J. Arabski

Engineering magnetic responses in hcp cobalt thin films

Abstract We have analyzed the local and global magnetic properties of high quality grown (0001) hcp cobalt films of thicknesses varying from 50 to 500 nm. Local domain imaging by magnetic force microscopy together with magnetization measurements confirm the periodic multidomain structure with perpendicular orientation predicted by Kittel for such thicknesses and allow a full characterization of the film. The perpendicular and parallel saturation fields have been successfully modeled and fitted. The magnetic domain width of between a few tens of nanometers to a few hundreds of nanometers is described using a √ h law, where h is the film thickness. Well characterized cobalt films appear to be good candidates for further investigations.

Correlation between the structural and transport properties of granular CoAg systems prepared by MBE

Abstract We have studied the structural and magnetotransport properties of epitaxial, Co/Ag granular alloy films prepared by molecular beam epitaxy at different growth temperatures. The rapid decrease in the magnetoresistance above 35% concentration at low temperature deposition is related to the presence of Co paramagnetic impurities within the Ag matrix, which has the effect of reducing the spin diffusion length by increased spin-flip scattering and indicates that the spin diffusion length in such granular systems is a determining length scale at the origin of the magnetoresistance.

Influence of magnetic anisotropy and its distribution on the hysteresis loops upon patterning thin films

We compare the hysteresis loops of ferromagnetic films and dots down to 0.2 μm. Samples are made of Co–Pt multilayers with different Co thicknesses so as to vary the perpendicular magnetic anisotropy. We determined the first- and second-order anisotropies of the films, as well as the first-order anisotropy distribution, and show that from these quantities the switching field distribution of dots can be predicted. We also explain through a simple criterion—the relation between the anisotropy distribution and the minimum nucleation field—why in some cases the hysteresis loops recorded along the easy axis on the films undergo a dramatic change after patterning.

Structural and magnetic study of submicronic single crystal cobalt box arrays

We present a study of magnetic dot arrays fabricated in Ru(5 nm)/Co/Ru(32 nm) films with cobalt thickness varying from 10 to 500 nm. Large array areas up to 5×5 mm2 have been obtained with lateral dot size and spacing of 0.5 μm. The magnetization curves are characteristic of a perpendicular magnetized multidomain structure. Lateral size reduction does not drasti‐ cally change the domain structure but has immediate consequences on the nucleation and saturation fields. A magnetic force microscopy study confirms the perpendicular multidomain struc‐ ture and provides intrinsic magnetic characteristics.