Magnetically assisted processing of a medium.

The invention relates to a processing device(100) and a method for processing a medium in a processing chamber(121). The processing comprises the addition of magnetic particles(M) to the medium and the mixing of the medium by manipulating said magnetic particles with a time-variable magnetic field(B), particularly a partially oscillating or rotating field. The magnetic field(B) may be generated with a multipole magnetic field generator(110) comprising four subunits(111A,111B), each having a core(113A,113B) with a surrounding coil(112A,112B) and with a top surface(114A,114B), wherein all top surfaces of said subunits are preferably arranged in the same plane and wherein all cores are substantially parallel to each other

Ion sculpting of Cu(001)

In this thesis a comprehensive investigation of low - energy ion\ud bombardment of the (001) surface of copper is presented. The experimental investigations focus on the surface morphology emerging as a result of ion bombardment. It is quantied by average distances and\ud the formation and orientation of facets

Magnetically controlled rotation and torque of uniaxial microactuators for lab-on-a-chip applications

We demonstrate the controlled rotation and torque generated by uniaxial magnetic microactuators formed by two bound superparamagnetic particles in a fluid. The torque and rotation are precisely controlled by rotating magnetic fields, generated by an external electromagnet or by on-chip current wires. We present the magnetic energy equations and the equations of motion for two-particle microactuators, with contributions from the permanent and induced magnetic moments of the particles. A comparison of theory and experiments allows an estimation of the different moments with accuracy better than 10% across a wide frequency range. At low frequencies and low magnitudes of the applied magnetic field, both the permanent and induced moments of the particles have contributions to the torque. At either high fields or high frequencies, the torque is dominated by the induced moment. The predictability of the torque is highest in the regime of low frequencies and high field, where the torque has a large magnitude and is determined by the magnetic shape anisotropy of the microactuator. A comparison of rotation in bulk fluid and on a chip surface shows an increase of friction by a factor 9 originating from the surface proximity. The detailed understanding of the torque and rotation of two-particle uniaxial magnetic microactuators opens a range of possibilities in lab-on-a-chip applications, such as the actuation of single molecules, fluid mixing in microfluidic chambers, and novel cluster-based assays

Antisite Defects Stabilized by Antiphase Boundaries in YFeO 3 Thin Films

YFeO$_3$ thin films are a recent addition to the family of multiferroic orthoferrites where Y\textsubscript{Fe} antisite defects and strain have been shown to introduce polar displacements while retaining magnetic properties. Complete control of the multiferroic properties, however, necessitates knowledge of the defects present and their potential role in modifying behavior. Here, we report the structure and chemistry of antiphase boundaries in multiferroic YFeO$_3$ thin films using aberration corrected scanning transmission electron microscopy combined with atomic resolution energy dispersive X-ray spectroscopy. We find that Fe\textsubscript{Y} antisites, which are not stable in the film bulk, periodically arrange along antiphase boundaries due to changes in the local environment. Using density functional theory, we show that the antiphase boundaries are polar and bi-stable, where the presence of Fe\textsubscript{Y} antisites significantly decreases the switching barrier. These results highlight how planar defects, such as antiphase boundaries, can stabilize point defects that would otherwise not be expected to form within the structure