The electric charge manifests as electric field in the space surrounding this particle, the magnetic moment manifests as magnetic field, and the manifestation of spin can be seen as the hypothetical spin-field . The spins of electrons and protons are considered to be connected with their moments of quantity of motion. But since this conception contradicts the prohibition for overlight velocities, spin is therefore considered to be just a quantum-mechanical value. So, we know that there exists the physical value called spin . If in any substance the spins of particles have a preferable direction, then this is interpreted as spin polarization of substance.
Every substance creates the spin-field in the space surrounding it when polarized by spins.
The simplest way to achieve the selective spin orientation is through the mechanical rotation of objects. Thus, the spins will be oriented along the axis of rotation. Barnet applied this method in his experiments when he observed the magnetization of a ferrite rod as the result of the rod rotation. Since the spin is connected with the magnetic moment, the spin-field produced as a result of selective spin orientation manifested itself as magnetization of ferrite rod. But the effective creation of the spin-field using this method has several problems.