Magnetic properties in Fe-doped NiO synthesized by co-precipitation

Effects of calcining temperature on structural and magnetic properties of nanosized Fe-doped NiO prepared by diol-based sol−gel process

“…In general, the origin of ferromagnetism of Fe-doped NiO results from two main factors: (i) the double exchange interaction through the induced magnetic Fe ions and the defects (e.g., Fe d Ni ) [15,17] and (ii) the presence of ferromagnetic and/or ferrimagnetic impurities co-existed with the main phase [19]. No extra phases were observed in this work, the latter factor was therefore ruled out.…”

“…Interestingly, when Fe ions were doped into NiO, the room-temperature ferromagnetism occurred. So far, a few reports on the magnetic studies of the Fe-doped NiO have been found [15,[17][18][19]. Nan's group [15,17] investigated the magnetism of Fe-doped NiO prepared by a chemical coprecipitation method and post-thermal decomposition process as a function of Fe content (Fe x Ni 1 À x O; x¼0-0.02) and found that the samples doped with Fe exhibited room-temperature ferromagnetism that originated from the double exchange interaction through the induced magnetic Fe ions and charge carriers (from defects).…”

“…However, the origin of roomtemperature ferromagnetism is still in debate. He et al [19] observed the ferromagnetic behavior in Fe-doped NiO bulk ceramics synthesized by the coprecipitation method and reported that ferromagnetism could result from the finite-size effect for the sample with smaller size $ 15 nm (calcined at lower temperature) whereas the origin of ferromagnetism of the sample with larger size $ 60 nm (calcined at higher temperature) could be due to the presence of ferrimagnetic impurity.…”

Effects of ion doping on magnetism of antiferromagnetic nanoparticles

“…In order to change the magnetic properties in AFM nanoparticles they are also doped with various ions. Ferromagnetism with high Curie temperature T C 4 300 K has been observed in ion-doped NiO [2][3][4][5][6][7][8] nanoparticles. The origin of this room temperature ferromagnetism is not explained.…”

“…(3) In the case of similar ionic radii two factors can play a role: (a) different exchange interaction constants J, and/or (b) strong surface anisotropy by the doping ions (for example by Co). (4) FM/AFM exchange coupling between the doping and host ions [16]. An important role here can play electron-phonon or/and spin-phonon interactions, which will be investigated later.…”