Spin-orbit torque induced dipole skyrmion motion at room temperature

We demonstrate deterministic control of dipole-field-stabilized skyrmions by means of spin-orbit torques arising from heavy transition-metal seed layers. Experiments are performed on amorphous Fe/Gd multilayers that are patterned into wires and exhibit stripe domains and dipole skyrmions at room temperature. We show that while the domain walls and skyrmions are achiral on average due to lack of Dzyaloshinskii-Moriya interactions, the N\'eel-like closure domain walls at each surface are chiral and can couple to spin-orbit torques. The current-induced domain evolutions are reported for different magnetic phases, including disordered stripe domains, coexisting stripes and dipole skyrmions and a closed packed dipole skyrmion lattice. The magnetic textures exhibit motion under current excitations with a current density ~10^8 A/m2. By comparing the motion resulting from magnetic spin textures in Fe/Gd films with different heavy transition-metal interfaces, we confirm spin currents can be used to manipulate achiral dipole skyrmions via spin-orbit torques.Comment: 23 pages, 8 figure

Lived Experience of the Mother's Caring of Adult Children with Persistent Vegetative State

PURPOSE: The purpose of this study was to deepen understanding the nature of the care experience by the mothers with adult children in persistent vegetative state. METHODS: Participants were 7 mothers caring for their adult children in persistent vegetative state. Data were collected individually through in-depth interviews on their lived experiences. Also texts were included as data from literary works, novels, movies, essays, and arts containing on patients with persistent vegetative state and their mothers. Data were analyzed by van Manen's phenomenological methodology. RESULTS: The essential themes of caring experiences of the mothers were as follows. The theme in relation to lived time has shown as back to the past and caring experience related lived body has emerged as locked the body in children. The theme related lived space was getting into the swamp and the theme in lived others was derived as lonely struggle into. CONCLUSION: The nature of mothers' caring experiences for adult children in persistent vegetative state is summarized as ‘Do not off hand of hope in a locked state’. This study suggests long-term supports are necessary for mothers to care persistent vegetative state children

Energy-efficient generation of skyrmion phases in Co/Ni/Pt-based multilayers using Joule heating

We have studied the effects of electrical current pulses on skyrmion formation in a series of Co/Ni/Pt-based multilayers. Transmission X-ray microscopy reveals that by applying electrical current pulses of duration and current density on the order of $\tau$=50 $\mu$s and j=1.7x10$^1$$^0$ A/m$^2$, respectively, in an applied magnetic field of $\mu$$_0$Hz=50 mT, stripe-to-skyrmion transformations are attained. The skyrmions remain stable across a wide range of magnetic fields, including zero field. The skyrmions then remain stable across a wide range of magnetic fields, including zero field. We primarily attribute the transformation to current-induced Joule heating on the order of ~125 K. Reducing the magnetic moment and perpendicular anisotropy using thin rare-earth spacers dramatically reduces the pulse duration, current density, and magnetic field necessary to 25 $\mu$s, 2.4x10$^9$ A/m$^2$, and 27 mT, respectively. These findings show that energetic inputs allow for the formation of skyrmion phases in a broad class of materials and that material properties can be tuned to yield more energy-efficient access to skyrmion phases.Comment: 32 pages, 7 figures, 9 supplemental figure

X-ray imaging of vortex cores in confined magnetic structures

Cores of magnetic vortices in micron-sized NiFe disk structures, with thicknesses between 150 and 50 nm, were imaged and analysed by high resolution magnetic soft X-ray microscopy. A decrease of the vortex core radius was observed, from #24; ~38 to 18 nm with decreasing disk thickness. By comparing with full 3D micromagnetic simulations showing the well-known barrel structure, we obtained excellent agreement taking into account instrumental broadening and a small perpendicular anisotropy. The proven magnetic spatial resolution of better than 25 nm was sufficient to identify a negative dip close to the vortex core, originating from stray fields of the core. Magnetic vortex structures can serve as test objects for evaluating sensitivity and spatial resolution of advanced magnetic microscopy techniques

Gender Based Health Inequality and Impacting Factors

PURPOSE: This study was aimed to identify gender-based health inequality and explore impacting factors on health inequality in one province in Korea. METHODS: This was an explanatory study using the secondary data on Chungnam province from the Fifth Community Health Survey from August 16 to Oct 31, 2012. Variables included in this analysis were education level, poverty, marital status, and residential community for socio-cultural characteristics and subjective health status as an indicator of health inequality. Data were analyzed by chi2-test, t-test, ANOVA, and multiple linear regression. RESULTS: There were gender inequalities and disparities in health, and these inequalities were greater in woman than in man (chi2=161.8, p<.001). The impacting factors were education level, poverty, marital status, and residential community, which was accounted for 22.6% of variances of health inequality. Among these variables, gender showed the largest influence in health inequalities. CONCLUSION: To solve health inequalities, it should be considered gender differences based on social determinants of health. It is necessary to develop long term project based on these results and the social determinants model of World Health Organization

Direct observation of stochastic domain-wall depinning in magnetic nanowires

The stochastic field-driven depinning of a domain wall pinned at a notch in a magnetic nanowire is directly observed using magnetic X-ray microscopy with high lateral resolution down to 15 nm. The depinning-field distribution in Ni{sub 80}Fe{sub 20} nanowires considerably depends on the wire width and the notch depth. The difference in the multiplicity of domain-wall types generated in the vicinity of a notch is responsible for the observed dependence of the stochastic nature of the domain wall depinning field on the wire width and the notch depth. Thus the random nature of the domain wall depinning process is controllable by an appropriate design of the nanowire

Probing the spin polarization of current by soft X-ray imaging of current-induced magnetic vortex dynamics

Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micronsized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 +/-0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.Comment: 13 pages, 3 figure

Sub-nanosecond signal propagation in anisotropy engineered nanomagnetic logic chains

Energy efficient nanomagnetic logic (NML) computing architectures propagate and process binary information by relying on dipolar field coupling to reorient closely-spaced nanoscale magnets. Signal propagation in nanomagnet chains of various sizes, shapes, and magnetic orientations has been previously characterized by static magnetic imaging experiments with low-speed adiabatic operation; however the mechanisms which determine the final state and their reproducibility over millions of cycles in high-speed operation (sub-ns time scale) have yet to be experimentally investigated. Monitoring NML operation at its ultimate intrinsic speed reveals features undetectable by conventional static imaging including individual nanomagnetic switching events and systematic error nucleation during signal propagation. Here, we present a new study of NML operation in a high speed regime at fast repetition rates. We perform direct imaging of digital signal propagation in permalloy nanomagnet chains with varying degrees of shape-engineered biaxial anisotropy using full-field magnetic soft x-ray transmission microscopy after applying single nanosecond magnetic field pulses. Further, we use time-resolved magnetic photo-emission electron microscopy to evaluate the sub-nanosecond dipolar coupling signal propagation dynamics in optimized chains with 100 ps time resolution as they are cycled with nanosecond field pulses at a rate of 3 MHz. An intrinsic switching time of 100 ps per magnet is observed. These experiments, and accompanying macro-spin and micromagnetic simulations, reveal the underlying physics of NML architectures repetitively operated on nanosecond timescales and identify relevant engineering parameters to optimize performance and reliability.Comment: Main article (22 pages, 4 figures), Supplementary info (11 pages, 5 sections