Program Highlights

Sculptured Cobalt Nanomagnets

E. Schubert, A. C. Kjerstad, D. Schmidt, M. Schubert,
S.-H. Liou, and R. Skomski
Nebraska MRSEC

Nanomagnets establish a promising field of research with a broad variety of applications in magnetic memory, bioengineering or medical diagnosis and treatment. However, exploitation requires understanding, control and manipulation of magnetic properties, which are mainly influenced by the nanomagnet’s size and shape as well as by interactions between ensembles of nanomagnets arranged in large scale arrays. We fabricate chiral and non-chiral three-dimensional thin-film nanomagnets by means of oblique particle flux deposition. The material exhibits unique magnetic properties associated with the shape of the structures and with magnetic interactions between adjacent features. An example is the preferential magnetization direction (easy axis) in non-chiral cobalt films from slanted nanoneedles. Measurements reveal that the easy axis is rotated towards the film rather than being parallel to the needle direction, as expected from the needles’ shape anisotropy. Model calculations suggest that magnetostatic interactions between the needles are responsible for the observed behavior. The calculations predict that the easy axis depends on both the tilting angle and the packing fraction of the nanoneedles. Accordingly, the easy axis varies from parallel to the needles for low packing fractions to almost in the film plane for close-packed needle films, which was indeed detected in our experiments.

This research is supported by the National Science Foundation, Division of Materials Research, Materials Research Sciences and Engineering Program, Grant 0820521.

Sculptured Thin Films from Cobalt a) non-chiral (inclined needles), b) chiral (spirals).