Surface-induced anisotropy and multiple states in elongated magnetic nanoparticles

摘要

For ellipsoidal magnetic nanoparticles the values of surface-induced uniaxial anisotropy have been derived from an analytical model as functions of aspect ratios and particle sizes. The authors show that this specific anisotropy can stabilize multiple magnetic states in the system, suppress demagnetization effects, and prevent superparamagnetism. The calculated phase diagrams indicate the stability regions of different phases and the transition fields between them. By tuning sizes, geometry, and surface anisotropy of elongated particles a well-defined sequence of magnetic switching transitions can be realized in prescribed magnetic fields. This can be used in magnetic recording and spin electronic technologies.