Low temperature Mössbauer and DC magnetization studies in nano-sized Ni substituted Co–Zn ferrites

Studies in the series of nano ferrites pertaining to the stoichiometry NixCo0.5 − xZn0.5Fe2O4, (0≤ x ≤0.5) show that contrary to the trend in bulk Co–Zn and Ni–Zn ferrites, the observed saturation magnetization of Ni–Zn ferrite (x = 0.5) is larger than Co–Zn ferrite (x = 0) and are due to finite size effects. This is evident from calculations which show that the magnetic particle sizes are 1.6 nm for Co–Zn ferrite and 2.4 nm for Ni–Zn whereas their average crystallite sizes are 5 to 3 nm respectively. Low temperature Mössbauer spectroscopic studies show that this can be attributed to an increase in an ordered core with the increase in Ni content which is reflected as a corresponding increase in the saturation magnetization.