Some crystalline field effects in metals

We discuss different physical effects which are caused by the crystalline electric field splitting of rare earth ions in metals. Thus, the rare earth ions may be impurities dissolved in a metallic matrix or they may form a regular lattice. In the former case we distinguish between the cases of a normal conducting and a superconducting matrix. The influence of the crystalline field splitting on the properties of the conduction electrons is calculated. In the case of a normal matrix anomalous behaviour of the thermoelectric power is found due to the impurity levels. If the matrix is superconducting large deviations result from the theory of Abrikosov and Gorkov which describes the influence of non-split magnetic impurities on superconductivity. A comparison of the theory with available experiments is presented.

For the case that the rare earth ions form a regular lattice we discuss various aspects of the collective excitations in the paramagnetic state. Special attention is paid to the soft mode problem of exchange induced ferromagnets. Furthermore we discuss the influence of impurities on the excitation spectrum (localized modes, resonant modes etc.) and on the magnetic ordering temperature.