Crystal-field calculation of Pr3+ in orthorhombic PrNi2Al5 from 27Al NMR Knight shift

The crystalline-electric-field (CEF) parameters for the Pr 3+ ion in nonmagnetic PrNi 2 Al 5 has been estimated using the 27 Al nuclear magnetic resonance (NMR) Knight shift, K, measured in a grain-aligned sample in the temperature range 3.5-310 K. The behaviour of the shift is well explained by van Vleck paramagnetism. The overall crystal-field splitting (A), obtained from the temperature dependence of K, is at least 100 K more than the value reported from magnetic susceptibility measurements. Moreover, the first two low lying excited states are 44 and 96 K above the ground level.