Magnetic Properties of MgFe₂O₄ Nanoparticles and Zn Doping Effect

抄録

Mg_1-xZn_xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8) nanoparticles encapsulated in amorphous SiO₂ were prepared using a wet chemical method, and their magnetic properties were studied. The diameters of these particles were estimated from X-ray diffraction (XRD) patterns as ranging near 4.5 nm. Magnetization measurements were carried out for all samples under a ±50 kOe field. The blocking temperature T_B was determined to be approximately 20-60 K from the temperature dependence of the field-cooled (FC) and the zero-field-cooled (ZFC) magnetizations. The M-H curve indicated ferromagnetic behavior at 5 K and superparamagnetic (x = 0 － 0.6) and paramagnetic (x = 0.8) behavior at 300 K. The sample with x = 0.4 had the largest maximum magnetization M_S under an applied field of 50 kOe at 5 K, and the sample with x = 0.2 has the largest M_S at 300 K among all the samples.