magnetic moment of the atom - the basic physical vector quantity characterizing the magnetic properties of any substance.Source of magnetism, according to classical electromagnetic theory are microcurrents arising from the motion of the electron in its orbit.The magnetic moment - is an indispensable feature of all, without exception, elementary particles, nuclei, nuclear and electron shells of molecules.
Magnetism, which is common to all elementary particles, according to quantum mechanics, due to the presence in them of a mechanical moment called spin (own momentum quantum mechanical nature).The magnetic properties of atomic nuclei are made up of pulses of spin components of the nucleus - protons and neutrons.Electronic shell (intra-orbit) also have a magnetic moment, which is the sum of the magnetic moments of electrons are on it.
In other words, the magnetic moments of elementary particles and atomic orbitals due to intra-atomic quantum-mechanical effect known as the spin momentum.This effect is similar to the angular momentum of rotation around its central axis.Spin momentum is measured in Planck's constant - the fundamental constants of the quantum theory.
All neutrons, electrons and protons, of which, in fact, is the atom, according to Planck, have a spin of ½.In the structure of the atom, electrons revolving around the nucleus in addition to the spin momentum are also the orbital angular momentum.The core, though, and takes a static position, also has angular momentum, which creates the effect of the nuclear spin.
magnetic field, which generates an atomic magnetic moment is determined by various forms of angular momentum.The most significant contribution to the creation of a magnetic field makes it a spin effect.According to the Pauli exclusion principle, according to which two identical electrons can not stay at the same time in the same quantum state, bound electrons merge with their spin impulses become diametrically opposite view.In this case, the magnetic moment of the electron is reduced, which reduces the magnetic properties of the entire structure.In some cells having an even number of electrons, this point is reduced to zero, and the substance no longer have magnetic properties.Thus, the magnetic moment of individual elementary particles has a direct influence on the magnetic quality of all nuclear atomic system.
ferromagnetic elements with an odd number of electrons will always have a non-zero magnetism due to the unpaired electron.In such elements adjacent orbital overlap and all unpaired electron spin moments take the same orientation in space, which leads to the achievement of the lowest energy state.This process is called exchange interaction.
With this alignment of the magnetic moments of ferromagnetic atoms of a magnetic field.A paramagnetic elements composed of atoms with magnetic moments disoriented, have no intrinsic magnetic field.But if they affect the external source of magnetism, the magnetic moments of the atoms align, and these elements also acquire magnetic properties.