Saturation magnetic properties of Y_3-xRe_x Fe₅O₁₂(Re: Gd, Dy, Nd, Sm and La) nanoparticles grown by a sol-gel method

Re³⁺-substituted garnet nanoparticles _3-x Re_xFe₅ O₁₂(Re = Gd, Dy, Nd, Sm and La) were fabricated by a sol-gel method. The XRD patterns of all samples have only peaks of the garnet structure and the sizes of nanoparticles rang from 34 to 69 nm. Results of VSM show that the saturation magnetization of Y_3-xGd_xFe₅ O₁₂, Y_3-xDy_xFe₅O₁₂ and Y_3-xSm_xFe₅O₁₂ nanoparticles decrease evidently as the Re³⁺ concentration (x) is increased. The saturation magnetization of Y_3-x Nd_xFe₅O₁₂ and Y_3-x La_x Fe₅O₁₂ increases firstly and then decreases as the Re³⁺ concentration (x) is increased. In the meanwhile, it is observed that may be due to the enhancement of the surface spin effects, the saturation magnetization rises as the nanoparticle size is increased.