Magnetic anisotropy Ferromagnetism

although exchange interaction keeps spins aligned, not align them in particular direction. without magnetic anisotropy, spins in magnet randomly change direction in response thermal fluctuations , magnet superparamagnetic. there several kinds of magnetic anisotropy, common of magnetocrystalline anisotropy. dependence of energy on direction of magnetization relative crystallographic lattice. common source of anisotropy, inverse magnetostriction, induced internal strains. single-domain magnets can have shape anisotropy due magnetostatic effects of particle shape. temperature of magnet increases, anisotropy tends decrease, , there blocking temperature @ transition superparamagnetism occurs.