By considering a Hamiltonian that includes the crystalline electric field and exchange interaction components we showed theoretically that paramagnetic ${\mathrm{PrNi}}_5$ exhibits an anomalous entropy behavior in which the magnetic entropy increases with increasing magnetic field at low temperature. This anomaly in magnetic entropy can be fully understood and is associated with the crossing of the two lowest magnetic energy levels $({\Gamma }_4$ and ${\Gamma }_1).\mathrm{}$ Experimental verification of the anomalous behavior of the magnetic entropy in polycrystalline ${\mathrm{PrNi}}_5$ was obtained.

• Received 16 June 1998

DOI:https://doi.org/10.1103/PhysRevB.58.14436