Eigenstates and Phase Transitions of Ising Spin Network Immersed in the Incommensurate Exchange Field

抄録

A simple incommensurate mean field model is introduced to explain complex magnetic phase diagrams of various rare-earth intermetallic compounds such as CeSb and CeBi. The eigenstates and their energies of the Ising spin chain immersed in the exchange field with magnitude J, wave vector k and phase δ are determined. The spin S(r) is assumed to point in the local field direction. The eigenstates are classified into three groups, the irrational states, rational states {k} with δ=0 and rational states {k} with δ=π⁄2n where n is the state index given by a positive integer. The phase diagram of CeSb is sketched by the model. It is emphasized that the present model suggests an effect of the spin coupling to the formation of conduction band electrons and the effect on the heavy fermion and superconductivity is discussed.