We present a combined study of the growth, structure, and related magnetic properties of Fe/W(001) using low-energy electron diffraction, scanning tunneling microscopy, the magneto-optic Kerr effect, and scanning electron microscopy with polarization analysis. Different growth regimes arise due to a competition between the stress-related elastic energy and diffusion barriers. By increasing the growth temperature, diffusion mechanisms may be switched on, activating more and more diffusion paths that lead to a reduction of the elastic energy stored in the growing films. This results in strong variations of the structure and morphology of the films. The influence of each structural and morphological phase of the Fe films on the magnetic properties can be observed and is interpreted within micromagnetic theory

International audiencePattern formation in the electrochemical deposition of iron from a thin layer of Fe(SO4) aqueous solution was investigated in a circular geometry under a magnetic field applied in the plane of growth. Arborescent aggregates were obtained whose macroscopic morphology changes from circular in zero field to rectangular in finite field, one edge of the rectangle being parallel to the field. This field-induced symmetry breaking is explained as resulting from a selection at the microscopic scale of the orientation of the branches with respect to the field, associated with a minimization of the magnetic dipolar energy of the growing branches

We investigate the dependence on the vortex structure of the propagation of fronts in stirred flows. For this, we consider a regular set of vortices whose structure is changed by varying both their boundary conditions and their aspect ratios. These configurations are investigated experimentally in autocatalytic solutions stirred by electroconvective flows and numerically from kinematic simulations based on the determination of the dominant Fourier mode of the vortex stream function in each of them. For free lateral boundary conditions, i.e., in an extended vortex lattice, it is found that both the flow structure and the front propagation negligibly depend on vortex aspect ratios. For rigid lateral boundary conditions, i.e., in a vortex chain, vortices involve a slight dependence on their aspect ratios which surprisingly yields a noticeable decrease of the enhancement of front velocity by flow advection. These different behaviors reveal a sensitivity of the mean front velocity on the flow subscales. It emphasizes the intrinsic multiscale nature of front propagation in stirred flows and the need to take into account not only the intensity of vortex flows but also their inner structure to determine front propagation at a large scale. Differences between experiments and simulations suggest the occurrence of secondary flows in vortex chains at large velocity and large aspect ratios.