Structural, magnetic and magnetocaloric properties of CoFe 2−x Mo x O 4 (0.0≤ x ≤0.3) ferrites

Abstract We have investigated structural, magnetic and magnetocaloric properties of CoFe 2- x Mo x O 4 (0.0≤ x ≤0.3) ferrites. Polycrystalline samples were prepared by the sol gel method and characterized by the powder X-ray diffraction and scanning electron microscopy. X-ray diffraction patterns show that all samples have a cubic spinel structure and the lattice parameter, a , decreases monotonically with increase in Mo concentration. Scanning electron micrographs indicate that most of the particles are in the range of 400–850 nm size. Magnetic measurements, performed by using a cryogen free vibrating sample magnetometer, show that these samples are soft ferromagnets in the measured temperature range. The saturation magnetization, M s , values of Mo-doped samples are larger than the parent compound with a maximum value of ~106 emu/g for x =0.2 sample. The magnetic entropy change (−Δ S ) increases with increase in applied magnetic field and shows a peak in the vicinity of blocking temperature. A maximum value of 0.56 J kg −1 K −1 at 5 T field has been observed for x =0.2 sample.