抄録
The s-f exchange interaction is derived from the Anderson Hamiltonian for the (4f)^2 configuration in the lowest J-multiplet 3{H}4. The angular momentum conservation holds including both spin and orbital motion. For the case when the crystal field lifts the (2J+1)-fold degeneracy to yield a singlet ground state, we derive an effective hyperfine coupling between a nuclear spin and a conduction electron by eliminating the 4f-electrons. From it the RKKY interaction between the nuclear spins is obtained, which is of the form I_i , {\hat{J}}i j , I_j, where {\hat{J}}i j is a symmetric tensor whose elements depend on the angles of Ri j relative to the crystal axes in addition to the distance {R}i j. To determine the nuclear ordering in the mean field approximation, the eigen-value problem is investigated for the Fourier transform of {\hat{J}}i j. Tensorial nature of {\hat{J}}i j brings much more complicated features into the enhanced nuclear magnetism of Pr than that expected from the conventional scalar type RKKY interaction, such as the occurence of two successive phase transitions between the paramagnetic state and T=0 state.
