Hybrid magnetic materials - microscopic origins with macroscopic effects

Intrinsic magnetic properties like the magnetic anisotropy, the interface and interlayer ex-change coupling depend to a large degree on the microscopic structure of the investigated layer systems. In the case of amorphous alloys short range order phenomena are important. For exchange coupled layer systems the interfacial roughness plays a crucial role for the determination of the integral material properties. However, a local modification of the magne-tization direction and thus the appearance of magnetic domains are only possible on a length scale larger than the magnetic correlation length of the corresponding material, which is typically in the range between 10 - 1000 nm. By means of ion irradiation techniques the structural origins of the magnetic parameters can be modified on a length scale similar to or even below the exchange correlation length. Since a local variation of the magnetization direction is only possible to some extent the layer system acts as an effective medium with macroscopic modified properties - so-called hybrid materials. 

In this research area the transition from purely magnetically patterned layers to magnetic hybrid materials will be investigated systematically. The domains and domain wall structures on one hand and the effective magnetic anisotropy field and coercive field on the other hand depend here dramatically on the patterning sizes and geometries. The center of the research therefore is focused on the investigation of the functional relation between the microscopic modi-fi-ca-tions, the macroscopic modified parameters in correlation with these patterns. The scalability of the results will be investigated by comparison of different material systems which exhibit different exchange correlation length.

 

Pure magnetic patterning due to energy dissipation (ion irradiation)

In the following a few examples are shown where the energy dissipation of the ions leads to a local modification of the interface morphology or the short range order and thus to a variation of the observed magnetic parameters:

Pure magnetic patterning due to doping of the magnetic films by ion implantation

In contrast to the magnetic patterning by means of energy dissipation here the ions are implanted in a thin film in order to change the composition and thereby modify its magnetic properties.

  • Saturation magnetization
  • Curie temperature 
  • Coercive field
  • Magnetic damping

Publications:

1. Tailoring Magnetism by Light Ion Irradiation
J. Fassbender, D. Ravelosona, Y. Samson
J. Phys. D: Applied Physics 37, R179 (2004).

2. Magnetic anisotropy and domain patterning of amorphous films by He-ion irradiation
J. McCord, T. Gemming, L. Schultz, J. Fassbender, M. O. Liedke, M. Frommberger, E. Quandt
Appl. Phys. Lett., 86, 162502 (2005).

3. Domain structure of magnetically micro-patterned PtMn/NiFe exchange biased bilayers
K. Potzger, L. Bischoff, M. O. Liedke, B. Hillebrands, M. Rickart, P. P. Freitas, J. McCord, J. Fassbender
IEEE Trans. Magn., 41, 3610 (2005).

4. Magnetic domains and magnetization reversal of ion-induced magnetically patterned RKKY-coupled Ni81Fe19/Ru/Co90Fe10 films
J. Fassbender, L. Bischoff, R. Mattheis, P. Fischer
J. Appl. Phys. in press (2005).

Poster contributions:

1. Magnetic domain structure of magnetically micro-patterned PtMn/NiFe exchange bi-ased bilayers
K. Potzger, L. Bischoff, M. O. Liedke, B. Hillebrands, M. Rickart, P. P. Freitas, J. McCord, J. Fassbender
International Magnetics Conference, Intermag 2005, Nagoya, Japan.

2. Magnetic properties and domain formation in amorphous films anisotropy patterned by ion irradiation
J. McCord, J. Fassbender, M. Frommberger, M. O. Liedke, R. Schäfer, E. Quandt
International Magnetics Conference, Intermag 2005, Nagoya, Japan.

3. Tailoring magnetic properties of permalloy by means of Cr implantation
J. Fassbender, J. McCord, R. Mattheis, K. Potzger, A. Mücklich, J. von Borany
Heraeus Seminar "Ions at Surfaces: Patterns and Processes", Bad Honnef, Germany, 2005.