Magnetism of ErNi2B2C investigated with a two-ion model for rare-earth antiferromagnets

A two-ion model for rare-earth antiferromagnets was employed in the present work to study the magnetic and thermodynamic properties of ErNi2B2C, and derive an analytic formula for the Néel temperature of the compound with the quantum perturbation theory. To apply the theory, four new base functions had to be composed due to the special forms of its crystal-field (CF) wavefunctions. Our theoretical analysis suggested that the magnetic behavior of the compound be governed by these low-lying CF levels in the temperature region at least up to 100 K.

► We used the two-ion model to investigate the magnetic properties of ErNi2B2C. ► We succeeded in reproducing the magnetic specific heat of the compound. ► We derived a formula for the Néel temperature of the crystal with the model. ► The magnetism of the compound is mainly determined by the two lowest CF levels.