunnel junctions based on MgO/CoFeB structures are of particular interest for magnetic random-access memories because of their excellent thermal stability, scaling potential, and power dissipation. However, the major challenge of current-induced switching in the nanopillars with both a large tunnel magnetoresistance ratio and a low junction resistance is still to be met. Here, we report spin transfer torque switching in nano-scale perpendicular magnetic tunnel junctions with a magnetoresistance ratio up to 249% and a resistance area product as low as 7.0 Ω µm2, which consists of atom-thick W layers and double MgO/CoFeB interfaces. The efficient resonant tunnelling transmission induced by the atom-thick W layers could contribute to the larger magnetoresistance ratio than conventional structures with Ta layers, in addition to the robustness of W layers against high-temperature diffusion during annealing. The critical switching current density could be lower than 3.0 MA cm−2 for devices with a 45-nm radius.

Migraine is a common recurrent neurological disorder combining nausea, vomiting, and hypersensitivities to visual, auditory, olfactory and somatosensory stimuli. However, the dysfunction of the sensorimotor network in migraineurs has not been well clarified. In the present study, we evaluated the dysfunction of the sensorimotor network in 30 migraineurs without aura and in 31 controls by combining regional homogeneity (ReHo), amplitudes of low-frequency fluctuation (ALFF) and degree centrality (DC) analysis methods based on resting-state fMRI. A seed-based functional connectivity (FC) analysis was used to investigate whether the dysfunctional areas within the sensorimotor network exhibited abnormal FC with other brain areas. Compared to the controls, the migraineurs without aura exhibited significantly smaller ReHo, ALFF and DC values in the primary somatosensory cortex (S1) and right premotor cortex (PMC). The migraineurs showed weaker FC between the S1 and brain areas within the pain intensity and spatial discrimination pathways and trigemino-thalamo-cortical nociceptive pathway. We proposed that the dysfunction of the S1 and PMC and the decreased FC between the S1 and brain areas in migraineurs without aura may disrupt the discrimination of sensory features of pain and affect nociception pathways, and would be involved in the dysfunctional mechanism in migraine.

Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

BackgroundMigraine constitute a disorder characterized by recurrent headaches, and have a high prevalence, a high socio-economic burden and severe effects on quality of life. Our previous fMRI study demonstrated that some brain regions are functional alterations in migraineurs. As the function of the human brain is related to its structure, we further investigated white and gray matter structural alterations in migraineurs.MethodsIn current study, we used surface-based morphometry, voxel-based morphometry and diffusion tensor imaging analyses to detect structural alterations of the white matter and gray matter in 32 migraineurs without aura compared with 32 age- and gender-matched healthy controls.ResultsWe found that migraineurs without aura exhibited significantly increased gray matter volume in the bilateral cerebellar culmen, increased cortical thickness in the lateral occipital-temporal cortex, decreased cortical thickness in the right insula, increased gyrification index in left postcentral gyrus, superior parietal lobule and right lateral occipital cortex, and decreased gyrification index in the left rostral middle frontal gyrus compared with controls. No significant change in white matter microstructure was found in DTI analyses.ConclusionThe significantly altered gray matter brain regions were known to be associated with sensory discrimination of pain, multi-sensory integration and nociceptive information processing and were consistent with our previous fMRI study, and may be involved in the pathological mechanism of migraine without aura.