In this work, we investigate the use of post-fabrication thermal nanoconversion (TNC), using a heated scanning probe tip, to modify the magnetic properties of Ni80Fe20 elliptical nanoislands with varying aspect ratio. Despite Ni80Fe20 being unoptimized for TNC, by comparing quasistatic and dynamic magneto-optical Kerr effect microscopy measurements, we demonstrate that TNC at a contact temperature of 250 °C increases the saturation magnetization of the treated nanoislands, reaching a value close to 800 kA/m. Micromagnetic simulations of the nanoislands indicate that the TNC technique can be used to alter the remanent state, from a single domain to a vortex. These results demonstrate the opportunities afforded by TNC to modify the properties of selected areas in a thin film or a patterned sample, particularly when designing magnonic crystals and other nanomagnetic devices.
The non-local spin valve (NLSV) is a useful device for studying spin transport at nanoscopic dimensions, with potential technological applications. Despite this appeal, background signals, unrelated to spin diffusion, often hinder the interpretation of spin signals in NLSVs and could compromise performance in future devices. In this paper, we comprehensively investigate these background signals in all-metallic NLSVs fabricated from a variety of ferromagnetic (FM; Ni80Fe20, Fe, Co) and nonmagnetic (NM; Al, Cu) metals. We demonstrate that a background signal emerges in AC measurements, with contributions from both current spreading and thermoelectric effects, with a complex dependence on both temperature and FM injector-detector separation. Despite the complexity of these dependencies, we demonstrate excellent agreement with three-dimensional finite-element modelling that accounts for current-spreading and thermoelectric effects, across a wide range of temperatures, FM separations, and FM/NM pairings. This approach additionally offers a means to estimate the Seebeck coefficients for the tested FM/NM pairings, providing further insight into the charge and heat flow in such nanoscopic spintronic devices.
Abstract We report on the electronic and magnetic properties of superconductor-ferromagnet heterostructures fabricated by electron beam evaporation on to unheated thermally oxidised Si substrates. Polycrystalline Nb thin films (5 to 50 nm thick) were shown to possess reliably high superconducting critical temperatures ( $$T_{c}$$ T c ), which correlate well with the residual resistivity ratio (RRR) of the film. These properties improved during ex-situ annealing, resulting in $${\Delta }T_{c}$$ Δ T c and $${\Delta }$$ Δ RRR increases of up 2.2 K ( $$\sim$$ ∼ 40% of the pre-annealed $$T_{c}$$ T c ) and 0.8 ( $$\sim$$ ∼ 60% of the pre-annealed RRR) respectively. Nb/Pt/Co/Pt heterostructures showed substantial perpendicular anisotropy in the ultrathin limit (≤ 2.5 nm), even in the extreme limit of Pt(0.8 nm)/Co(1 nm)/Pt(0.6 nm). These results point to the use of electron beam evaporation as route to line-of-sight deposited, low-thickness, high quality Nb-based superspintronic multilayers.
The nonlocal spin valve (NLSV) enables unambiguous study of spin transport, owing to its ability to isolate pure spin currents. A key principle of NLSV operation is that the "spin signal" is invariant under application of in-plane magnetic fields (above the ferromagnetic contact saturation field). Yet, for certain ferromagnet/normal metal pairings in NLSVs, an unexpected field enhancement of the spin signal occurs, presenting a challenge that has, thus far, been difficult to resolve with existing models. By correlating the extracted spin transport parameters with material, temperature, and field dependencies, in this work we identify field quenching of magnetic impurity scattering as the origin of this effect, confirmed by excellent agreement between our results and field-dependent Kondo theory. In addition to addressing this long-standing mystery, our findings highlight a potential systematic underestimation of spin transport parameters. By identifying signature field and temperature dependencies, we provide here a relatively simple means to isolate and quantify this additional relaxation mechanism.
We discuss a series of activities for A-level students which can be carried out using the binding blocks three dimensional chart of nuclides. The planned activities cover four main sections which can be linked to the A-level curriculum; nuclear decays (as seen through the different colours on the chart), medical physics (medical isotopes highlighted on the chart), fusion on Earth (binding energy demonstrated through tower heights) and stellar fusion (which has a limit at 56Fe, illustrated by the decreasing tower heights).
We discuss a series of activities for A level students which can be carried out using the Binding Blocks three dimensional chart of nuclides.The planned activities cover four main sections which can be linked to the A level curriculum; nuclear decays (as seen through the different colours on the chart), medical physics (medical isotopes highlighted on the chart), fusion on Earth (binding energy demonstrated through tower heights) and stellar fusion (which has a limit at 56 Fe, illustrated by the decreasing tower heights).
It is known that perceptual organization modulates the salience of visual symmetry. Reflectional symmetry is more quickly detected when it is a property of a single object than when it is formed by a gap between two objects. Translational symmetry shows the reverse effect, being more quickly detected when it is a gap between objects. We investigated the neural correlates of this interaction. Electroencephalographic data was recorded from 40 participants who were presented with reflected and translated contours in one- or two-object displays. Half of the participants discriminated regularity, half distinguished number of objects. An event-related potential known as the Sustained Posterior Negativity (SPN) distinguished between reflection and translation. A similar ERP distinguished between one and two object presentations, but these waves summed with the SPN, rather than altering it. All stimuli produced desynchronization of 8-13 Hz alpha oscillations over the bilateral parietal cortex. In the Discriminate Regularity group, this effect was right lateralized. The SPN and alpha desynchronization index different stages of visual symmetry discrimination. However, neither component displayed the Regularity × Objecthood interaction that is observed in speeded discrimination tasks, suggesting that integration of visual regularity with objectness is not inevitable. Instead, both attributes may be processed in parallel and independently.