Magnetic Nanoparticles as Many-Spin Systems

2005

We have demonstrated by different analytical and numerical methods the importance of accounting for the magnetization inhomogeneities in magnetic nanoparticles, especially in the presence of surface anisotropy. The latter makes the magnetization inhomogeneous even at T = 0 and in general modifies the relation between the intrinsic and induced magnetizations. It also changes the magnetization switching mechanism, since for strong surface anisotropy the particle’s spins switch cluster-wise. For weak surface anisotropy we have been able to calculate the spin canting in the particle analytically and to obtain a novel second-order contribution to the particle’s overall anisotropy. It remains to …