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 behaviour with blocking temperature T B a 30 K, * Corresponding author. Email: Tadeusz.Gron@us.edu.pl (T. Groń) 2 except for ZnEu 4 W 3 O 16 . Fitting procedure of the Landé factor revealed that the stronger 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.

Combustion synthesis, structural, magnetic and dielectric properties of Gd3+-doped lead molybdato-tungstates

“…Our studies on electrical and magnetic properties of new tungstates [21][22][23][24][25][26][27][28], molybdates [29][30][31], and molybdato-tungstates [28,32,33] doped with rare earth ions (RE 3+ ) and obtained both in the form of nano-, micropowders, and single crystals have shown that they are non-conductive paramagnetics or superparamagnetics. The reason for this is the strong electron screening on 4f-shells.…”

“…The reason for this is the strong electron screening on 4f-shells. In turn, dielectric spectroscopy studies have shown that these new materials containing additionally d-electron metal ions with unfilled 3d-shells have a bigger capacity for charge accumulation, which is usually accompanied by bigger energy loss [22,23]. Among the paramagnetic rare earth ions, gadolinium ion (Gd 3+ , 4f 5 ) possesses a large magnetic moment due to its isotropic electronic ground state of 7/2 S. Because of the excellent magnetic resonance imaging effect observed for Gd 3+ ions they are used as a common MRI contrast agent [34][35][36].…”

Paramagnetism of Cu_3RE_2W_4O_{18} Semiconductors (RE = Gd, Dy-Er)

“…[6] and J is dened as a sum of an eective angular momentum of RE 3+ ions and the eective spin of Cu 2+ ones. The latter results from the fact that the JLS -coupling works for the protected RE 4f -shell, but not for the unprotected TM 3d-shell [9]. The values of p eff presented in Table show [11], and MPr 2 W 2 O 10 (M = Cd, Co, Mn) [12] ones.…”

“…In all cases above mentioned, the RE 3+ ions are mainly responsible for the paramagnetic state while the inuence of the transition metal (TM) ions on the magnetic properties is slight. The latter strongly inuence on the electronic properties because the TM 3+ ions, as Cu 2+ , Co 2+ , Mn 2+ have both unlled and unscreened 3d-shells [5,9,12].…”

Synthesis and Magnetic Properties of CuCr1.65Se_4Nanoparticles

“…Also a strong spin orbit coupling visible in the large value of the Landé factor g χ = 2.72 may exist, too. A superparamagnetism was not stated in the CuCr 1.65 Se 4 nanoparticles since the magnetization curves were deviated from the universal function of magnetization vs. magnetic eld divided by the temperature [13]. …”