|AVS 57th International Symposium & Exhibition|
|Thin Film||Wednesday Sessions|
|Session:||ALD: Nanostructure, Magnetics and Biological Applications|
|Presenter:||J. Bachmann, University of Hamburg, Germany|
|Authors:||J. Bachmann, University of Hamburg, Germany
K. Nielsch, University of Hamburg, Germany
|Correspondent:||Click to Email|
Atomic layer deposition (ALD) is uniquely suited to the conformal deposition of magnetic thin films in pore structures of high aspect ratio, while offering precise tuning of the layer thickness and high uniformity. Combining one or several layers of ALD with self-ordered porous anodic alumina membranes used as templates yields arrays of magnetic nanotubes with diameters tunable between 20 and 200 nm, wall thicknesses from 2 to 40 nm, and lengths set anywhere between 0.1 and 100 microns. The magnetic properties of such nanotubes strongly depend on their geometry, as evidenced on the ensemble and single-object levels by SQUID and MOKE magnetometries, respectively. The structural parameters can be chosen so as to favor a certain mechanism of magnetization reversal or another.
Further structural complexity can be created by introducing additional preparative steps. Interference lithography can be exploited for sculpting tubes with controlled modulations in diameter. Electrodeposition enables us to synthesize wires in which a core and a shell of two distinct magnetic materials are separated by a non-magnetic spacer layer. In those cases, the geometric parameters are still accurately controlled and tunable. The particular geometric characteristics of the system directly transpire into their magnetic properties: diameter modulations may hinder the propagation of magnetic domain boundaries, whereas core-shell structures may give rise to two distinct magnetic reversal events.