Magnetic Anisotropy Of Fine Particles :: essays research papers

"Magnetic Anisotropy Of Fine Particles" In nature, single domain particles are magnetized to saturation, where the magnetization has an easy bloc, or several easy axes, along which it prefers to lie. In this case the total home(a) energy is minimum. Rotation of the magnetization vector away from the easy axis vertebra is possible only by applying an external magnetic country. This phenomenon is weeped magnetic anisotropy. Thus, the verge magnetic anisotropy describe the dependence of the internal energy on the focussing of magnetization of the particle. The energy term of this kind is called a magnetic anisotropy energy. in general it has the same symmetry as the crystal structure of the particle material, and we call it a magnetocrystalline anisotropy or crystal anisotropy . This kind of anisotropy is due mainly to spin-orbit pairing . For instance, we consider an anisotropy that is uniaxial in symmetry. In this case, one of the simplest expressions of the magnetic anisotropy energy is Ea=KaVsin2 , where is the tap between the magnetization vector and the symmetry axis of the particle, V is the slew of the particle, and Ka is the anisotropy energy per unit volume or the anisotropy constant. The srength of the anisotropy in any finicky crystal is measured by the magnitude of the anisotropy constants.Consider a exemplification of fine particles having no preferred orientation of its particles. If we have spherical particles, at that place will be no shape anisotropy, and the same applied field will magnetize it to the same extent in any direction. solely if it is a nonspherical particles, the magnetization vector will not necessarily lie along an easy crystallographic axis, but rather along an axis whose demagnetizating field is a minimum. This is called shape anisotropy and was proposed by (1947).In real administrations, thither is always a particle size and shape distributions as come up as a distribution of particle enviroments, depe nding on the topology of the system (e.