Nanocrystalline spinel ferrite MFe2O4 (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac)(3), M(acac)(3) (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe2O4 and CoFe2O4 samples contain nanoparticles, whereas the MnFe2O4 and MgFe2O4 samples. consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe2O4 sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe2O4, MnFe2O4 and MgFe2O4 samples, whereas the samples of NiFe2O4 and ZnFe2O4 exhibit a superparamagnetic behavior. (C) 2013 Elsevier Ltd. All rights reserved.