Magnetic properties of KY0.93Er0.05Tm0.02(WO4)2 and NaY0.97Er0.02Tm0.01(WO4)2 nanocrystals obtained using Pechini and hydrothermal methods

Abstract

In this study, we investigated potassium- and sodium-yttrium double tungstate nanopowders co-doped with Er3+ and Tm3+ ions in terms of their electron paramagnetic resonance (EPR) and magnetic susceptibility (MS) properties. We compared the magnetic properties of compounds obtained using hydrothermal and Pechini methods followed by calcination at temperatures of 200 °C, and 250 °C, and 700 °C, 750 °C, and 800 °C, respectively. EPR analysis allowed us to determine the spin Hamiltonian parameters and to resolve the local symmetry of the doped ions. Our analysis of the ion symmetry indicated clear differences between the arrangements of the ions in the NaY(WO4)2 and KY(WO4)2 compounds. The temperature dependencies demonstrated the strength and nature of the interactions between the ions, and the relationship was established between the size of the nanoparticles and the Curie–Weiss temperature obtained from the integral intensity of the EPR signal. MS measurements allowed us to verify the EPR results by considering the contributions of co-doped (non-Kramers) ions to the overall magnetic moment.