Crystalline electric field effects in the magnetic properties of hexagonal praseodymium compounds

The high field magnetization and the magnetic susceptibility of hexagonal praseodymium compounds are calculated on the basis of a molecular field Hamiltonian, including the CEF potential, a Zeeman term, and isotropic exchange interactions. At low temperatures it is shown that the full magnetic moment of the Pr³⁺ ion is always reached in a stepwise manner for a magnetic field applied along the c-axis. Perpendicular to the c-axis this occurs only in the case of a Γ₄ ground state. This is a pure CEF effect, resulting from the crossing of the ground state by an excited state with a higher magnetic moment. The temperature dependence of the magnetic susceptibility would have a maximum corresponding to an appreciable population of an excited state with a greater magnetic moment. Some hexagonal Pr compounds are considered in which the discussed effects are or should be observable.