Study on magnetic properties of nanocrystalline La-, Nd-, or Gd-substituted Ni–Mn ferrite at low temperatures

The effects of rare-earth ions with different radii and magnetic moments on the magnetic properties of Ni–Mn ferrite are investigated. X-ray diffraction pattern has shown the presence of cubic structure of spinel ferrite for all samples. The values of Ms and Hc are decreasing with increasing of testing temperatures for all samples. The Hc value of Ni0.7Mn0.3La0.1Fe1.9O4 reaches 1082 Oe at 2 K. Mössbauer spectra tested at 273 K indicate the presence of superparamagnetism for samples calcined at 873 K.