Intriguing complex magnetism of Co in RECoAsO (RE=La, Nd, and Sm)
The bulk intrinsic magnetism of Co changes dramatically when nonmagnetic La Sm and Nd in RECoAsO (RE=La, Nd, Sm). Although the itinerant ferromagnetism occurs below 80-100 K with small saturation moment, typical anti-ferromagnetic (AFM) transitions (TN1, TN2) are observed at 57 K and 45 K for Sm and at 69 K and 14 K for Nd. This is evidenced in isothermal magnetization plots as well. It is clear that Sm/Nd magnetic moments interact with the ordered Co spins in adjacent layer and thus transforms the ferromagnetic (FM) ordering to AFM.