Zeeman effect on magnetic susceptibility in singlet ground state PrNi5

The Zeeman effect on the crystal electric field (CEF) magnetic susceptibility in 4f-electron singlet ground state (SGS) systems is studied analytically in the framework of the molecular-field model and experimentally by measuring the magnetic susceptibility of SGS compound PrNi₅. The most striking result of the analysis is the shift of the zero-field magnetic susceptibility maximum to lower temperatures in magnetic field. This thoroughly CEF effect is a direct consequence of the convergence of the SGS and the low lying Zeeman branch of the first excited state in an applied magnetic field. The observed shift of the susceptibility maximum from 14 K to 9 K in polycrystalline PrNi₅ by applying a magnetic field of 9T confirms the foregone conclusion.