Superparamagnetic-like behavior and spin–orbit coupling in (Co,Zn)RE4W3O16 tungstates (RE=Nd, Sm, Eu, Gd, Dy and Ho)

Abstract Magnetic susceptibility measurements carried out on (Co,Zn)RE 4 W 3 O 16 compounds revealed a disordered state of magnetic moments above 4.2 K for all compounds under study, and a weak response to magnetic field and temperature for ZnSm 4 W 3 O 16 and ZnEu 4 W 3 O 16 samples. The temperature independent component of magnetic susceptibility has a negative value for ZnGd 4 W 3 O 16 and a positive one for the rest of the tungstates, indicating a domination of van Vleck contribution. The magnetization isotherms of majority of the tungstates under study revealed both spontaneous magnetic moments and hysteresis characteristic for the superparamagnetic-like behavior with blocking temperature T B ∼30 K, except for ZnEu 4 W 3 O 16 . Fitting procedure of the Lande factor revealed that the stronger the orbital contribution, the weaker the superparamagnetic effect, namely for ZnRE 4 W 3 O 16 . In case of CoRE 4 W 3 O 16 a significant participation of the Co 2+ moment in the spontaneous magnetization was observed.