Magnetic moment rare earth elements

The magnetic moments of rare earth elements are caused by the unpaired electrons in their 4f shells. These shells" are shielded by the outer shells so that chemical bonding has relatively little effect on the magnetic moments of these elements. The rare earths form a series of Laves phases of composition MB2 (M = rare earth, B = precious metal) which share the characteristic of ferromagnetic coupling at low temperatures (7). Figure 13 shows the Curie temperatures of a series of com-... 

The bond energies Qhk, Qck, and Qok proved to belong to periodic functions Qhk are observed to change parallel to the effective magnetic moment /a. In the latter, the periodic properties of rare earth elements are known to be manifested especially distinctly. For Qhk this parallelism is seen in Fig. 52 in which the values Qhk from Table XII... 

Fig. 52. The dfipondence of the bond energy Qhk, in kcal and the magnetic moment jU of rare earth elements in the Bohr magnetons, on the atomic number n (435).

M. Bode, M. Getzlaff, R. Pascal, S. Heinze, R. Wiesendanger, in Magnetism and Electronic Correlations in Local-Moment Systems Rare Earth Elements and Compounds, ed. by M. Donath, P. Dowben, W. Nolting (World Scientific, Singapore, 1998)... 

The presence of the phthalocyanine radical anion in R(Pc )(tmhd)2 (R=Y,Nd, Sm-Lu) is also supported by the magnetic, ESR and Raman spectroscopic studies (Sugimoto et al. 1983b). The magnetic moment of the diamagnetic Y and Lu is 1.65 BM which is close to the tree-spin value. Their ESR spectra, both in the solid state and in benzene solution, show a signal centered at the tree-spin value at g=2.001. The shape and g-value are characteristic of those of H(Pc ) and Li(Pc ). Complexes with paramagnetic rare-earth elements are ESR-silent, probably due to the spin-spin relaxation... 

To describe the magnetic properties of amorphous alloys containing rare earth elements with non-zero orbital moment (L 0) the Hamiltonian of eq. (25) is no longer suited. Harris et al. (1973) have proposed a model in which they assume that there is a local uniaxial field of random orientation at each of the rare earth atoms in an amorphous solid. This local uniaxial field of random orientation is closely associated with the presence of an equally random crystalline electric field. The Hamiltonian for this random anisotropy model (RAM) can be written as... 

FIGURE 7 Magnetic structures of the rare earth elements Tm, Er, Ho, Dy, Tb, and Gd. The oval shape represents a plane normal to the unique direction of the crystal. This is the plane defined by seven, atoms of a hexagonal face in Fig. 2. The arrows represent the direction of the magnetic moments with respect to this plane. [From Koehler, W. C. (1972). Magnetic structures of rare earth metais and alloys. In Magnetic Properties of Rare Earth Metals (R. J. Elliot, ed.), p. 88, Pienum Press, New York.]... 

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