Effect of Ni doping on the properties of fine magnetite particles

Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy are used to characterize the magnetic behaviour of fine magnetite particles obtained from (i) pure goethite and (ii) Ni-doped goethite, in ammoniacal solution. The latter sample has 0.4 wt% Ni which has significantly changed the properties of the sample. The Ni-doped magnetite shows a much higher overoccupancy of tetrahedral sites by iron atoms as compared to the undoped sample. TEM study shows that presence of Ni ions leads to narrower size distribution of magnetite particles as compared to the magnetite obtained from undoped goethite. The coercive field is also affected by presence of Ni, being only 105 Oe for the Ni-doped magnetite as against 170 Oe in the undoped sample.