magnetic properties

Controlling vortex circularity and polarity

Magnetic vortices are of high interest in basic and applied research, e.g. for possible applications in data storage, signal transfer, logic devices, etc. They can be described by the polarity of the central core (with the magnetization pointing "up" or "down") and their circularity (rotational direction of the magnetization around the central core). If it were possible to manipulate both properties independently, two bits could be realized by one such nano-dot with a vortex, similar to our approaches utilizing fourfold nanomagnets.

Applications of magnetic core-shell particles

Core-shell particles can be created, e.g., as hard magnetic shell and soft magnetic core or vice versa. Due to the progress in controlling the particle properties during synthesis and in characterizing the shape and magnetic properties, such bi-magnetic structures can nowadays be utilized for a variety of different applications, e.g. in magnetic recording, magneto-transport, biomedicine, or microwave absorption. Although not all properties are fully understood and controllable yet, such core-shell particles offer great potential for future applications.

Collective magnetic properties of iron oxide nanoparticle-clusters

Block copolymers can be used as “containers” which can be filled, e.g., by drugs, dyes, nanoparticles etc. Such polymeric containers can also contain ordered clusters of nanoparticles – with possibly novel collective properties, different from those of single nanoparticles and bulk material.

In a recent study, FeO_x nanoparticles of diameter 8 nm were encapsulated in such a block copolymer with ratios of polymer:nanoparticle between 20:1 and 400:1. Additionally, hybrid nanomaterials combining FeO_x with quantum dots, quantum rods, gold nanoparticles etc. were produced.

Electrodeposited magnetic nanowires

One-dimensional magnetic nano-materials – such as nanowires and nanotubes – are of special interest for the development of sensors and devices. Additionally, they can give rise to basic physical questions, regarding magnetization reversal processes in these special shapes.

Magnetic nanowires can be deposited, e.g., by electrochemical deposition. Co-Pt nanowires are of special interest for several applications due to their expected strong magneto-crystalline anisotropy. Magnetization can be probed in such nanowires using magnetic force microscopy (MFM).

Quasi-one-dimensional nanostructures

Structural, electronic and magnetic properties of different quasi-1D nanostructures – MgO nanowires, Fe3O4 nanotubes and nanowires as well as MgO/Fe3O4 core/shell nanotubes – have been examined by first-principle calculations. The effect of a deformation along the z-direction on the material properties has also been taken into account. As references, MgO and Fe3O4 bulk samples have been investigated.