SECTION 5.6. A SIMPLIFIED VIEW OF 4f-ELECTRON ANISOTROPY 57
Fig. 5.5.2 will simply orient themselves in the field gradient to yield the minimum-energy
situation.
It will be clear that for a crystal structure with a given magnitude and sign of the
minimum-energy direction for the two types of shapes shown in Fig. 5.6.1 and
will be different. This implies that the preferred moment direction for rare-earth
elements with and will also be different. It may be derived from Eq. (5.6.2)
that the energy associated with preferred moment orientation in a given crystal field
is proportional to Values of this latter quantity for several lanthanides
have been included in Table 5.6.1. A more detailed treatment of the crystal-field-induced
anisotropy will be given in Chapter 12.
References
Barbara, B., Gignoux, D., and Vettier, C. (1988) Lectures on modern magnetism, Beijing: Science Press.
Coehoorn, R. (1992) in A. H. Cottrell and D. G. Pettifor (Eds) Electron theory in alloy design, London: The
Institute of Materials, p. 234.
Hutchings, M. T. (1964) Solid state phys., 16, 227.
Kittel, C. (1968) Introduction to solid state physics, New York: John Wiley & Sons.
White, R. M. (1970) Quantum theory of magnetism, New York: McGraw-Hill.