Phase and magnetic properties evolutions of Y3−x(CaZr)xFe5−xO12 by the sol-gel method

In this work, Y3−x(CaZr)xFe5−xO12 (CaZr)x:YIG) were prepared by the sol-gel method. High substituted (CaZr)x:YIG nanoparticles with x up to 0.7 were obtained at 1080 °C, below the melting point of Cu electrode. The average sizes calculated by Scherrer formula decreased from 92.4 nm to 70.0 nm when the substitution amount increased from 0 to 0.7, which was consistent with the results of TEM. The sintering temperature required to form pure garnet phase increased from 690 °C to 1065 °C as the substitution amount x increased from 0 to 0.7 for probable homogeneity destruction by Ca2+ and Zr4+. The maximum saturation magnetization (Ms) of 29.8 emu/g was achieved at x=0.3. The enhancement of Ms was attributed to the quantity reduction of Fe3+ in a-site and the increase of net magnetic moment. The observed decline in Ms for the samples with x>0.3 might be attributed to the weakness of super-exchange interaction by changing the angle and length of Fe-O-Fe bonds too much. The complex variations of the coecivities (Hc) indicated the crystal structure from single domain to multiple domains as the sintering temperature increased. Comparing the properties of the samples with x=0 and 0.3, it seemed that the substitution had the influence not only on the formation temperature, but also on the critical size of single domain and the temperature of the critical size emerging.