Anomalous exchange mechanism in Gd monopnictides

Nearest and next nearest neighbor exchange constants I-1 and I-2 were obtained for Gd monopnictides GdXP. Even though relative energy levels are different substantially, lattice constant dependences, as well as the absolute values, are nearly equal to those in Eu chalcogenides EuXC. In particular, strong ferromagnetic I-1 in GdN similar to EuO was explained by the process involving 4f(8) configuration. On the other hand, contrary to electron doped EuXC, no ferromagnetic effect is observed in GdXP due to semimetallic carriers. This is also seen as a weak spin disorder scattering. This anomalous behavior was explained as cancellation of intra and intersite d-f scatterings characteristic to GdXP.