Magnetic behavior of nickel–bismuth ferrite synthesized by a combined sol–gel/thermal method

The bulk NiFe2−xBixO4 ferrites with various Bi3+ concentration (x=0, 0.1, 0.15) were synthesized via sol–gel procedure, starting from nickel, bismuth and iron nitrate powders, followed by the conventional thermal treatment. The structural and magnetic properties of the as-prepared ferrites were studied by means of X-ray diffraction, alternating gradient force magnetometry and Faraday balance. The anisotropy constant was determined by the law of approach to saturation (LAS) model. An increasing Bi3+ concentration in NiFe2−xBixO4 leads to a decrease in the saturation magnetization, Néel temperature and the anisotropy constant of the material.