Nanostructured Zn- and Al-doped cobalt spinel ferrites ZnxCo1-xFe2-xAlxO4 (0 ≤ x ≤ 1.0) with particle size in the range of 7–13 nm were synthesized by glycol-thermal reaction. XRD analysis confirmed single-phase cubic spinel structure with no impurity phases. The Mössbauer spectra for Zn- and Al-substituted fine powders could be resolved into two quadrupole doublets associated with 57Fe nuclei in paramagnetic spin phase. An unusual reducing magnetization with increasing particle size has been observed. The field cooled and zero field cooled magnetization measurements show superparamagnetic nanoparticles in the compounds investigated. The blocking temperatures (TB) are sensitive to particle size. Larger particles are blocked at higher temperatures compared to smaller particles at the same field.
- Mössbauer spectra