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

P. Urbanowicz (1) , E. Tomaszewicz (2) , T. Groń (1) , H. Duda (1) , A.W. Pacyna (3) , T. Mydlarz , H. Fuks (1) , S.M. Kaczmarek (1) , J. Krok-Kowalski (1)

1 Institute of Physics
2 Department of Inorganic and Analytical Chemistry
3 PAN - Polska Akademia Nauk = Polish Academy of Sciences = Académie polonaise des sciences

Magnetic susceptibility measurements carried out on (Co,Zn)REWO 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 ZnSmWO and ZnEuWO samples. The temperature independent component of magnetic susceptibility has a negative value for ZnGdWO 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 behaviour with blocking temperature ∼ 30 K, except for ZnEuWO. Fitting procedure of the Landé factor revealed that the stronger orbital contribution, the weaker the superparamagnetic effect, namely for ZnREWO. In case of CoREWO a significant participation of the Co moment in the spontaneous magnetization was observed.

Mots clés: A. Oxides; B. Chemical synthesis; D. Magnetic properties

Domaines: Science des matériaux [cond-mat.mtrl-sci]

P. Urbanowicz, E. Tomaszewicz, T. Groń, H. Duda, A.W. Pacyna, et al.. Superparamagnetic-like behaviour and spin-orbit coupling in (Co,Zn)REWO tungstates (RE=Nd, Sm, Eu, Gd, Dy and Ho). Journal of Physics and Chemistry of Solids, 2011, ⟨10.1016/j.jpcs.2011.04.012⟩. ⟨hal-00757443⟩