Domain wall pinning and potential landscapes created by constrictions and protrusions in ferromagnetic nanowires

The potential experienced by transverse domain walls (TDWs) in the vicinity of asymmetric constrictions or protrusions in thin Permalloy nanowires is probed using spatially resolved magneto-optical Kerr effect measurements. Both types of traps are found to act as pinning centers for DWs. The strength of pinning is found to depend on the trap type as well as on the chirality of the incoming DW; both types of traps are seen to act either as potential wells or potential barriers, also depending on the chirality of the DW. Micromagnetic simulations have been performed that are in good qualitative agreement with the experimental results.Comment: 6 pages, 7 figure

A qualitative exploration of English black adults’ views of strength and balance activities in mid-life

BACKGROUND: Public health guidelines state that all adults should undertake muscle and bone strengthening and balance training activities at least twice a week to support their physical function and maintain independent health. This is intended to maintain strength in adulthood and offset natural declines in bone density and muscle mass. Most older adults do not meet this guideline with low levels of compliance among older black people. This study explored the experiences of physical activity relating to strength and balance activities, amongst black men and women living in England, aged 50–70. METHODS: Participants were recruited by phone via a network of research recruitment specialists across England. In-depth qualitative interviews were conducted with 25 black people aged 50–70 living in England. An inductive thematic analysis was conducted. RESULTS: We found there was only a very general understanding of the importance of maintaining body strength and balance, and low salience: strength and balance activities were not seen to be an important part of participants’ lives. Most participants only wanted to be strong enough to get on with ‘normal life’ and not to build strength or balance. Participants aged 50–70 were likely to think they were too young to worry about strength and balance, which tended to be mentioned only if someone had experienced a problem. Participants reported that NHS staff, especially physiotherapists are a key source of information on the topic and could therefore be useful in future prevention strategies. CONCLUSION: Public health recommendations stress the importance of increasing participation in regular strength and balance activities as people age, to reduce the risk of falls and maintain independence. This study has shown that among the black middle-aged adults we interviewed, the knowledge and salience of this message is low. Public health approaches should be taken to communicate the importance of enhancing strength and balance as people approach older age, including communication and education programmes led by health professionals, who were viewed with authority amongst these participants

Three-dimensional nanomagnetism

Magnetic nanostructures are being developed for use in many aspects of our daily life, spanning areas such as data storage, sensing and biomedicine. Whereas patterned nanomagnets are traditionally two-dimensional planar structures, recent work is expanding nanomagnetism into three dimensions; a move triggered by the advance of unconventional synthesis methods and the discovery of new magnetic effects. In three-dimensional nanomagnets more complex magnetic configurations become possible, many with unprecedented properties. Here we review the creation of these structures and their implications for the emergence of new physics, the development of instrumentation and computational methods, and exploitation in numerous applications

Magnetic scanning gate microscopy of CoFeB lateral spin valve

Devices comprised of CoFeB nanostructures with perpendicular magnetic anisotropy and non-magnetic Ta channel were operated in thermal lateral spin valve (LSV) mode and studied by magnetotransport measurements and magnetic scanning gate microscopy (SGM). Due to the short spin diffusion length of Ta, the spin diffusion signal was suppressed, allowing the study of the contribution from the anomalous Nernst (ANE) and anomalous Hall effects (AHE). The magnetotransport measurements identified the switching fields of the CoFeB nanostructures and demonstrated a combination of AHE and ANE when the devices were operated in thermally-driven spin-injection mode. Modified scanning probe microscopy probes were fabricated by placing a NdFeB magnetic bead (MB) on the apex of a commercial Si probe. The dipole magnetic field distribution around the MB was characterized by using differential phase contrast technique and direct measurement of the switching field induced by the bead in the CoFeB nanodevices. Using SGM we demonstrate the influence of localized magnetic field on the CoFeB nanostructures near the non-magnetic channel. This approach provides a promising route towards the study of thermal and spin diffusion effects using local magnetic fields

Three dimensional magnetic nanowires grown by focused electron-beam induced deposition

Control of the motion of domain walls in magnetic nanowires is at the heart of various recently proposed three-dimensional (3D) memory devices. However, fabricating 3D nanostructures is extremely complicated using standard lithography techniques. Here we show that highly pure 3D magnetic nanowires with aspect-ratios of ~100 can be grown using focused electron-beam-induced-deposition. By combining micromanipulation, Kerr magnetometry and magnetic force microscopy, we determine that the magnetisation reversal of the wires occurs via the nucleation and propagation of domain walls. In addition, we demonstrate that the magnetic switching of individual 3D nanostructures can be directly probed by magneto-optical Kerr effect

Mechanism for domain wall pinning and potential landscape modification by artificially patterned traps in ferromagnetic nanowires

The interaction mechanism between transverse domain walls (TDWs) in Permalloy nanowires and artificially patterned traps is studied using high-sensitivity spatially resolved magneto-optical Kerr effect measurements and numerical simulations. T-shaped trap geometries are considered, where a DW traveling in the horizontal arm is pinned by the vertical arm. Pinning strengths as well as potential energy modifications created by the traps are measured, and the roles of the different DW characteristic parameters, such as the DW core orientation and the magnetic charge distribution within the DW, are presented. It is found that whether or not the core of the DW is aligned with the transverse arm of the T structure affects the shape of the main potential experienced by the DW, whereas the pinning strength strongly depends on which side of the V-shaped TDW interacts with the trap. The role of the magnetostatic interaction between the charge of the DW and the charge present at the junction is discussed

High efficiency domain wall gate in ferromagnetic nanowires

A transverse domain wall (DW) switchable gate with a very high efficiency is experimentally demonstrated in Permalloy nanowires using a transverse T-shaped structure. DWs are found to either travel undisturbed through the open gate or to be strongly trapped in front of the closed gate only able to travel backwards. The opening and closing of the gate depends on the magnetic configuration of the gate and is controlled using externally applied magnetic fields. Micromagnetic simulations confirm the experimental results

Asymmetric magnetic NOT gate and shift registers for high density data storage

We have developed an asymmetric ferromagnetic NOT gate and shift register optimized on a square grid. This gives rise to a two-dimensional storage scheme built up by tessellating an elementary data unit, which is scalable down to very narrow wire widths. The areal footprint of each storage unit is 15F2, where F is the minimum feature size. We experimentally demonstrate NOT operations across a chain of three gates made from Permalloy with F = 60 nm, and present a functional 15-gate, multichannel shift register with electrical injection, and optical readout