Figure 7. Chain-like assemblies.

Computed hysteresis loops for arrays of nanoparticles of different length (values of N indicated), and the limit case of a single particle, where H_A = 2 K/M_S is the anisotropy field of the particles. The temperature was introduced in terms of the anisotropy energy barrier of the particles, t = k_BT/2KV = 0.001. The inset shows the magnetic response on increasing the temperature for the N = 1 and 10 cases, illustrating the higher thermal stability of the chains. The schematic picture shows particles within a chain possessing easy axes contained within an angle of π/4 (cubes are only for illustration purposes, since spherical nanoparticles could also form chains).