6b geff 12b fig 716 calculated density of states of ni

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Unformatted text preview: many ionic compounds of d- and f- transition metals Does not apply for 3d-transition metal ferromagnets Ni, Co, Fe. 7-31 Band ferromagnetism of Ni, Co and Fe 3d-transition metals Experiment: J = 1/2 ⇒ magnetization due to electron spins Ms(0) = (1/2)gµBnatoms ⇒ g = 1.2 ≠ 2 ! for Ni Theoretical explanation analogous to Pauli paramagnetism: 10 electrons in overlapping 3d- and 4s-bands effective moment per atom: µeff = 0.6µB ⇒ gµeff = 1.2µB Fig. 7.16 Calculated density of states of Ni. Due to the quantummechanical exchange interaction there is a preferred orientation of the spins, which gives rise to an external exchange field. Orientation of the spins parallel to the exchange field to an energy reduction while antiparallel orientation shifts the density of states to higher values. This lends to a net number of 0.6 electrons per atom with spin orientation parallel to the exchange field at 0K and hence an effective magnetic moment of 0.6µB per atom. This so-called band ferromagnetism is analogous to the Pauli par...
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