Text this: Mössbauer and Structure-Magnetic Properties Analysis of A<i><sub>y</sub></i>B<sub>1−<i>y</i></sub>C<sub><i>x</i></sub>Fe<sub>2−<i>x</i></sub>O<sub>4</sub> (C=Ho,Gd,Al) Ferrite Nanoparticles Optimized by Doping