Magnetic behaviour of nano-particles of Fe2.9Zn0.1O4

DC magnetization measurements are reported in the temperature range 20-300 K on a poly-disperse nano-particle sample of the spinel ferrite Fe2.9Zn0.1O4 with a log-normal size distribution of median diameter 43.6 Angstrom and standard deviation 0.58. Outside a core of ordered spins, moments in surface layer are disordered. Results also show some similarities with conventional spin glasses. Blocking temperature exhibits a near linear variation with two-third power of the applied magnetic field and magnetization M evolves nearly linearly with logarithm of time t. Magnetic anisotropy has been estimated by analysing the M-logt curve. Anisotropy values show a large increase over that of bulk particle samples. Major contribution to this enhancement comes from the disordered surface spins.