Single Domain Nanomagnet: A Gaint spin
A single domain nanomagnet comprises ~10^4 spins directed along the same direction due to the exchange interaction between them. When the spins rotate due to various external effects, they move altogether as a unison as if they were a giant single spin. This giant spin can lie in the plane where shape of the structure (e.g. elliptical, rectangular, circular and so on) determines the direction along which it points to. Otherwise, it can point perpendicular to the plane in which case geometry of the structure does not matter. The former is called in-plane anisotropy and the latter is named as perpendicular anisotropy.
