Simulations of magnetic microstructure in thin film elements used for programmable motion of magnetic particles

The results of two-dimensional micromagnetic modeling of magnetization patterns in Permalloy ellipses under the influence of rotating constant-amplitude magnetic fields are discussed. Ellipses of two different lateral sizes have been studied, 0.5m x 1.5m and 1m x 3m. The amplitude of the rotating magnetic field was varied between simulations with the condition that it must be large enough to saturate or nearly saturate the ellipse with the field applied along the long axis of the ellipse. For the smaller ellipse size it is found that the magnetization pattern forms an S state and the direction of the net magnetization lags behind the direction of the applied field. At a critical angle of the rotating magnetic field the direction of the magnetization switches by a large angle to a new S state. Both the critical angle and the angle interval of the switch depend on field amplitude. For this new state, it is instead the applied field direction that lags behind the magnetization direction. The transient magnetization patterns correspond to multi-domain patterns including two vortices, but this state never exists for the equilibrated magnetization patterns. The behavior of the larger ellipse in rotating field is different. With the field applied along the long-axis of the ellipse, the magnetization of the ellipse is nearly saturated with a vortex close to each apex of the ellipse. As the field is rotated, this magnetization pattern remains and the net-magnetization direction lags behind the direction of the field until for a certain angle of the applied field an equilibrium multi-domain state is created. Comparisons are made with corresponding experimental results obtained by performing in-field magnetic force microscopy on Permalloy ellipses.

(Pro)Motion Pictures: Len Lye in the Thirties

This article examines Len Lye’s film-making in the 1930s within a broader visual arts context, seeking to clarify the nature and extent of his involvement in British documentary film culture at this time. In particular, it demonstrates how Lye's method of fusing 'live action', found footage, and animation techniques created the possibility of a radical documentary practice that could reconcile promotional advertising and commercial art with avant-garde abstraction and kinaesthetic experimentation. In particular, the article focusses on Lye's N. or N.W. (1937, 35mm, b&w, 10 mns), arguing that his work from this period should be regarded as central - and not marginal - to any serious reassessment of Britain's “Documentary Movement” of the inter-war era, and its relations to any history of the cinema and visual culture.

British Film in the 1970s: Capital, Culture and Creativity

Throughout the 1970s the British film industry struggled to produce films which performed well at the box office and appealed to audiences. As a result the decade has often been considered as one of the low points of British cinema. But was this really the case? Conventional film histories of the decade have emphasised key texts and specific genres, such as the Bond films, the Carry On series or low budget horror. Yet British cinema in this period offered a great deal more to audiences and careful study of original documents demonstrates the diversity and variety of an industry, and a decade, typically perceived as limited and unimaginative. An examination of important material – much of it newly discovered or previously underused – offers an insight into the industry in this decade while key case studies present a detailed picture of the eclectic, diverse and often challenging film culture of the period.

Programmable motion and separation of single magnetic particles on patterned magnetic surfaces

Motion of single micrometer-sized magnetic particles on patterned magnetic surfaces is controlled by a rotating magnetic field (see Figure and cover). Patterns of thin-film magnetic elements are tailored to form transport lines. Individual particles are separated by adding junctions to the transport lines. The method can improve existing applications in biotechnology and generate new ones in life sciences.

INTERPLAY OF CAF2 SUBSTRATE ROUGHENING AND FILM DEPOSITION RATE ON RADIATIVE SCATTERING OF SURFACE-PLASMON POLARITONS FROM AG FILMS

The radiative decay of surface plasmon polaritons has been investigated in an attempt to characterize the surface roughness of Ag films prepared under different conditions. The polaritons were excited by the method of attenuated total reflection of light. The films were deposited on the face of a 60-degrees BK-7 glass prism at a rate that was deliberately fixed in two different ranges (centred on 0.1 and 10 nm s-1) and in some cases a CaF2 underlayer was used to roughen the film surfaces. The intensity of the scattered light emitted from the opposite face of the films was measured as a function of direction for each using the same sensitivity scale and was correlated with the preparation of the film. It was found that on nominally smooth substrates fast-deposited thinner films give out more light and are deduced to have greater short wavelength (300-600 nm) roughness amplitude. There is also evidence for long wavelenth (7 mum) periodic roughness due to the prism substrate itself. On CaF2 roughened surfaces the light output from the films is further increased and the peak intensity is backward directed with respect to the exciting laser beam direction. Here roughness on a lateral scale of 350 nm is responsible. Also, elastic scattering of surface plasmon polaritons at grain boundaries reduces the light output from fast deposited, small grain, films on CaF2 roughened surfaces. Overall, a consistent picture of roughness induced radiative polariton decay emerges for all cases studied.