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Unformatted text preview: amagnetism if one envisions the exchange field as an extreemly strong magnetic field. The strong magnetization is also caused by the high density of stated of the Fermi level in the d-band.
7-32 Domain structure
Ferromagnetic sample generally has no net magnetic moment! Reason: domain structure ⇒ reduction of magnetic energy. Fig. 7.18 Illustration of the reduction of magnetic energy by formation of domains of uniform spin orientation. The domains are generated by so-called Bloch walls, where the spin orientation changes gradually within a distance of the order of 40nm (for Fe). Typical domain sites are 1 - 10 µm. The microstructure of the domain results from a competition between reduction in magnetic energy and the energy required to form Bloch walls, which originates from the rotation of the spins away from the direction of easiest magnetization. Magnetic anisotropy: prefered direction of magnetization,e.g., <100> in Fe. Reason: orbits of electrons of lattice atoms are affected by electrostatic field of neighbouring atoms ⇒ anisotropy. Anysotropy in orbital moments affects spin orientation via spin-orbit coupling. * * The orbital moment of an electron around the central nucleus gives rise to an orbital magnetic moment. The corr...
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- Spring '02