Ultrasound induced strain in ultrasmall CoFe2O4@polyvinyl alcohol nanocomposites.

Cobalt ferrite/Polyvinyl alcohol (PVA) nanocomposites were prepared with and without ultrasonic treatment by co-precipitation technique, characterized by X-ray diffraction (XRD), Vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FT-IR) and Transmission Electron Microscopy (TEM). The obtained results revealed that ultrasound irradiation induces strain in the structure and increases the magnetic anisotropy energy of the 7nm magnetic nanoparticles (MNPs). The diffraction peak broadening and shift to lower angle due to the lattice strain were analyzed by means of Williamson-Hall (W-H) method. TEM images also show that ultrasound irradiated sample contain nano-crystallite cobalt ferrite which have completely dispersed and embedded in PVA matrix. These ultrasmall MNPs whit nonzero coercivity are promising for high density data storage devices.