The soft magnetic materials have potential applications in the field of bioengineering as carriers for targeted drug delivery. The magnetic properties, particle size after coating, Curie temperature and its biocompatibility are important parameters for the synthesis of materials. In the present communication cobalt ferrite nanoparticles have been synthesized using co-precipitation method and coated with sodium alginate. The X-ray diffraction and infrared spectroscopic measurements have been used to confirm the ferrite structure formation and coating of the samples with alginate. The SEM micrographs have been used to confirm the particle size which is found to be 45 nm before coating and 78 nm after coating. The saturation magnetization obtained using the hysteresis data for the uncoated cobalt ferrite sample is 19.8 emu/gm while for the coated sample it reduces to 10.2 emu/gm. The AC susceptibility measurements indicate SP structure for the uncoated samples with Curie temperature less than 100℃. The thermo gravimetric measurements have been used to estimate the amount of alginate coating on the sample and it has been correlated with retention of magnetic properties after coating. The value of saturation magnetization reduces after coating due to mass reduction of magnetic material in the sample in accordance with the TGA measurements

Ni-Cu-Zn ferrites with general formula Ni_0.5Zn_0.5-x/2Cu_x/2Fe₂O₄ (with x = 0.3, 0.4, 0.5 and 0.6) have been synthesized using oxalate precursor method with different precursor reaction temperatures in the range 10℃ to 70℃. The Curie temperatures obtained using AC susceptibility measurements are found to be in the range 150℃ to 350℃, the measurements also show single domain structure for all the samples except few compositions obtained at 35℃ precursor reaction temperature, show a multi-domain behaviour. The saturation magnetization is found to be in the range 20 to 51 emu/gm, while the magnetic moment is found to be in the range 0.63 to 1.5 µB. The hysteresis losses were found to be maximum for the samples obtained at precursor reaction temperature of 35℃. The grain size is found to be in the range 0.4 to 2.0 µm