Properties of Magnetic Nano-Particles

• Authors: P.A. Lindgård
• Languages of publication: EN

Abstracts

EN

The intrinsic thermodynamic magnetic properties of clusters are discussed using spin wave theory for a Heisenberg model, with a fixed magnitude of the spins S_{i}=S and site independent nearest neighbor exchange interaction. The consequences of the more realistic Hubbard model is considered in which we allow for a magnetization profile at T=0 and a structural relaxation, which in turn will give rise to a site dependent exchange interaction. It is concluded that correlation effects among the electrons play a very important role in small clusters, albeit not modifying the thermodynamic properties drastically. The finite cluster size gives foremost rise to a discrete excitation spectrum with a large energy gap to the ground state. The relaxation of the magnetization during the reversal of the external magnetic field is discussed. A first step towards a quantitative understanding of the nonequilibrium statistical mechanics in single-domain ferromagnetic particles is a systematic study of the kinetic Ising model. Results from Monte Carlo simulation and droplet theory are reviewed with particular attention to the effects of various boundary conditions, including a decrease in the number of surface bonds and an addition of surface anisotropy. A new dynamic "outside-in" flip mode is proposed.

Keywords

EN

75.30.Ds; 75.40.Gb; 76.20.+q

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 1997
• Volume: 91
• Issue: 1
• Pages: 121-133

Dates

published

1997-01

Contributors

author

P.A. Lindgård

• Department of Condensed Matter Physics, Risø National Laboratory, 4000 Roskilde, Denmark