Magnetic behavior of nickel ferrite–polyethylene nanocomposites synthesized by mechanical milling process

Magnetic properties of nanocrystalline nickel ferrite–polyethylene nanocomposites synthesized by mechanical milling process has been studied by superconducting quantum interference device (SQUID) magnetometer. Both zero-field-cooled (ZFC) and field-cooled (FC) magnetic measurements were made. The absence of hysteresis, remanence, and coercivity at room temperature suggests the superparamagnetic nature of the nanocomposite. The nickel ferrite–polyethylene nanocomposite exhibits a blocking temperature of ∼20 K and does not attain saturation magnetization even at a high field of 50 kOe. The lack of saturation magnetization at high field occurs in association with high field irreversibility and open loop at 50 kOe. This is attributed to the spin-glass like surface layer on the nanocrystalline nickel ferrites with a ferrimagnetically aligned core.