Structural and magnetic properties of Co–Al substituted Ni ferrites synthesized by co-precipitation method

• Nickel ferrite nanoparticles with different composition are synthesized using co-precipitation method.
• The spinel ferrites are improved by the substitutions of Co+2–Al+3 ions.
• The nanocrystallites are small enough to obtain the suitable signal-to-noise ratio appropriate in the high-density recording media.
• The values of Ms, Hc and Mr are found to be strongly affected by the Co+2–Al+3 contents.

Controlled growth and careful characterizations of nanocrystalline Ni ferrites are demanding for high density recording media. Ferrites of the form Ni(1−x)CoxFe2−x AlxO4 (where x = 0.0, 0.2, 0.4, 0.6 and 0.8) are prepared by the co-precipitation method. The process is investigated with simultaneous thermogravimetric–differential thermal analysis (TG–DTA). The FESEM images display the nanostructural features of the samples with Gaussian distribution and the XRD analysis confirm the formation of single spinel phase with mean particle size 15–19 nm. Our results suggest that these crystallites are small enough to obtain the suitable signal-to-noise ratio appropriate in the high density recording media. The wide variation of saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) evidenced in the range of 31.02–45.56 emu/g, 12.74–19.80 emu/g and 56–563 Oe, respectively are promising for diversified applications. The conduction mechanism is understood using complex impedance measurements. Our simple and economic preparation method may constitute a basis for the production of large scale high quality Ni ferrite nanopowders useful for memory devices.